[containers] - C++17 → C++20

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@@ -5,28 +5,22 @@
 This Clause describes components that C++ programs may use to organize
 collections of information.
 The following subclauses describe container requirements, and components
 for sequence containers and associative containers, as summarized in
-Table  [[tab:containers.lib.summary]].
-**Table: Containers library summary** <a id="tab:containers.lib.summary">[tab:containers.lib.summary]</a>
 | Subclause                  |                                  | Header                                                       |
-| -------------------------- | -------------------------------- | ----------------- |
 | [[container.requirements]] | Requirements                     |                                                              |
-| [[sequences]]              | Sequence containers              | `<array>` |
-| | | `<deque>` |
-| | | `<forward_list>` |
-| | | `<list>` |
-|                            |                                  | `<vector>` |
-| [[associative]]            | Associative containers           | `<map>`           |
-|                            |                                  | `<set>`           |
-| [[unord]]                  | Unordered associative containers | `<unordered_map>` |
-|                            |                                  | `<unordered_set>` |
-| [[container.adaptors]]     | Container adaptors               | `<queue>`         |
-|                            |                                  | `<stack>`         |
 ## Container requirements <a id="container.requirements">[[container.requirements]]</a>
 ### General container requirements <a id="container.requirements.general">[[container.requirements.general]]</a>
@@ -45,31 +39,31 @@ linear complexity, even though the complexity of copying each contained
 For the components affected by this subclause that declare an
 `allocator_type`, objects stored in these components shall be
 constructed using the function
 `allocator_traits<allocator_type>::rebind_traits<U>::{}construct` and
 destroyed using the function
-`allocator_traits<allocator_type>::rebind_traits<U>::{}destroy` (
-[[allocator.traits.members]]), where `U` is either
 `allocator_type::value_type` or an internal type used by the container.
 These functions are called only for the container’s element type, not
 for internal types used by the container.
 [*Note 1*: This means, for example, that a node-based container might
 need to construct nodes containing aligned buffers and call `construct`
 to place the element into the buffer. — *end note*]
-In Tables  [[tab:containers.container.requirements]],
-[[tab:containers.reversible.requirements]], and
-[[tab:containers.optional.operations]] `X` denotes a container class
-containing objects of type `T`, `a` and `b` denote values of type `X`,
-`u` denotes an identifier, `r` denotes a non-const value of type `X`,
-and `rv` denotes a non-const rvalue of type `X`.
 Those entries marked “(Note A)” or “(Note B)” have linear complexity for
 `array` and have constant complexity for all other standard containers.
-[*Note 2*: The algorithm `equal()` is defined in Clause
 [[algorithms]]. — *end note*]
 The member function `size()` returns the number of elements in the
 container. The number of elements is defined by the rules of
 constructors, inserts, and erases.
@@ -87,10 +81,11 @@ i == j
 i != j
 i < j
 i <= j
 i >= j
 i > j
 i - j
 ```
 where `i` and `j` denote objects of a container’s `iterator` type,
 either or both may be replaced by an object of the container’s
@@ -114,11 +109,11 @@ constructors obtain an allocator by move construction from the allocator
 belonging to the container being moved. Such move construction of the
 allocator shall not exit via an exception. All other constructors for
 these container types take a `const allocator_type&` argument.
 [*Note 4*: If an invocation of a constructor uses the default value of
-an optional allocator argument, then the `Allocator` type must support
 value-initialization. — *end note*]
 A copy of this allocator is used for any memory allocation and element
 construction performed, by these constructors and by all member
 functions, during the lifetime of each container object or until the
@@ -152,13 +147,13 @@ element in one container before the swap shall refer to the same element
 in the other container after the swap. It is unspecified whether an
 iterator with value `a.end()` before the swap will have value `b.end()`
 after the swap.
 If the iterator type of a container belongs to the bidirectional or
-random access iterator categories ([[iterator.requirements]]), the
-container is called *reversible* and satisfies the additional
-requirements in Table  [[tab:containers.reversible.requirements]].
 Unless otherwise specified (see  [[associative.reqmts.except]],
 [[unord.req.except]], [[deque.modifiers]], and [[vector.modifiers]]) all
 container types defined in this Clause meet the following additional
 requirements:
@@ -182,38 +177,40 @@ Unless otherwise specified (either explicitly or by defining a function
 in terms of other functions), invoking a container member function or
 passing a container as an argument to a library function shall not
 invalidate iterators to, or change the values of, objects within that
 container.
-A *contiguous container* is a container that supports random access
-iterators ([[random.access.iterators]]) and whose member types
-`iterator` and `const_iterator` are contiguous iterators (
-[[iterator.requirements.general]]).
-Table  [[tab:containers.optional.operations]] lists operations that are
-provided for some types of containers but not others. Those containers
-for which the listed operations are provided shall implement the
-semantics described in Table  [[tab:containers.optional.operations]]
-unless otherwise stated.
-[*Note 6*: The algorithm `lexicographical_compare()` is defined in
-Clause  [[algorithms]]. — *end note*]
 All of the containers defined in this Clause and in  [[basic.string]]
 except `array` meet the additional requirements of an allocator-aware
-container, as described in Table  [[tab:containers.allocatoraware]].
 Given an allocator type `A` and given a container type `X` having a
 `value_type` identical to `T` and an `allocator_type` identical to
 `allocator_traits<A>::rebind_alloc<T>` and given an lvalue `m` of type
 `A`, a pointer `p` of type `T*`, an expression `v` of type (possibly
 `const`) `T`, and an rvalue `rv` of type `T`, the following terms are
 defined. If `X` is not allocator-aware, the terms below are defined as
 if `A` were `allocator<T>` — no allocator object needs to be created and
 user specializations of `allocator<T>` are not instantiated:
-- `T` is *`DefaultInsertable` into `X`* means that the following
   expression is well-formed:
   ``` cpp
   allocator_traits<A>::construct(m, p)
   ```
 - An element of `X` is *default-inserted* if it is initialized by
@@ -222,71 +219,71 @@ user specializations of `allocator<T>` are not instantiated:
   allocator_traits<A>::construct(m, p)
   ```
   where `p` is the address of the uninitialized storage for the element
   allocated within `X`.
-- `T` is *`MoveInsertable` into `X`* means that the following expression
-  is well-formed:
   ``` cpp
   allocator_traits<A>::construct(m, p, rv)
   ```
   and its evaluation causes the following postcondition to hold: The
   value of `*p` is equivalent to the value of `rv` before the
   evaluation.
   \[*Note 7*: `rv` remains a valid object. Its state is
   unspecified — *end note*]
-- `T` is *`CopyInsertable` into `X`* means that, in addition to `T`
-  being `MoveInsertable` into `X`, the following expression is
   well-formed:
   ``` cpp
   allocator_traits<A>::construct(m, p, v)
   ```
   and its evaluation causes the following postcondition to hold: The
   value of `v` is unchanged and is equivalent to `*p`.
-- `T` is *`EmplaceConstructible` into `X` from `args`*, for zero or more
-  arguments `args`, means that the following expression is well-formed:
   ``` cpp
   allocator_traits<A>::construct(m, p, args)
   ```
-- `T` is *`Erasable` from `X`* means that the following expression is
-  well-formed:
   ``` cpp
   allocator_traits<A>::destroy(m, p)
   ```
 [*Note 8*: A container calls
 `allocator_traits<A>::construct(m, p, args)` to construct an element at
 `p` using `args`, with `m == get_allocator()`. The default `construct`
 in `allocator` will call `::new((void*)p) T(args)`, but specialized
 allocators may choose a different definition. — *end note*]
-In Table  [[tab:containers.allocatoraware]], `X` denotes an
-allocator-aware container class with a `value_type` of `T` using
-allocator of type `A`, `u` denotes a variable, `a` and `b` denote
-non-const lvalues of type `X`, `t` denotes an lvalue or a const rvalue
-of type `X`, `rv` denotes a non-const rvalue of type `X`, and `m` is a
-value of type `A`.
 The behavior of certain container member functions and deduction guides
 depends on whether types qualify as input iterators or allocators. The
 extent to which an implementation determines that a type cannot be an
 input iterator is unspecified, except that as a minimum integral types
 shall not qualify as input iterators. Likewise, the extent to which an
 implementation determines that a type cannot be an allocator is
 unspecified, except that as a minimum a type `A` shall not qualify as an
-allocator unless it satisfies both of the following conditions:
-- The *qualified-id* `A::value_type` is valid and denotes a type (
-  [[temp.deduct]]).
 - The expression `declval<A&>().allocate(size_t{})` is well-formed when
   treated as an unevaluated operand.
 ### Container data races <a id="container.requirements.dataraces">[[container.requirements.dataraces]]</a>
-For purposes of avoiding data races ([[res.on.data.races]]),
 implementations shall consider the following functions to be `const`:
 `begin`, `end`, `rbegin`, `rend`, `front`, `back`, `data`, `find`,
 `lower_bound`, `upper_bound`, `equal_range`, `at` and, except in
 associative or unordered associative containers, `operator[]`.
@@ -312,38 +309,43 @@ which provides limited sequence operations because it has a fixed number
 of elements. The library also provides container adaptors that make it
 easy to construct abstract data types, such as `stack`s or `queue`s, out
 of the basic sequence container kinds (or out of other kinds of sequence
 containers that the user might define).
-The sequence containers offer the programmer different complexity
-trade-offs and should be used accordingly. `vector` or `array` is the
-type of sequence container that should be used by default. `list` or
-`forward_list` should be used when there are frequent insertions and
-deletions from the middle of the sequence. `deque` is the data structure
-of choice when most insertions and deletions take place at the beginning
-or at the end of the sequence.
-In Tables  [[tab:containers.sequence.requirements]] and
-[[tab:containers.sequence.optional]], `X` denotes a sequence container
-class, `a` denotes a value of type `X` containing elements of type `T`,
-`u` denotes the name of a variable being declared, `A` denotes
-`X::allocator_type` if the *qualified-id* `X::allocator_type` is valid
-and denotes a type ([[temp.deduct]]) and `allocator<T>` if it doesn’t,
-`i` and `j` denote iterators satisfying input iterator requirements and
-refer to elements implicitly convertible to `value_type`, `[i, j)`
-denotes a valid range, `il` designates an object of type
-`initializer_list<value_type>`, `n` denotes a value of type
-`X::size_type`, `p` denotes a valid constant iterator to `a`, `q`
-denotes a valid dereferenceable constant iterator to `a`, `[q1, q2)`
-denotes a valid range of constant iterators in `a`, `t` denotes an
-lvalue or a const rvalue of `X::value_type`, and `rv` denotes a
-non-const rvalue of `X::value_type`. `Args` denotes a template parameter
-pack; `args` denotes a function parameter pack with the pattern
-`Args&&`.
 The complexities of the expressions are sequence dependent.
 The iterator returned from `a.insert(p, t)` points to the copy of `t`
 inserted into `a`.
 The iterator returned from `a.insert(p, rv)` points to the copy of `rv`
 inserted into `a`.
@@ -366,12 +368,11 @@ element exists, `a.end()` is returned.
 The iterator returned by `a.erase(q1, q2)` points to the element pointed
 to by `q2` prior to any elements being erased. If no such element
 exists, `a.end()` is returned.
-For every sequence container defined in this Clause and in Clause
-[[strings]]:
 - If the constructor
   ``` cpp
   template<class InputIterator>
     X(InputIterator first, InputIterator last,
@@ -403,32 +404,31 @@ For every sequence container defined in this Clause and in Clause
   and a type that does not qualify as an input iterator is deduced for
   that parameter, or if it has an `Allocator` template parameter and a
   type that does not qualify as an allocator is deduced for that
   parameter.
-Table  [[tab:containers.sequence.optional]] lists operations that are
-provided for some types of sequence containers but not others. An
-implementation shall provide these operations for all container types
-shown in the “container” column, and shall implement them so as to take
-amortized constant time.
 The member function `at()` provides bounds-checked access to container
 elements. `at()` throws `out_of_range` if `n >= a.size()`.
 ### Node handles <a id="container.node">[[container.node]]</a>
-#### `node_handle` overview <a id="container.node.overview">[[container.node.overview]]</a>
 A *node handle* is an object that accepts ownership of a single element
-from an associative container ([[associative.reqmts]]) or an unordered
-associative container ([[unord.req]]). It may be used to transfer that
 ownership to another container with compatible nodes. Containers with
 compatible nodes have the same node handle type. Elements may be
 transferred in either direction between container types in the same row
-of Table  [[tab:containers.node.compat]].
-**Table: Container types with compatible nodes** <a id="tab:containers.node.compat">[tab:containers.node.compat]</a>
 |                                  |                                       |
 | -------------------------------- | ------------------------------------- |
 | `map<K, T, C1, A>`               | `map<K, T, C2, A>`                    |
 | `map<K, T, C1, A>`               | `multimap<K, T, C2, A>`               |
@@ -442,122 +442,126 @@ of Table  [[tab:containers.node.compat]].
 If a node handle is not empty, then it contains an allocator that is
 equal to the allocator of the container when the element was extracted.
 If a node handle is empty, it contains no allocator.
-Class `node_handle` is for exposition only. An implementation is
-permitted to provide equivalent functionality without providing a class
-with this name.
 If a user-defined specialization of `pair` exists for
 `pair<const Key, T>` or `pair<Key, T>`, where `Key` is the container’s
 `key_type` and `T` is the container’s `mapped_type`, the behavior of
 operations involving node handles is undefined.
 ``` cpp
 template<unspecified>
- class node_handle {
 public:
- // These type declarations are described in Tables [tab:containers.associative.requirements] and [tab:HashRequirements].
   using value_type     = see below;     // not present for map containers
   using key_type       = see below;     // not present for set containers
   using mapped_type    = see below;     // not present for set containers
   using allocator_type = see below;
 private:
   using container_node_type = unspecified;
   using ator_traits = allocator_traits<allocator_type>;
- typename ator_traits::rebind_traits<container_node_type>::pointer ptr_;
   optional<allocator_type> alloc_;
 public:
-    constexpr node_handle() noexcept : ptr_(), alloc_() {}
-    ~node_handle();
-    node_handle(node_handle&&) noexcept;
-    node_handle& operator=(node_handle&&);
   value_type& value() const;            // not present for map containers
   key_type& key() const;                // not present for set containers
   mapped_type& mapped() const;          // not present for set containers
   allocator_type get_allocator() const;
   explicit operator bool() const noexcept;
- bool empty() const noexcept;
-    void swap(node_handle&)
     noexcept(ator_traits::propagate_on_container_swap::value ||
              ator_traits::is_always_equal::value);
- friend void swap(node_handle& x, node_handle& y) noexcept(noexcept(x.swap(y))) {
     x.swap(y);
   }
 };
 ```
-#### `node_handle` constructors, copy, and assignment <a id="container.node.cons">[[container.node.cons]]</a>
 ``` cpp
-node_handle(node_handle&& nh) noexcept;
 ```
-*Effects:* Constructs a *`node_handle`* object initializing `ptr_` with
 `nh.ptr_`. Move constructs `alloc_` with `nh.alloc_`. Assigns `nullptr`
 to `nh.ptr_` and assigns `nullopt` to `nh.alloc_`.
 ``` cpp
-node_handle& operator=(node_handle&& nh);
 ```
-*Requires:* Either `!alloc_`, or
-`ator_traits::propagate_on_container_move_assignment` is `true`, or
-`alloc_ == nh.alloc_`.
 *Effects:*
 - If `ptr_ != nullptr`, destroys the `value_type` subobject in the
   `container_node_type` object pointed to by `ptr_` by calling
   `ator_traits::destroy`, then deallocates `ptr_` by calling
-  `ator_traits::rebind_traits<container_node_type>::deallocate`.
 - Assigns `nh.ptr_` to `ptr_`.
-- If `!alloc` or `ator_traits::propagate_on_container_move_assignment`
- is `true`, move assigns `nh.alloc_` to `alloc_`.
 - Assigns `nullptr` to `nh.ptr_` and assigns `nullopt` to `nh.alloc_`.
 *Returns:* `*this`.
 *Throws:* Nothing.
-#### `node_handle` destructor <a id="container.node.dtor">[[container.node.dtor]]</a>
 ``` cpp
-~node_handle();
 ```
 *Effects:* If `ptr_ != nullptr`, destroys the `value_type` subobject in
 the `container_node_type` object pointed to by `ptr_` by calling
 `ator_traits::destroy`, then deallocates `ptr_` by calling
-`ator_traits::rebind_traits<container_node_type>::deallocate`.
-#### `node_handle` observers <a id="container.node.observers">[[container.node.observers]]</a>
 ``` cpp
 value_type& value() const;
 ```
-*Requires:* `empty() == false`.
 *Returns:* A reference to the `value_type` subobject in the
 `container_node_type` object pointed to by `ptr_`.
 *Throws:* Nothing.
 ``` cpp
 key_type& key() const;
 ```
-*Requires:* `empty() == false`.
 *Returns:* A non-const reference to the `key_type` member of the
 `value_type` subobject in the `container_node_type` object pointed to by
 `ptr_`.
@@ -568,22 +572,22 @@ permitted.
 ``` cpp
 mapped_type& mapped() const;
 ```
-*Requires:* `empty() == false`.
 *Returns:* A reference to the `mapped_type` member of the `value_type`
 subobject in the `container_node_type` object pointed to by `ptr_`.
 *Throws:* Nothing.
 ``` cpp
 allocator_type get_allocator() const;
 ```
-*Requires:* `empty() == false`.
 *Returns:* `*alloc_`.
 *Throws:* Nothing.
@@ -592,70 +596,75 @@ explicit operator bool() const noexcept;
 ```
 *Returns:* `ptr_ != nullptr`.
 ``` cpp
-bool empty() const noexcept;
 ```
 *Returns:* `ptr_ == nullptr`.
-#### `node_handle` modifiers <a id="container.node.modifiers">[[container.node.modifiers]]</a>
 ``` cpp
-void swap(node_handle& nh)
   noexcept(ator_traits::propagate_on_container_swap::value ||
            ator_traits::is_always_equal::value);
 ```
-*Requires:* `!alloc_`, or `!nh.alloc_`, or
-`ator_traits::propagate_on_container_swap` is `true`, or
 `alloc_ == nh.alloc_`.
 *Effects:* Calls `swap(ptr_, nh.ptr_)`. If `!alloc_`, or `!nh.alloc_`,
-or `ator_traits::propagate_on_container_swap` is `true` calls
 `swap(alloc_, nh.alloc_)`.
 ### Insert return type <a id="container.insert.return">[[container.insert.return]]</a>
 The associative containers with unique keys and the unordered containers
 with unique keys have a member function `insert` that returns a nested
 type `insert_return_type`. That return type is a specialization of the
-type specified in this subclause.
 ``` cpp
 template<class Iterator, class NodeType>
-struct INSERT_RETURN_TYPE
 {
   Iterator position;
   bool     inserted;
   NodeType node;
 };
 ```
-The name `INSERT_RETURN_TYPE` is exposition only. `INSERT_RETURN_TYPE`
-has the template parameters, data members, and special members specified
-above. It has no base classes or members other than those specified.
 ### Associative containers <a id="associative.reqmts">[[associative.reqmts]]</a>
 Associative containers provide fast retrieval of data based on keys. The
 library provides four basic kinds of associative containers: `set`,
 `multiset`, `map` and `multimap`.
 Each associative container is parameterized on `Key` and an ordering
-relation `Compare` that induces a strict weak ordering (
-[[alg.sorting]]) on elements of `Key`. In addition, `map` and `multimap`
-associate an arbitrary *mapped type* `T` with the `Key`. The object of
-type `Compare` is called the *comparison object* of a container.
 The phrase “equivalence of keys” means the equivalence relation imposed
-by the comparison and *not* the `operator==` on keys. That is, two keys
-`k1` and `k2` are considered to be equivalent if for the comparison
-object `comp`, `comp(k1, k2) == false && comp(k2, k1) == false`. For any
-two keys `k1` and `k2` in the same container, calling `comp(k1, k2)`
-shall always return the same value.
 An associative container supports *unique keys* if it may contain at
 most one element for each key. Otherwise, it supports *equivalent keys*.
 The `set` and `map` classes support unique keys; the `multiset` and
 `multimap` classes support equivalent keys. For `multiset` and
@@ -671,45 +680,44 @@ of an associative container is of the bidirectional iterator category.
 For associative containers where the value type is the same as the key
 type, both `iterator` and `const_iterator` are constant iterators. It is
 unspecified whether or not `iterator` and `const_iterator` are the same
 type.
-[*Note 1*: `iterator` and `const_iterator` have identical semantics in
 this case, and `iterator` is convertible to `const_iterator`. Users can
 avoid violating the one-definition rule by always using `const_iterator`
 in their function parameter lists. — *end note*]
 The associative containers meet all the requirements of Allocator-aware
-containers ([[container.requirements.general]]), except that for `map`
-and `multimap`, the requirements placed on `value_type` in Table
-[[tab:containers.container.requirements]] apply instead to `key_type`
-and `mapped_type`.
-[*Note 2*: For example, in some cases `key_type` and `mapped_type` are
-required to be `CopyAssignable` even though the associated `value_type`,
-`pair<const key_type, mapped_type>`, is not
-`CopyAssignable`. — *end note*]
-In Table  [[tab:containers.associative.requirements]], `X` denotes an
-associative container class, `a` denotes a value of type `X`, `a2`
-denotes a value of a type with nodes compatible with type `X` (Table
-[[tab:containers.node.compat]]), `b` denotes a possibly `const` value of
-type `X`, `u` denotes the name of a variable being declared, `a_uniq`
-denotes a value of type `X` when `X` supports unique keys, `a_eq`
-denotes a value of type `X` when `X` supports multiple keys, `a_tran`
-denotes a possibly `const` value of type `X` when the *qualified-id*
-`X::key_compare::is_transparent` is valid and denotes a type (
-[[temp.deduct]]), `i` and `j` satisfy input iterator requirements and
-refer to elements implicitly convertible to `value_type`, \[`i`, `j`)
-denotes a valid range, `p` denotes a valid constant iterator to `a`, `q`
-denotes a valid dereferenceable constant iterator to `a`, `r` denotes a
-valid dereferenceable iterator to `a`, `[q1, q2)` denotes a valid range
-of constant iterators in `a`, `il` designates an object of type
 `initializer_list<value_type>`, `t` denotes a value of type
 `X::value_type`, `k` denotes a value of type `X::key_type` and `c`
 denotes a possibly `const` value of type `X::key_compare`; `kl` is a
-value such that `a` is partitioned ([[alg.sorting]]) with respect to
 `c(r, kl)`, with `r` the key value of `e` and `e` in `a`; `ku` is a
 value such that `a` is partitioned with respect to `!c(ku, r)`; `ke` is
 a value such that `a` is partitioned with respect to `c(r, ke)` and
 `!c(ke, r)`, with `c(r, ke)` implying `!c(ke, r)`. `A` denotes the
 storage allocator used by `X`, if any, or `allocator<X::value_type>`
@@ -746,19 +754,19 @@ value_comp(*i, *j) != false
 ```
 When an associative container is constructed by passing a comparison
 object the container shall not store a pointer or reference to the
 passed object, even if that object is passed by reference. When an
-associative container is copied, either through a copy constructor or an
 assignment operator, the target container shall then use the comparison
 object from the container being copied, as if that comparison object had
 been passed to the target container in its constructor.
-The member function templates `find`, `count`, `lower_bound`,
-`upper_bound`, and `equal_range` shall not participate in overload
-resolution unless the *qualified-id* `Compare::is_transparent` is valid
-and denotes a type ([[temp.deduct]]).
 A deduction guide for an associative container shall not participate in
 overload resolution if any of the following are true:
 - It has an `InputIterator` template parameter and a type that does not
@@ -789,31 +797,31 @@ of data based on keys. The worst-case complexity for most operations is
 linear, but the average case is much faster. The library provides four
 unordered associative containers: `unordered_set`, `unordered_map`,
 `unordered_multiset`, and `unordered_multimap`.
 Unordered associative containers conform to the requirements for
-Containers ([[container.requirements]]), except that the expressions
 `a == b` and `a != b` have different semantics than for the other
 container types.
 Each unordered associative container is parameterized by `Key`, by a
-function object type `Hash` that meets the `Hash` requirements (
-[[hash.requirements]]) and acts as a hash function for argument values
-of type `Key`, and by a binary predicate `Pred` that induces an
-equivalence relation on values of type `Key`. Additionally,
-`unordered_map` and `unordered_multimap` associate an arbitrary *mapped
-type* `T` with the `Key`.
 The container’s object of type `Hash` — denoted by `hash` — is called
 the *hash function* of the container. The container’s object of type
 `Pred` — denoted by `pred` — is called the *key equality predicate* of
 the container.
-Two values `k1` and `k2` of type `Key` are considered equivalent if the
-container’s key equality predicate returns `true` when passed those
-values. If `k1` and `k2` are equivalent, the container’s hash function
-shall return the same value for both.
 [*Note 1*: Thus, when an unordered associative container is
 instantiated with a non-default `Pred` parameter it usually needs a
 non-default `Hash` parameter as well. — *end note*]
@@ -858,64 +866,78 @@ changes ordering between elements, and changes which buckets elements
 appear in, but does not invalidate pointers or references to elements.
 For `unordered_multiset` and `unordered_multimap`, rehashing preserves
 the relative ordering of equivalent elements.
 The unordered associative containers meet all the requirements of
-Allocator-aware containers ([[container.requirements.general]]), except
 that for `unordered_map` and `unordered_multimap`, the requirements
-placed on `value_type` in Table
-[[tab:containers.container.requirements]] apply instead to `key_type`
-and `mapped_type`.
 [*Note 3*: For example, `key_type` and `mapped_type` are sometimes
-required to be `CopyAssignable` even though the associated `value_type`,
-`pair<const key_type, mapped_type>`, is not
-`CopyAssignable`. — *end note*]
-In Table  [[tab:HashRequirements]]: `X` denotes an unordered associative
-container class, `a` denotes a value of type `X`, `a2` denotes a value
-of a type with nodes compatible with type `X` (Table
-[[tab:containers.node.compat]]), `b` denotes a possibly const value of
-type `X`, `a_uniq` denotes a value of type `X` when `X` supports unique
-keys, `a_eq` denotes a value of type `X` when `X` supports equivalent
-keys, `i` and `j` denote input iterators that refer to `value_type`,
-`[i, j)` denotes a valid range, `p` and `q2` denote valid constant
-iterators to `a`, `q` and `q1` denote valid dereferenceable constant
-iterators to `a`, `r` denotes a valid dereferenceable iterator to `a`,
-`[q1, q2)` denotes a valid range in `a`, `il` denotes a value of type
-`initializer_list<value_type>`, `t` denotes a value of type
-`X::value_type`, `k` denotes a value of type `key_type`, `hf` denotes a
-possibly const value of type `hasher`, `eq` denotes a possibly const
-value of type `key_equal`, `n` denotes a value of type `size_type`, `z`
-denotes a value of type `float`, and `nh` denotes a non-const rvalue of
-type `X::node_type`.
 Two unordered containers `a` and `b` compare equal if
 `a.size() == b.size()` and, for every equivalent-key group \[`Ea1`,
 `Ea2`) obtained from `a.equal_range(Ea1)`, there exists an
 equivalent-key group \[`Eb1`, `Eb2`) obtained from `b.equal_range(Ea1)`,
 such that `is_permutation(Ea1, Ea2, Eb1, Eb2)` returns `true`. For
 `unordered_set` and `unordered_map`, the complexity of `operator==`
 (i.e., the number of calls to the `==` operator of the `value_type`, to
 the predicate returned by `key_eq()`, and to the hasher returned by
 `hash_function()`) is proportional to N in the average case and to N² in
-the worst case, where N is a.size(). For `unordered_multiset` and
 `unordered_multimap`, the complexity of `operator==` is proportional to
 $\sum E_i^2$ in the average case and to N² in the worst case, where N is
 `a.size()`, and Eᵢ is the size of the iᵗʰ equivalent-key group in `a`.
 However, if the respective elements of each corresponding pair of
 equivalent-key groups Eaᵢ and Ebᵢ are arranged in the same order (as is
 commonly the case, e.g., if `a` and `b` are unmodified copies of the
 same container), then the average-case complexity for
 `unordered_multiset` and `unordered_multimap` becomes proportional to N
 (but worst-case complexity remains 𝑂(N^2), e.g., for a pathologically
 bad hash function). The behavior of a program that uses `operator==` or
-`operator!=` on unordered containers is undefined unless the `Hash` and
-`Pred` function objects respectively have the same behavior for both
-containers and the equality comparison function for `Key` is a
-refinement[^1] of the partition into equivalent-key groups produced by
-`Pred`.
 The iterator types `iterator` and `const_iterator` of an unordered
 associative container are of at least the forward iterator category. For
 unordered associative containers where the key type and value type are
 the same, both `iterator` and `const_iterator` are constant iterators.
@@ -938,10 +960,15 @@ pointers and references to the removed element remain valid. However,
 accessing the element through such pointers and references while the
 element is owned by a `node_type` is undefined behavior. References and
 pointers to an element obtained while it is owned by a `node_type` are
 invalidated if the element is successfully inserted.
 A deduction guide for an unordered associative container shall not
 participate in overload resolution if any of the following are true:
 - It has an `InputIterator` template parameter and a type that does not
   qualify as an input iterator is deduced for that parameter.
@@ -977,35 +1004,47 @@ or comparison function, the `rehash()` function has no effect.
 The headers `<array>`, `<deque>`, `<forward_list>`, `<list>`, and
 `<vector>` define class templates that meet the requirements for
 sequence containers.
 ### Header `<array>` synopsis <a id="array.syn">[[array.syn]]</a>
 ``` cpp
-#include <initializer_list>
 namespace std {
   // [array], class template array
   template<class T, size_t N> struct array;
   template<class T, size_t N>
-    bool operator==(const array<T, N>& x, const array<T, N>& y);
-  template <class T, size_t N>
-    bool operator!=(const array<T, N>& x, const array<T, N>& y);
-  template <class T, size_t N>
-    bool operator< (const array<T, N>& x, const array<T, N>& y);
   template<class T, size_t N>
- bool operator> (const array<T, N>& x, const array<T, N>& y);
   template<class T, size_t N>
- bool operator<=(const array<T, N>& x, const array<T, N>& y);
   template<class T, size_t N>
- bool operator>=(const array<T, N>& x, const array<T, N>& y);
   template<class T, size_t N>
- void swap(array<T, N>& x, array<T, N>& y) noexcept(noexcept(x.swap(y)));
- template <class T> class tuple_size;
-  template <size_t I, class T> class tuple_element;
   template<class T, size_t N>
     struct tuple_size<array<T, N>>;
   template<size_t I, class T, size_t N>
     struct tuple_element<I, array<T, N>>;
   template<size_t I, class T, size_t N>
@@ -1020,124 +1059,136 @@ namespace std {
 ```
 ### Header `<deque>` synopsis <a id="deque.syn">[[deque.syn]]</a>
 ``` cpp
-#include <initializer_list>
 namespace std {
   // [deque], class template deque
   template<class T, class Allocator = allocator<T>> class deque;
   template<class T, class Allocator>
     bool operator==(const deque<T, Allocator>& x, const deque<T, Allocator>& y);
   template<class T, class Allocator>
- bool operator< (const deque<T, Allocator>& x, const deque<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator!=(const deque<T, Allocator>& x, const deque<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator> (const deque<T, Allocator>& x, const deque<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator>=(const deque<T, Allocator>& x, const deque<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator<=(const deque<T, Allocator>& x, const deque<T, Allocator>& y);
   template<class T, class Allocator>
     void swap(deque<T, Allocator>& x, deque<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
   namespace pmr {
     template<class T>
       using deque = std::deque<T, polymorphic_allocator<T>>;
   }
 }
 ```
-### Header `<forward_list>` synopsis <a id="forward_list.syn">[[forward_list.syn]]</a>
 ``` cpp
-#include <initializer_list>
 namespace std {
   // [forwardlist], class template forward_list
   template<class T, class Allocator = allocator<T>> class forward_list;
   template<class T, class Allocator>
     bool operator==(const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
   template<class T, class Allocator>
- bool operator< (const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator!=(const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator> (const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator>=(const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator<=(const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
   template<class T, class Allocator>
     void swap(forward_list<T, Allocator>& x, forward_list<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
   namespace pmr {
     template<class T>
       using forward_list = std::forward_list<T, polymorphic_allocator<T>>;
   }
 }
 ```
 ### Header `<list>` synopsis <a id="list.syn">[[list.syn]]</a>
 ``` cpp
-#include <initializer_list>
 namespace std {
   // [list], class template list
   template<class T, class Allocator = allocator<T>> class list;
   template<class T, class Allocator>
     bool operator==(const list<T, Allocator>& x, const list<T, Allocator>& y);
   template<class T, class Allocator>
- bool operator< (const list<T, Allocator>& x, const list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator!=(const list<T, Allocator>& x, const list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator> (const list<T, Allocator>& x, const list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator>=(const list<T, Allocator>& x, const list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator<=(const list<T, Allocator>& x, const list<T, Allocator>& y);
   template<class T, class Allocator>
     void swap(list<T, Allocator>& x, list<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
   namespace pmr {
     template<class T>
       using list = std::list<T, polymorphic_allocator<T>>;
   }
 }
 ```
 ### Header `<vector>` synopsis <a id="vector.syn">[[vector.syn]]</a>
 ``` cpp
-#include <initializer_list>
 namespace std {
   // [vector], class template vector
   template<class T, class Allocator = allocator<T>> class vector;
   template<class T, class Allocator>
-    bool operator==(const vector<T, Allocator>& x, const vector<T, Allocator>& y);
   template<class T, class Allocator>
- bool operator< (const vector<T, Allocator>& x, const vector<T, Allocator>& y);
   template<class T, class Allocator>
- bool operator!=(const vector<T, Allocator>& x, const vector<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator> (const vector<T, Allocator>& x, const vector<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator>=(const vector<T, Allocator>& x, const vector<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator<=(const vector<T, Allocator>& x, const vector<T, Allocator>& y);
-  template <class T, class Allocator>
-    void swap(vector<T, Allocator>& x, vector<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
   // [vector.bool], class vector<bool>
   template<class Allocator> class vector<bool, Allocator>;
   // hash support
   template<class T> struct hash;
@@ -1150,35 +1201,44 @@ namespace std {
 }
 ```
 ### Class template `array` <a id="array">[[array]]</a>
-#### Class template `array` overview <a id="array.overview">[[array.overview]]</a>
 The header `<array>` defines a class template for storing fixed-size
-sequences of objects. An `array` is a contiguous container (
-[[container.requirements.general]]). An instance of `array<T, N>` stores
 `N` elements of type `T`, so that `size() == N` is an invariant.
-An `array` is an aggregate ([[dcl.init.aggr]]) that can be
 list-initialized with up to `N` elements whose types are convertible to
 `T`.
-An `array` satisfies all of the requirements of a container and of a
-reversible container ([[container.requirements]]), except that a
-default constructed `array` object is not empty and that `swap` does not
-have constant complexity. An `array` satisfies some of the requirements
-of a sequence container ([[sequence.reqmts]]). Descriptions are
-provided here only for operations on `array` that are not described in
-one of these tables and for operations where there is additional
-semantic information.
 ``` cpp
 namespace std {
   template<class T, size_t N>
   struct array {
-    // types:
     using value_type             = T;
     using pointer                = T*;
     using const_pointer          = const T*;
     using reference              = T&;
     using const_reference        = const T&;
@@ -1189,14 +1249,14 @@ namespace std {
     using reverse_iterator       = std::reverse_iterator<iterator>;
     using const_reverse_iterator = std::reverse_iterator<const_iterator>;
     // no explicit construct/copy/destroy for aggregate type
-    void fill(const T& u);
-    void swap(array&) noexcept(is_nothrow_swappable_v<T>);
-    // iterators:
     constexpr iterator               begin() noexcept;
     constexpr const_iterator         begin() const noexcept;
     constexpr iterator               end() noexcept;
     constexpr const_iterator         end() const noexcept;
@@ -1208,16 +1268,16 @@ namespace std {
     constexpr const_iterator         cbegin() const noexcept;
     constexpr const_iterator         cend() const noexcept;
     constexpr const_reverse_iterator crbegin() const noexcept;
     constexpr const_reverse_iterator crend() const noexcept;
-    // capacity:
-    constexpr bool empty() const noexcept;
     constexpr size_type size() const noexcept;
     constexpr size_type max_size() const noexcept;
-    // element access:
     constexpr reference       operator[](size_type n);
     constexpr const_reference operator[](size_type n) const;
     constexpr reference       at(size_type n);
     constexpr const_reference at(size_type n) const;
     constexpr reference       front();
@@ -1232,83 +1292,75 @@ namespace std {
   template<class T, class... U>
     array(T, U...) -> array<T, 1 + sizeof...(U)>;
 }
 ```
-#### `array` constructors, copy, and assignment <a id="array.cons">[[array.cons]]</a>
-The conditions for an aggregate ([[dcl.init.aggr]]) shall be met. Class
 `array` relies on the implicitly-declared special member functions (
-[[class.ctor]], [[class.dtor]], and [[class.copy]]) to conform to the
-container requirements table in  [[container.requirements]]. In addition
-to the requirements specified in the container requirements table, the
-implicit move constructor and move assignment operator for `array`
-require that `T` be `MoveConstructible` or `MoveAssignable`,
-respectively.
 ``` cpp
 template<class T, class... U>
   array(T, U...) -> array<T, 1 + sizeof...(U)>;
 ```
-*Requires:* `(is_same_v<T, U> && ...)` is `true`. Otherwise the program
-is ill-formed.
-#### `array` specialized algorithms <a id="array.special">[[array.special]]</a>
 ``` cpp
-template <class T, size_t N>
-  void swap(array<T, N>& x, array<T, N>& y) noexcept(noexcept(x.swap(y)));
-```
-*Remarks:* This function shall not participate in overload resolution
-unless `N == 0` or `is_swappable_v<T>` is `true`.
-*Effects:* As if by `x.swap(y)`.
-*Complexity:* Linear in `N`.
-#### `array::size` <a id="array.size">[[array.size]]</a>
-``` cpp
-template <class T, size_t N> constexpr size_type array<T, N>::size() const noexcept;
 ```
 *Returns:* `N`.
-#### `array::data` <a id="array.data">[[array.data]]</a>
 ``` cpp
 constexpr T* data() noexcept;
 constexpr const T* data() const noexcept;
 ```
-*Returns:* A pointer such that `data() == addressof(front())`, and
-\[`data()`, `data() + size()`) is a valid range.
-#### `array::fill` <a id="array.fill">[[array.fill]]</a>
 ``` cpp
-void fill(const T& u);
 ```
 *Effects:* As if by `fill_n(begin(), N, u)`.
-#### `array::swap` <a id="array.swap">[[array.swap]]</a>
 ``` cpp
-void swap(array& y) noexcept(is_nothrow_swappable_v<T>);
 ```
 *Effects:* Equivalent to `swap_ranges(begin(), end(), y.begin())`.
 [*Note 1*: Unlike the `swap` function for other containers,
 `array::swap` takes linear time, may exit via an exception, and does not
 cause iterators to become associated with the other
 container. — *end note*]
-#### Zero sized arrays <a id="array.zero">[[array.zero]]</a>
 `array` shall provide support for the special case `N == 0`.
 In the case that `N == 0`, `begin() == end() ==` unique value. The
 return value of `data()` is unspecified.
@@ -1317,24 +1369,51 @@ The effect of calling `front()` or `back()` for a zero-sized array is
 undefined.
 Member function `swap()` shall have a non-throwing exception
 specification.
-#### Tuple interface to class template `array` <a id="array.tuple">[[array.tuple]]</a>
 ``` cpp
 template<class T, size_t N>
   struct tuple_size<array<T, N>> : integral_constant<size_t, N> { };
 ```
 ``` cpp
-tuple_element<I, array<T, N>>::type
 ```
-*Requires:* `I < N`. The program is ill-formed if `I` is out of bounds.
-*Value:* The type T.
 ``` cpp
 template<size_t I, class T, size_t N>
   constexpr T& get(array<T, N>& a) noexcept;
 template<size_t I, class T, size_t N>
@@ -1343,41 +1422,40 @@ template <size_t I, class T, size_t N>
   constexpr const T& get(const array<T, N>& a) noexcept;
 template<size_t I, class T, size_t N>
   constexpr const T&& get(const array<T, N>&& a) noexcept;
 ```
-*Requires:* `I < N`. The program is ill-formed if `I` is out of bounds.
-*Returns:* A reference to the `I`th element of `a`, where indexing is
 zero-based.
 ### Class template `deque` <a id="deque">[[deque]]</a>
-#### Class template `deque` overview <a id="deque.overview">[[deque.overview]]</a>
 A `deque` is a sequence container that supports random access iterators
-([[random.access.iterators]]). In addition, it supports constant time
 insert and erase operations at the beginning or the end; insert and
 erase in the middle take linear time. That is, a deque is especially
 optimized for pushing and popping elements at the beginning and end.
 Storage management is handled automatically.
-A `deque` satisfies all of the requirements of a container, of a
-reversible container (given in tables in  [[container.requirements]]),
-of a sequence container, including the optional sequence container
-requirements ([[sequence.reqmts]]), and of an allocator-aware container
-(Table  [[tab:containers.allocatoraware]]). Descriptions are provided
-here only for operations on `deque` that are not described in one of
-these tables or for operations where there is additional semantic
-information.
 ``` cpp
 namespace std {
   template<class T, class Allocator = allocator<T>>
   class deque {
   public:
-    // types:
     using value_type             = T;
     using allocator_type         = Allocator;
     using pointer                = typename allocator_traits<Allocator>::pointer;
     using const_pointer          = typename allocator_traits<Allocator>::const_pointer;
     using reference              = value_type&;
@@ -1411,11 +1489,11 @@ namespace std {
       void assign(InputIterator first, InputIterator last);
     void assign(size_type n, const T& t);
     void assign(initializer_list<T>);
     allocator_type get_allocator() const noexcept;
-    // iterators:
     iterator               begin() noexcept;
     const_iterator         begin() const noexcept;
     iterator               end() noexcept;
     const_iterator         end() const noexcept;
     reverse_iterator       rbegin() noexcept;
@@ -1427,18 +1505,18 @@ namespace std {
     const_iterator         cend() const noexcept;
     const_reverse_iterator crbegin() const noexcept;
     const_reverse_iterator crend() const noexcept;
     // [deque.capacity], capacity
-    bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
     void      resize(size_type sz);
     void      resize(size_type sz, const T& c);
     void      shrink_to_fit();
-    // element access:
     reference       operator[](size_type n);
     const_reference operator[](size_type n) const;
     reference       at(size_type n);
     const_reference at(size_type n) const;
     reference       front();
@@ -1471,36 +1549,22 @@ namespace std {
     void     swap(deque&)
       noexcept(allocator_traits<Allocator>::is_always_equal::value);
     void     clear() noexcept;
   };
-  template<class InputIterator,
-           class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
     deque(InputIterator, InputIterator, Allocator = Allocator())
-      -> deque<typename iterator_traits<InputIterator>::value_type, Allocator>;
- template <class T, class Allocator>
-    bool operator==(const deque<T, Allocator>& x, const deque<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator< (const deque<T, Allocator>& x, const deque<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator!=(const deque<T, Allocator>& x, const deque<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator> (const deque<T, Allocator>& x, const deque<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator>=(const deque<T, Allocator>& x, const deque<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator<=(const deque<T, Allocator>& x, const deque<T, Allocator>& y);
-  // [deque.special], specialized algorithms
   template<class T, class Allocator>
     void swap(deque<T, Allocator>& x, deque<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
-#### `deque` constructors, copy, and assignment <a id="deque.cons">[[deque.cons]]</a>
 ``` cpp
 explicit deque(const Allocator&);
 ```
@@ -1513,22 +1577,22 @@ explicit deque(size_type n, const Allocator& = Allocator());
 ```
 *Effects:* Constructs a `deque` with `n` default-inserted elements using
 the specified allocator.
-*Requires:* `T` shall be `DefaultInsertable` into `*this`.
 *Complexity:* Linear in `n`.
 ``` cpp
 deque(size_type n, const T& value, const Allocator& = Allocator());
 ```
 *Effects:* Constructs a `deque` with `n` copies of `value`, using the
 specified allocator.
-*Requires:* `T` shall be `CopyInsertable` into `*this`.
 *Complexity:* Linear in `n`.
 ``` cpp
 template<class InputIterator>
@@ -1538,55 +1602,57 @@ template <class InputIterator>
 *Effects:* Constructs a `deque` equal to the range \[`first`, `last`),
 using the specified allocator.
 *Complexity:* Linear in `distance(first, last)`.
-#### `deque` capacity <a id="deque.capacity">[[deque.capacity]]</a>
 ``` cpp
 void resize(size_type sz);
 ```
 *Effects:* If `sz < size()`, erases the last `size() - sz` elements from
 the sequence. Otherwise, appends `sz - size()` default-inserted elements
 to the sequence.
-*Requires:* `T` shall be `MoveInsertable` and `DefaultInsertable` into
-`*this`.
 ``` cpp
 void resize(size_type sz, const T& c);
 ```
 *Effects:* If `sz < size()`, erases the last `size() - sz` elements from
 the sequence. Otherwise, appends `sz - size()` copies of `c` to the
 sequence.
-*Requires:* `T` shall be `CopyInsertable` into `*this`.
 ``` cpp
 void shrink_to_fit();
 ```
-*Requires:* `T` shall be `MoveInsertable` into `*this`.
 *Effects:* `shrink_to_fit` is a non-binding request to reduce memory use
 but does not change the size of the sequence.
 [*Note 1*: The request is non-binding to allow latitude for
 implementation-specific optimizations. — *end note*]
-If an exception is thrown other than by the move constructor of a
-non-`CopyInsertable` `T` there are no effects.
-*Complexity:* Linear in the size of the sequence.
-*Remarks:* `shrink_to_fit` invalidates all the references, pointers, and
-iterators referring to the elements in the sequence as well as the
-past-the-end iterator.
-#### `deque` modifiers <a id="deque.modifiers">[[deque.modifiers]]</a>
 ``` cpp
 iterator insert(const_iterator position, const T& x);
 iterator insert(const_iterator position, T&& x);
 iterator insert(const_iterator position, size_type n, const T& x);
@@ -1611,16 +1677,16 @@ has no effect on the validity of references to elements of the deque.
 *Remarks:* If an exception is thrown other than by the copy constructor,
 move constructor, assignment operator, or move assignment operator of
 `T` there are no effects. If an exception is thrown while inserting a
 single element at either end, there are no effects. Otherwise, if an
-exception is thrown by the move constructor of a non-`CopyInsertable`
-`T`, the effects are unspecified.
 *Complexity:* The complexity is linear in the number of elements
 inserted plus the lesser of the distances to the beginning and end of
-the deque. Inserting a single element either at the beginning or end of
 a deque always takes constant time and causes a single call to a
 constructor of `T`.
 ``` cpp
 iterator erase(const_iterator position);
@@ -1645,48 +1711,68 @@ operations. — *end note*]
 as the number of elements erased, but the number of calls to the
 assignment operator of `T` is no more than the lesser of the number of
 elements before the erased elements and the number of elements after the
 erased elements.
-*Throws:* Nothing unless an exception is thrown by the copy constructor,
-move constructor, assignment operator, or move assignment operator of
-`T`.
-#### `deque` specialized algorithms <a id="deque.special">[[deque.special]]</a>
 ``` cpp
-template <class T, class Allocator>
- void swap(deque<T, Allocator>& x, deque<T, Allocator>& y)
- noexcept(noexcept(x.swap(y)));
 ```
-*Effects:* As if by `x.swap(y)`.
 ### Class template `forward_list` <a id="forwardlist">[[forwardlist]]</a>
-#### Class template `forward_list` overview <a id="forwardlist.overview">[[forwardlist.overview]]</a>
 A `forward_list` is a container that supports forward iterators and
 allows constant time insert and erase operations anywhere within the
 sequence, with storage management handled automatically. Fast random
 access to list elements is not supported.
 [*Note 1*: It is intended that `forward_list` have zero space or time
 overhead relative to a hand-written C-style singly linked list. Features
 that would conflict with that goal have been omitted. — *end note*]
-A `forward_list` satisfies all of the requirements of a container
-(Table  [[tab:containers.container.requirements]]), except that the
-`size()` member function is not provided and `operator==` has linear
-complexity. A `forward_list` also satisfies all of the requirements for
-an allocator-aware container (Table  [[tab:containers.allocatoraware]]).
-In addition, a `forward_list` provides the `assign` member functions
-(Table  [[tab:containers.sequence.requirements]]) and several of the
-optional container requirements (Table
-[[tab:containers.sequence.optional]]). Descriptions are provided here
-only for operations on `forward_list` that are not described in that
-table or for operations where there is additional semantic information.
 [*Note 2*: Modifying any list requires access to the element preceding
 the first element of interest, but in a `forward_list` there is no
 constant-time way to access a preceding element. For this reason, ranges
 that are modified, such as those supplied to `erase` and `splice`, must
@@ -1695,11 +1781,11 @@ be open at the beginning. — *end note*]
 ``` cpp
 namespace std {
   template<class T, class Allocator = allocator<T>>
   class forward_list {
   public:
-    // types:
     using value_type      = T;
     using allocator_type  = Allocator;
     using pointer         = typename allocator_traits<Allocator>::pointer;
     using const_pointer   = typename allocator_traits<Allocator>::const_pointer;
     using reference       = value_type&;
@@ -1711,15 +1797,13 @@ namespace std {
     // [forwardlist.cons], construct/copy/destroy
     forward_list() : forward_list(Allocator()) { }
     explicit forward_list(const Allocator&);
     explicit forward_list(size_type n, const Allocator& = Allocator());
-    forward_list(size_type n, const T& value,
-                 const Allocator& = Allocator());
     template<class InputIterator>
-      forward_list(InputIterator first, InputIterator last,
-                   const Allocator& = Allocator());
     forward_list(const forward_list& x);
     forward_list(forward_list&& x);
     forward_list(const forward_list& x, const Allocator&);
     forward_list(forward_list&& x, const Allocator&);
     forward_list(initializer_list<T>, const Allocator& = Allocator());
@@ -1744,12 +1828,12 @@ namespace std {
     const_iterator cbegin() const noexcept;
     const_iterator cbefore_begin() const noexcept;
     const_iterator cend() const noexcept;
-    // capacity:
-    bool empty() const noexcept;
     size_type max_size() const noexcept;
     // [forwardlist.access], element access
     reference front();
     const_reference front() const;
@@ -1779,24 +1863,22 @@ namespace std {
     void clear() noexcept;
     // [forwardlist.ops], forward_list operations
     void splice_after(const_iterator position, forward_list& x);
     void splice_after(const_iterator position, forward_list&& x);
-    void splice_after(const_iterator position, forward_list& x,
- const_iterator i);
-    void splice_after(const_iterator position, forward_list&& x,
-                      const_iterator i);
     void splice_after(const_iterator position, forward_list& x,
                       const_iterator first, const_iterator last);
     void splice_after(const_iterator position, forward_list&& x,
                       const_iterator first, const_iterator last);
- void remove(const T& value);
-    template <class Predicate> void remove_if(Predicate pred);
- void unique();
-    template <class BinaryPredicate> void unique(BinaryPredicate binary_pred);
     void merge(forward_list& x);
     void merge(forward_list&& x);
     template<class Compare> void merge(forward_list& x, Compare comp);
     template<class Compare> void merge(forward_list&& x, Compare comp);
@@ -1805,42 +1887,28 @@ namespace std {
     template<class Compare> void sort(Compare comp);
     void reverse() noexcept;
   };
-  template<class InputIterator,
-           class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
     forward_list(InputIterator, InputIterator, Allocator = Allocator())
-      -> forward_list<typename iterator_traits<InputIterator>::value_type, Allocator>;
- template <class T, class Allocator>
-    bool operator==(const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator< (const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator!=(const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator> (const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator>=(const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator<=(const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
-  // [forwardlist.spec], specialized algorithms
   template<class T, class Allocator>
     void swap(forward_list<T, Allocator>& x, forward_list<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
 An incomplete type `T` may be used when instantiating `forward_list` if
-the allocator satisfies the allocator completeness requirements (
-[[allocator.requirements.completeness]]). `T` shall be complete before
 any member of the resulting specialization of `forward_list` is
 referenced.
-#### `forward_list` constructors, copy, assignment <a id="forwardlist.cons">[[forwardlist.cons]]</a>
 ``` cpp
 explicit forward_list(const Allocator&);
 ```
@@ -1851,26 +1919,26 @@ allocator.
 ``` cpp
 explicit forward_list(size_type n, const Allocator& = Allocator());
 ```
 *Effects:* Constructs a `forward_list` object with `n` default-inserted
 elements using the specified allocator.
-*Requires:* `T` shall be `DefaultInsertable` into `*this`.
 *Complexity:* Linear in `n`.
 ``` cpp
 forward_list(size_type n, const T& value, const Allocator& = Allocator());
 ```
 *Effects:* Constructs a `forward_list` object with `n` copies of `value`
 using the specified allocator.
-*Requires:* `T` shall be `CopyInsertable` into `*this`.
 *Complexity:* Linear in `n`.
 ``` cpp
 template<class InputIterator>
   forward_list(InputIterator first, InputIterator last, const Allocator& = Allocator());
@@ -1879,11 +1947,11 @@ template <class InputIterator>
 *Effects:* Constructs a `forward_list` object equal to the range
 \[`first`, `last`).
 *Complexity:* Linear in `distance(first, last)`.
-#### `forward_list` iterators <a id="forwardlist.iter">[[forwardlist.iter]]</a>
 ``` cpp
 iterator before_begin() noexcept;
 const_iterator before_begin() const noexcept;
 const_iterator cbefore_begin() const noexcept;
@@ -1895,20 +1963,20 @@ equal to the iterator returned by `begin()`.
 *Effects:* `cbefore_begin()` is equivalent to
 `const_cast<forward_list const&>(*this).before_begin()`.
 *Remarks:* `before_begin() == end()` shall equal `false`.
-#### `forward_list` element access <a id="forwardlist.access">[[forwardlist.access]]</a>
 ``` cpp
 reference front();
 const_reference front() const;
 ```
 *Returns:* `*begin()`
-#### `forward_list` modifiers <a id="forwardlist.modifiers">[[forwardlist.modifiers]]</a>
 None of the overloads of `insert_after` shall affect the validity of
 iterators and references, and `erase_after` shall invalidate only
 iterators and references to the erased elements. If an exception is
 thrown during `insert_after` there shall be no effect. Inserting `n`
@@ -1940,22 +2008,22 @@ void pop_front();
 ``` cpp
 iterator insert_after(const_iterator position, const T& x);
 iterator insert_after(const_iterator position, T&& x);
 ```
-*Requires:* `position` is `before_begin()` or is a dereferenceable
 iterator in the range \[`begin()`, `end()`).
 *Effects:* Inserts a copy of `x` after `position`.
 *Returns:* An iterator pointing to the copy of `x`.
 ``` cpp
 iterator insert_after(const_iterator position, size_type n, const T& x);
 ```
-*Requires:* `position` is `before_begin()` or is a dereferenceable
 iterator in the range \[`begin()`, `end()`).
 *Effects:* Inserts `n` copies of `x` after `position`.
 *Returns:* An iterator pointing to the last inserted copy of `x` or
@@ -1964,13 +2032,13 @@ iterator in the range \[`begin()`, `end()`).
 ``` cpp
 template<class InputIterator>
   iterator insert_after(const_iterator position, InputIterator first, InputIterator last);
 ```
-*Requires:* `position` is `before_begin()` or is a dereferenceable
-iterator in the range \[`begin()`, `end()`). `first` and `last` are not
-iterators in `*this`.
 *Effects:* Inserts copies of elements in \[`first`, `last`) after
 `position`.
 *Returns:* An iterator pointing to the last inserted element or
@@ -1988,11 +2056,11 @@ iterator insert_after(const_iterator position, initializer_list<T> il);
 ``` cpp
 template<class... Args>
   iterator emplace_after(const_iterator position, Args&&... args);
 ```
-*Requires:* `position` is `before_begin()` or is a dereferenceable
 iterator in the range \[`begin()`, `end()`).
 *Effects:* Inserts an object of type `value_type` constructed with
 `value_type(std::forward<Args>(args)...)` after `position`.
@@ -2000,11 +2068,11 @@ iterator in the range \[`begin()`, `end()`).
 ``` cpp
 iterator erase_after(const_iterator position);
 ```
-*Requires:* The iterator following `position` is dereferenceable.
 *Effects:* Erases the element pointed to by the iterator following
 `position`.
 *Returns:* An iterator pointing to the element following the one that
@@ -2014,11 +2082,11 @@ was erased, or `end()` if no such element exists.
 ``` cpp
 iterator erase_after(const_iterator position, const_iterator last);
 ```
-*Requires:* All iterators in the range (`position`, `last`) are
 dereferenceable.
 *Effects:* Erases the elements in the range (`position`, `last`).
 *Returns:* `last`.
@@ -2027,46 +2095,52 @@ dereferenceable.
 ``` cpp
 void resize(size_type sz);
 ```
 *Effects:* If `sz < distance(begin(), end())`, erases the last
 `distance(begin(), end()) - sz` elements from the list. Otherwise,
 inserts `sz - distance(begin(), end())` default-inserted elements at the
 end of the list.
-*Requires:* `T` shall be `DefaultInsertable` into `*this`.
 ``` cpp
 void resize(size_type sz, const value_type& c);
 ```
 *Effects:* If `sz < distance(begin(), end())`, erases the last
 `distance(begin(), end()) - sz` elements from the list. Otherwise,
 inserts `sz - distance(begin(), end())` copies of `c` at the end of the
 list.
-*Requires:* `T` shall be `CopyInsertable` into `*this`.
 ``` cpp
 void clear() noexcept;
 ```
 *Effects:* Erases all elements in the range \[`begin()`, `end()`).
 *Remarks:* Does not invalidate past-the-end iterators.
-#### `forward_list` operations <a id="forwardlist.ops">[[forwardlist.ops]]</a>
 ``` cpp
 void splice_after(const_iterator position, forward_list& x);
 void splice_after(const_iterator position, forward_list&& x);
 ```
-*Requires:* `position` is `before_begin()` or is a dereferenceable
 iterator in the range \[`begin()`, `end()`).
-`get_allocator() == x.get_allocator()`. `&x != this`.
 *Effects:* Inserts the contents of `x` after `position`, and `x` becomes
 empty. Pointers and references to the moved elements of `x` now refer to
 those same elements but as members of `*this`. Iterators referring to
 the moved elements will continue to refer to their elements, but they
@@ -2079,14 +2153,14 @@ now behave as iterators into `*this`, not into `x`.
 ``` cpp
 void splice_after(const_iterator position, forward_list& x, const_iterator i);
 void splice_after(const_iterator position, forward_list&& x, const_iterator i);
 ```
-*Requires:* `position` is `before_begin()` or is a dereferenceable
 iterator in the range \[`begin()`, `end()`). The iterator following `i`
 is a dereferenceable iterator in `x`.
-`get_allocator() == x.get_allocator()`.
 *Effects:* Inserts the element following `i` into `*this`, following
 `position`, and removes it from `x`. The result is unchanged if
 `position == i` or `position == ++i`. Pointers and references to `*++i`
 continue to refer to the same element but as a member of `*this`.
@@ -2102,15 +2176,15 @@ void splice_after(const_iterator position, forward_list& x,
                   const_iterator first, const_iterator last);
 void splice_after(const_iterator position, forward_list&& x,
                   const_iterator first, const_iterator last);
 ```
-*Requires:* `position` is `before_begin()` or is a dereferenceable
 iterator in the range \[`begin()`, `end()`). (`first`, `last`) is a
 valid range in `x`, and all iterators in the range (`first`, `last`) are
 dereferenceable. `position` is not an iterator in the range (`first`,
-`last`). `get_allocator() == x.get_allocator()`.
 *Effects:* Inserts elements in the range (`first`, `last`) after
 `position` and removes the elements from `x`. Pointers and references to
 the moved elements of `x` now refer to those same elements but as
 members of `*this`. Iterators referring to the moved elements will
@@ -2118,39 +2192,43 @@ continue to refer to their elements, but they now behave as iterators
 into `*this`, not into `x`.
 *Complexity:* 𝑂(`distance(first, last)`)
 ``` cpp
-void remove(const T& value);
-template <class Predicate> void remove_if(Predicate pred);
 ```
-*Effects:* Erases all the elements in the list referred by a list
 iterator `i` for which the following conditions hold: `*i == value` (for
 `remove()`), `pred(*i)` is `true` (for `remove_if()`). Invalidates only
 the iterators and references to the erased elements.
 *Throws:* Nothing unless an exception is thrown by the equality
 comparison or the predicate.
-*Remarks:* Stable ([[algorithm.stable]]).
 *Complexity:* Exactly `distance(begin(), end())` applications of the
 corresponding predicate.
 ``` cpp
-void unique();
-template <class BinaryPredicate> void unique(BinaryPredicate pred);
 ```
 *Effects:* Erases all but the first element from every consecutive group
 of equal elements referred to by the iterator `i` in the range
 \[`first + 1`, `last`) for which `*i == *(i-1)` (for the version with no
 arguments) or `pred(*i, *(i - 1))` (for the version with a predicate
 argument) holds. Invalidates only the iterators and references to the
 erased elements.
 *Throws:* Nothing unless an exception is thrown by the equality
 comparison or the predicate.
 *Complexity:* If the range \[`first`, `last`) is not empty, exactly
 `(last - first) - 1` applications of the corresponding predicate,
@@ -2161,44 +2239,40 @@ void merge(forward_list& x);
 void merge(forward_list&& x);
 template<class Compare> void merge(forward_list& x, Compare comp);
 template<class Compare> void merge(forward_list&& x, Compare comp);
 ```
-*Requires:* `comp` defines a strict weak ordering ([[alg.sorting]]),
-and `*this` and `x` are both sorted according to this ordering.
-`get_allocator() == x.get_allocator()`.
 *Effects:* Merges the two sorted ranges `[begin(), end())` and
 `[x.begin(), x.end())`. `x` is empty after the merge. If an exception is
 thrown other than by a comparison there are no effects. Pointers and
 references to the moved elements of `x` now refer to those same elements
 but as members of `*this`. Iterators referring to the moved elements
 will continue to refer to their elements, but they now behave as
 iterators into `*this`, not into `x`.
-*Remarks:* Stable ([[algorithm.stable]]). The behavior is undefined if
-`get_allocator() != x.get_allocator()`.
 *Complexity:* At most
 `distance(begin(), end()) + distance(x.begin(), x.end()) - 1`
 comparisons.
 ``` cpp
 void sort();
 template<class Compare> void sort(Compare comp);
 ```
-*Requires:* `operator<` (for the version with no arguments) or `comp`
-(for the version with a comparison argument) defines a strict weak
-ordering ([[alg.sorting]]).
 *Effects:* Sorts the list according to the `operator<` or the `comp`
 function object. If an exception is thrown, the order of the elements in
 `*this` is unspecified. Does not affect the validity of iterators and
 references.
-*Remarks:* Stable ([[algorithm.stable]]).
 *Complexity:* Approximately N log N comparisons, where N is
 `distance(begin(), end())`.
 ``` cpp
@@ -2208,48 +2282,55 @@ void reverse() noexcept;
 *Effects:* Reverses the order of the elements in the list. Does not
 affect the validity of iterators and references.
 *Complexity:* Linear time.
-#### `forward_list` specialized algorithms <a id="forwardlist.spec">[[forwardlist.spec]]</a>
 ``` cpp
-template <class T, class Allocator>
- void swap(forward_list<T, Allocator>& x, forward_list<T, Allocator>& y)
- noexcept(noexcept(x.swap(y)));
 ```
-*Effects:* As if by `x.swap(y)`.
 ### Class template `list` <a id="list">[[list]]</a>
-#### Class template `list` overview <a id="list.overview">[[list.overview]]</a>
 A `list` is a sequence container that supports bidirectional iterators
 and allows constant time insert and erase operations anywhere within the
-sequence, with storage management handled automatically. Unlike
-vectors ([[vector]]) and deques ([[deque]]), fast random access to
-list elements is not supported, but many algorithms only need sequential
-access anyway.
-A `list` satisfies all of the requirements of a container, of a
-reversible container (given in two tables in
-[[container.requirements]]), of a sequence container, including most of
-the optional sequence container requirements ([[sequence.reqmts]]), and
-of an allocator-aware container (Table
-[[tab:containers.allocatoraware]]). The exceptions are the `operator[]`
-and `at` member functions, which are not provided.[^2] Descriptions are
-provided here only for operations on `list` that are not described in
-one of these tables or for operations where there is additional semantic
 information.
 ``` cpp
 namespace std {
   template<class T, class Allocator = allocator<T>>
   class list {
   public:
-    // types:
     using value_type             = T;
     using allocator_type         = Allocator;
     using pointer                = typename allocator_traits<Allocator>::pointer;
     using const_pointer          = typename allocator_traits<Allocator>::const_pointer;
     using reference              = value_type&;
@@ -2282,11 +2363,11 @@ namespace std {
       void assign(InputIterator first, InputIterator last);
     void assign(size_type n, const T& t);
     void assign(initializer_list<T>);
     allocator_type get_allocator() const noexcept;
-    // iterators:
     iterator               begin() noexcept;
     const_iterator         begin() const noexcept;
     iterator               end() noexcept;
     const_iterator         end() const noexcept;
     reverse_iterator       rbegin() noexcept;
@@ -2298,17 +2379,17 @@ namespace std {
     const_iterator         cend() const noexcept;
     const_reverse_iterator crbegin() const noexcept;
     const_reverse_iterator crend() const noexcept;
     // [list.capacity], capacity
-    bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
     void      resize(size_type sz);
     void      resize(size_type sz, const T& c);
-    // element access:
     reference       front();
     const_reference front() const;
     reference       back();
     const_reference back() const;
@@ -2325,36 +2406,32 @@ namespace std {
     template<class... Args> iterator emplace(const_iterator position, Args&&... args);
     iterator insert(const_iterator position, const T& x);
     iterator insert(const_iterator position, T&& x);
     iterator insert(const_iterator position, size_type n, const T& x);
     template<class InputIterator>
-      iterator insert(const_iterator position, InputIterator first,
-                      InputIterator last);
     iterator insert(const_iterator position, initializer_list<T> il);
     iterator erase(const_iterator position);
     iterator erase(const_iterator position, const_iterator last);
-    void     swap(list&)
-      noexcept(allocator_traits<Allocator>::is_always_equal::value);
     void     clear() noexcept;
     // [list.ops], list operations
     void splice(const_iterator position, list& x);
     void splice(const_iterator position, list&& x);
     void splice(const_iterator position, list& x, const_iterator i);
     void splice(const_iterator position, list&& x, const_iterator i);
-    void splice(const_iterator position, list& x,
- const_iterator first, const_iterator last);
-    void splice(const_iterator position, list&& x,
-                const_iterator first, const_iterator last);
- void remove(const T& value);
-    template <class Predicate> void remove_if(Predicate pred);
- void unique();
     template<class BinaryPredicate>
- void unique(BinaryPredicate binary_pred);
     void merge(list& x);
     void merge(list&& x);
     template<class Compare> void merge(list& x, Compare comp);
     template<class Compare> void merge(list&& x, Compare comp);
@@ -2363,41 +2440,27 @@ namespace std {
     template<class Compare> void sort(Compare comp);
     void reverse() noexcept;
   };
-  template<class InputIterator,
-           class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
     list(InputIterator, InputIterator, Allocator = Allocator())
-      -> list<typename iterator_traits<InputIterator>::value_type, Allocator>;
- template <class T, class Allocator>
-    bool operator==(const list<T, Allocator>& x, const list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator< (const list<T, Allocator>& x, const list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator!=(const list<T, Allocator>& x, const list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator> (const list<T, Allocator>& x, const list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator>=(const list<T, Allocator>& x, const list<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator<=(const list<T, Allocator>& x, const list<T, Allocator>& y);
-  // [list.special], specialized algorithms
   template<class T, class Allocator>
     void swap(list<T, Allocator>& x, list<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
 An incomplete type `T` may be used when instantiating `list` if the
-allocator satisfies the allocator completeness requirements (
-[[allocator.requirements.completeness]]). `T` shall be complete before
 any member of the resulting specialization of `list` is referenced.
-#### `list` constructors, copy, and assignment <a id="list.cons">[[list.cons]]</a>
 ``` cpp
 explicit list(const Allocator&);
 ```
@@ -2407,26 +2470,26 @@ explicit list(const Allocator&);
 ``` cpp
 explicit list(size_type n, const Allocator& = Allocator());
 ```
 *Effects:* Constructs a `list` with `n` default-inserted elements using
 the specified allocator.
-*Requires:* `T` shall be `DefaultInsertable` into `*this`.
 *Complexity:* Linear in `n`.
 ``` cpp
 list(size_type n, const T& value, const Allocator& = Allocator());
 ```
 *Effects:* Constructs a `list` with `n` copies of `value`, using the
 specified allocator.
-*Requires:* `T` shall be `CopyInsertable` into `*this`.
 *Complexity:* Linear in `n`.
 ``` cpp
 template<class InputIterator>
   list(InputIterator first, InputIterator last, const Allocator& = Allocator());
@@ -2434,31 +2497,33 @@ template <class InputIterator>
 *Effects:* Constructs a `list` equal to the range \[`first`, `last`).
 *Complexity:* Linear in `distance(first, last)`.
-#### `list` capacity <a id="list.capacity">[[list.capacity]]</a>
 ``` cpp
 void resize(size_type sz);
 ```
 *Effects:* If `size() < sz`, appends `sz - size()` default-inserted
 elements to the sequence. If `sz <= size()`, equivalent to:
 ``` cpp
 list<T>::iterator it = begin();
 advance(it, sz);
 erase(it, end());
 ```
-*Requires:* `T` shall be `DefaultInsertable` into `*this`.
 ``` cpp
 void resize(size_type sz, const T& c);
 ```
 *Effects:* As if by:
 ``` cpp
 if (sz > size())
   insert(end(), sz-size(), c);
@@ -2469,13 +2534,11 @@ else if (sz < size()) {
 }
 else
   ;                 // do nothing
 ```
-*Requires:* `T` shall be `CopyInsertable` into `*this`.
-#### `list` modifiers <a id="list.modifiers">[[list.modifiers]]</a>
 ``` cpp
 iterator insert(const_iterator position, const T& x);
 iterator insert(const_iterator position, T&& x);
 iterator insert(const_iterator position, size_type n, const T& x);
@@ -2519,14 +2582,18 @@ elements.
 *Complexity:* Erasing a single element is a constant time operation with
 a single call to the destructor of `T`. Erasing a range in a list is
 linear time in the size of the range and the number of calls to the
 destructor of type `T` is exactly equal to the size of the range.
-#### `list` operations <a id="list.ops">[[list.ops]]</a>
 Since lists allow fast insertion and erasing from the middle of a list,
-certain operations are provided specifically for them.[^3]
 `list` provides three splice operations that destructively move elements
 from one list to another. The behavior of splice operations is undefined
 if `get_allocator() !=
 x.get_allocator()`.
@@ -2534,11 +2601,11 @@ x.get_allocator()`.
 ``` cpp
 void splice(const_iterator position, list& x);
 void splice(const_iterator position, list&& x);
 ```
-*Requires:* `&x != this`.
 *Effects:* Inserts the contents of `x` before `position` and `x` becomes
 empty. Pointers and references to the moved elements of `x` now refer to
 those same elements but as members of `*this`. Iterators referring to
 the moved elements will continue to refer to their elements, but they
@@ -2551,11 +2618,11 @@ now behave as iterators into `*this`, not into `x`.
 ``` cpp
 void splice(const_iterator position, list& x, const_iterator i);
 void splice(const_iterator position, list&& x, const_iterator i);
 ```
-*Requires:* `i` is a valid dereferenceable iterator of `x`.
 *Effects:* Inserts an element pointed to by `i` from list `x` before
 `position` and removes the element from `x`. The result is unchanged if
 `position == i` or `position == ++i`. Pointers and references to `*i`
 continue to refer to this same element but as a member of `*this`.
@@ -2571,55 +2638,59 @@ void splice(const_iterator position, list& x, const_iterator first,
             const_iterator last);
 void splice(const_iterator position, list&& x, const_iterator first,
             const_iterator last);
 ```
-*Requires:* `[first, last)` is a valid range in `x`. The program has
-undefined behavior if `position` is an iterator in the range \[`first`,
-`last`).
 *Effects:* Inserts elements in the range \[`first`, `last`) before
 `position` and removes the elements from `x`. Pointers and references to
 the moved elements of `x` now refer to those same elements but as
 members of `*this`. Iterators referring to the moved elements will
 continue to refer to their elements, but they now behave as iterators
 into `*this`, not into `x`.
 *Throws:* Nothing.
-*Complexity:* Constant time if `&x == this`; otherwise, linear time.
 ``` cpp
-void remove(const T& value);
-template <class Predicate> void remove_if(Predicate pred);
 ```
-*Effects:* Erases all the elements in the list referred by a list
-iterator `i` for which the following conditions hold:
-`*i == value, pred(*i) != false`. Invalidates only the iterators and
-references to the erased elements.
 *Throws:* Nothing unless an exception is thrown by `*i == value` or
 `pred(*i) != false`.
-*Remarks:* Stable ([[algorithm.stable]]).
 *Complexity:* Exactly `size()` applications of the corresponding
 predicate.
 ``` cpp
-void unique();
-template <class BinaryPredicate> void unique(BinaryPredicate binary_pred);
 ```
 *Effects:* Erases all but the first element from every consecutive group
 of equal elements referred to by the iterator `i` in the range
 \[`first + 1`, `last`) for which `*i == *(i-1)` (for the version of
 `unique` with no arguments) or `pred(*i, *(i - 1))` (for the version of
 `unique` with a predicate argument) holds. Invalidates only the
 iterators and references to the erased elements.
 *Throws:* Nothing unless an exception is thrown by `*i == *(i-1)` or
 `pred(*i, *(i - 1))`
 *Complexity:* If the range `[first, last)` is not empty, exactly
 `(last - first) - 1` applications of the corresponding predicate,
@@ -2630,33 +2701,34 @@ void merge(list& x);
 void merge(list&& x);
 template<class Compare> void merge(list& x, Compare comp);
 template<class Compare> void merge(list&& x, Compare comp);
 ```
-*Requires:* `comp` shall define a strict weak
-ordering ([[alg.sorting]]), and both the list and the argument list
-shall be sorted according to this ordering.
-*Effects:* If `(&x == this)` does nothing; otherwise, merges the two
-sorted ranges `[begin(), end())` and `[x.begin(), x.end())`. The result
-is a range in which the elements will be sorted in non-decreasing order
-according to the ordering defined by `comp`; that is, for every iterator
-`i`, in the range other than the first, the condition
 `comp(*i, *(i - 1))` will be `false`. Pointers and references to the
 moved elements of `x` now refer to those same elements but as members of
 `*this`. Iterators referring to the moved elements will continue to
 refer to their elements, but they now behave as iterators into `*this`,
 not into `x`.
-*Remarks:* Stable ([[algorithm.stable]]). If `(&x != this)` the range
-`[x.begin(), x.end())` is empty after the merge. No elements are copied
-by this operation. The behavior is undefined if
-`get_allocator() != x.get_allocator()`.
 *Complexity:* At most `size() + x.size() - 1` applications of `comp` if
-`(&x != this)`; otherwise, no applications of `comp` are performed. If
-an exception is thrown other than by a comparison there are no effects.
 ``` cpp
 void reverse() noexcept;
 ```
@@ -2668,59 +2740,68 @@ affect the validity of iterators and references.
 ``` cpp
 void sort();
 template<class Compare> void sort(Compare comp);
 ```
-*Requires:* `operator<` (for the first version) or `comp` (for the
-second version) shall define a strict weak ordering ([[alg.sorting]]).
 *Effects:* Sorts the list according to the `operator<` or a `Compare`
 function object. If an exception is thrown, the order of the elements in
 `*this` is unspecified. Does not affect the validity of iterators and
 references.
-*Remarks:* Stable ([[algorithm.stable]]).
 *Complexity:* Approximately N log N comparisons, where `N == size()`.
-#### `list` specialized algorithms <a id="list.special">[[list.special]]</a>
 ``` cpp
-template <class T, class Allocator>
- void swap(list<T, Allocator>& x, list<T, Allocator>& y)
- noexcept(noexcept(x.swap(y)));
 ```
-*Effects:* As if by `x.swap(y)`.
 ### Class template `vector` <a id="vector">[[vector]]</a>
-#### Class template `vector` overview <a id="vector.overview">[[vector.overview]]</a>
 A `vector` is a sequence container that supports (amortized) constant
 time insert and erase operations at the end; insert and erase in the
 middle take linear time. Storage management is handled automatically,
 though hints can be given to improve efficiency.
-A `vector` satisfies all of the requirements of a container and of a
 reversible container (given in two tables in
 [[container.requirements]]), of a sequence container, including most of
-the optional sequence container requirements ([[sequence.reqmts]]), of
-an allocator-aware container (Table  [[tab:containers.allocatoraware]]),
-and, for an element type other than `bool`, of a contiguous container (
-[[container.requirements.general]]). The exceptions are the
-`push_front`, `pop_front`, and `emplace_front` member functions, which
-are not provided. Descriptions are provided here only for operations on
-`vector` that are not described in one of these tables or for operations
-where there is additional semantic information.
 ``` cpp
 namespace std {
   template<class T, class Allocator = allocator<T>>
   class vector {
   public:
-    // types:
     using value_type             = T;
     using allocator_type         = Allocator;
     using pointer                = typename allocator_traits<Allocator>::pointer;
     using const_pointer          = typename allocator_traits<Allocator>::const_pointer;
     using reference              = value_type&;
@@ -2731,159 +2812,146 @@ namespace std {
     using const_iterator         = implementation-defined  // type of vector::const_iterator; // see [container.requirements]
     using reverse_iterator       = std::reverse_iterator<iterator>;
     using const_reverse_iterator = std::reverse_iterator<const_iterator>;
     // [vector.cons], construct/copy/destroy
-    vector() noexcept(noexcept(Allocator())) : vector(Allocator()) { }
-    explicit vector(const Allocator&) noexcept;
-    explicit vector(size_type n, const Allocator& = Allocator());
-    vector(size_type n, const T& value, const Allocator& = Allocator());
     template<class InputIterator>
-      vector(InputIterator first, InputIterator last, const Allocator& = Allocator());
-    vector(const vector& x);
-    vector(vector&&) noexcept;
-    vector(const vector&, const Allocator&);
-    vector(vector&&, const Allocator&);
-    vector(initializer_list<T>, const Allocator& = Allocator());
-    ~vector();
-    vector& operator=(const vector& x);
-    vector& operator=(vector&& x)
       noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value ||
                allocator_traits<Allocator>::is_always_equal::value);
-    vector& operator=(initializer_list<T>);
     template<class InputIterator>
-      void assign(InputIterator first, InputIterator last);
-    void assign(size_type n, const T& u);
-    void assign(initializer_list<T>);
-    allocator_type get_allocator() const noexcept;
-    // iterators:
-    iterator               begin() noexcept;
-    const_iterator         begin() const noexcept;
-    iterator               end() noexcept;
-    const_iterator         end() const noexcept;
-    reverse_iterator       rbegin() noexcept;
-    const_reverse_iterator rbegin() const noexcept;
-    reverse_iterator       rend() noexcept;
-    const_reverse_iterator rend() const noexcept;
-    const_iterator         cbegin() const noexcept;
-    const_iterator         cend() const noexcept;
-    const_reverse_iterator crbegin() const noexcept;
-    const_reverse_iterator crend() const noexcept;
     // [vector.capacity], capacity
-    bool empty() const noexcept;
-    size_type size() const noexcept;
-    size_type max_size() const noexcept;
-    size_type capacity() const noexcept;
-    void      resize(size_type sz);
-    void      resize(size_type sz, const T& c);
-    void      reserve(size_type n);
-    void      shrink_to_fit();
-    // element access:
-    reference       operator[](size_type n);
-    const_reference operator[](size_type n) const;
-    const_reference at(size_type n) const;
-    reference       at(size_type n);
-    reference       front();
-    const_reference front() const;
-    reference       back();
-    const_reference back() const;
     // [vector.data], data access
-    T*       data() noexcept;
-    const T* data() const noexcept;
     // [vector.modifiers], modifiers
-    template <class... Args> reference emplace_back(Args&&... args);
-    void push_back(const T& x);
-    void push_back(T&& x);
-    void pop_back();
-    template <class... Args> iterator emplace(const_iterator position, Args&&... args);
-    iterator insert(const_iterator position, const T& x);
-    iterator insert(const_iterator position, T&& x);
-    iterator insert(const_iterator position, size_type n, const T& x);
     template<class InputIterator>
-      iterator insert(const_iterator position, InputIterator first, InputIterator last);
-    iterator insert(const_iterator position, initializer_list<T> il);
-    iterator erase(const_iterator position);
-    iterator erase(const_iterator first, const_iterator last);
- void     swap(vector&)
       noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value ||
                allocator_traits<Allocator>::is_always_equal::value);
-    void     clear() noexcept;
   };
-  template<class InputIterator,
-           class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
     vector(InputIterator, InputIterator, Allocator = Allocator())
-      -> vector<typename iterator_traits<InputIterator>::value_type, Allocator>;
   template<class T, class Allocator>
- bool operator==(const vector<T, Allocator>& x, const vector<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator< (const vector<T, Allocator>& x, const vector<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator!=(const vector<T, Allocator>& x, const vector<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator> (const vector<T, Allocator>& x, const vector<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator>=(const vector<T, Allocator>& x, const vector<T, Allocator>& y);
-  template <class T, class Allocator>
-    bool operator<=(const vector<T, Allocator>& x, const vector<T, Allocator>& y);
-  // [vector.special], specialized algorithms
-  template <class T, class Allocator>
-    void swap(vector<T, Allocator>& x, vector<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
 An incomplete type `T` may be used when instantiating `vector` if the
-allocator satisfies the allocator completeness requirements (
-[[allocator.requirements.completeness]]). `T` shall be complete before
 any member of the resulting specialization of `vector` is referenced.
-#### `vector` constructors, copy, and assignment <a id="vector.cons">[[vector.cons]]</a>
 ``` cpp
-explicit vector(const Allocator&);
 ```
 *Effects:* Constructs an empty `vector`, using the specified allocator.
 *Complexity:* Constant.
 ``` cpp
-explicit vector(size_type n, const Allocator& = Allocator());
 ```
 *Effects:* Constructs a `vector` with `n` default-inserted elements
 using the specified allocator.
-*Requires:* `T` shall be `DefaultInsertable` into `*this`.
 *Complexity:* Linear in `n`.
 ``` cpp
-vector(size_type n, const T& value,
                  const Allocator& = Allocator());
 ```
 *Effects:* Constructs a `vector` with `n` copies of `value`, using the
 specified allocator.
-*Requires:* `T` shall be `CopyInsertable` into `*this`.
 *Complexity:* Linear in `n`.
 ``` cpp
 template<class InputIterator>
-  vector(InputIterator first, InputIterator last,
                    const Allocator& = Allocator());
 ```
 *Effects:* Constructs a `vector` equal to the range \[`first`, `last`),
 using the specified allocator.
@@ -2892,152 +2960,166 @@ using the specified allocator.
 is the distance between `first` and `last`) and no reallocations if
 iterators `first` and `last` are of forward, bidirectional, or random
 access categories. It makes order `N` calls to the copy constructor of
 `T` and order log N reallocations if they are just input iterators.
-#### `vector` capacity <a id="vector.capacity">[[vector.capacity]]</a>
 ``` cpp
-size_type capacity() const noexcept;
 ```
 *Returns:* The total number of elements that the vector can hold without
 requiring reallocation.
 ``` cpp
-void reserve(size_type n);
 ```
-*Requires:* `T` shall be `MoveInsertable` into `*this`.
 *Effects:* A directive that informs a `vector` of a planned change in
 size, so that it can manage the storage allocation accordingly. After
 `reserve()`, `capacity()` is greater or equal to the argument of
 `reserve` if reallocation happens; and equal to the previous value of
 `capacity()` otherwise. Reallocation happens at this point if and only
 if the current capacity is less than the argument of `reserve()`. If an
 exception is thrown other than by the move constructor of a
-non-`CopyInsertable` type, there are no effects.
 *Complexity:* It does not change the size of the sequence and takes at
 most linear time in the size of the sequence.
 *Throws:* `length_error` if `n > max_size()`.[^4]
 *Remarks:* Reallocation invalidates all the references, pointers, and
-iterators referring to the elements in the sequence. No reallocation
-shall take place during insertions that happen after a call to
-`reserve()` until the time when an insertion would make the size of the
-vector greater than the value of `capacity()`.
 ``` cpp
-void shrink_to_fit();
 ```
-*Requires:* `T` shall be `MoveInsertable` into `*this`.
 *Effects:* `shrink_to_fit` is a non-binding request to reduce
 `capacity()` to `size()`.
-[*Note 1*: The request is non-binding to allow latitude for
 implementation-specific optimizations. — *end note*]
 It does not increase `capacity()`, but may reduce `capacity()` by
 causing reallocation. If an exception is thrown other than by the move
-constructor of a non-`CopyInsertable` `T` there are no effects.
-*Complexity:* Linear in the size of the sequence.
 *Remarks:* Reallocation invalidates all the references, pointers, and
 iterators referring to the elements in the sequence as well as the
-past-the-end iterator. If no reallocation happens, they remain valid.
 ``` cpp
-void swap(vector& x)
   noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value ||
            allocator_traits<Allocator>::is_always_equal::value);
 ```
 *Effects:* Exchanges the contents and `capacity()` of `*this` with that
 of `x`.
 *Complexity:* Constant time.
 ``` cpp
-void resize(size_type sz);
 ```
 *Effects:* If `sz < size()`, erases the last `size() - sz` elements from
 the sequence. Otherwise, appends `sz - size()` default-inserted elements
 to the sequence.
-*Requires:* `T` shall be `MoveInsertable` and `DefaultInsertable` into
-`*this`.
 *Remarks:* If an exception is thrown other than by the move constructor
-of a non-`CopyInsertable` `T` there are no effects.
 ``` cpp
-void resize(size_type sz, const T& c);
 ```
 *Effects:* If `sz < size()`, erases the last `size() - sz` elements from
 the sequence. Otherwise, appends `sz - size()` copies of `c` to the
 sequence.
-*Requires:* `T` shall be `CopyInsertable` into `*this`.
 *Remarks:* If an exception is thrown there are no effects.
-#### `vector` data <a id="vector.data">[[vector.data]]</a>
 ``` cpp
-T*         data() noexcept;
-const T*   data() const noexcept;
 ```
 *Returns:* A pointer such that \[`data()`, `data() + size()`) is a valid
 range. For a non-empty vector, `data()` `==` `addressof(front())`.
 *Complexity:* Constant time.
-#### `vector` modifiers <a id="vector.modifiers">[[vector.modifiers]]</a>
 ``` cpp
-iterator insert(const_iterator position, const T& x);
-iterator insert(const_iterator position, T&& x);
-iterator insert(const_iterator position, size_type n, const T& x);
 template<class InputIterator>
-  iterator insert(const_iterator position, InputIterator first, InputIterator last);
-iterator insert(const_iterator position, initializer_list<T>);
-template <class... Args> reference emplace_back(Args&&... args);
-template <class... Args> iterator emplace(const_iterator position, Args&&... args);
-void push_back(const T& x);
-void push_back(T&& x);
 ```
 *Remarks:* Causes reallocation if the new size is greater than the old
 capacity. Reallocation invalidates all the references, pointers, and
-iterators referring to the elements in the sequence. If no reallocation
-happens, all the iterators and references before the insertion point
-remain valid. If an exception is thrown other than by the copy
-constructor, move constructor, assignment operator, or move assignment
-operator of `T` or by any `InputIterator` operation there are no
-effects. If an exception is thrown while inserting a single element at
-the end and `T` is `CopyInsertable` or
 `is_nothrow_move_constructible_v<T>` is `true`, there are no effects.
 Otherwise, if an exception is thrown by the move constructor of a
-non-`CopyInsertable` `T`, the effects are unspecified.
-*Complexity:* The complexity is linear in the number of elements
 inserted plus the distance to the end of the vector.
 ``` cpp
-iterator erase(const_iterator position);
-iterator erase(const_iterator first, const_iterator last);
-void pop_back();
 ```
 *Effects:* Invalidates iterators and references at or after the point of
 the erase.
@@ -3047,19 +3129,41 @@ is called the number of times equal to the number of elements in the
 vector after the erased elements.
 *Throws:* Nothing unless an exception is thrown by the assignment
 operator or move assignment operator of `T`.
-#### `vector` specialized algorithms <a id="vector.special">[[vector.special]]</a>
 ``` cpp
-template <class T, class Allocator>
- void swap(vector<T, Allocator>& x, vector<T, Allocator>& y)
- noexcept(noexcept(x.swap(y)));
 ```
-*Effects:* As if by `x.swap(y)`.
 ### Class `vector<bool>` <a id="vector.bool">[[vector.bool]]</a>
 To optimize space allocation, a specialization of vector for `bool`
 elements is provided:
@@ -3067,11 +3171,11 @@ elements is provided:
 ``` cpp
 namespace std {
   template<class Allocator>
   class vector<bool, Allocator> {
   public:
-    // types:
     using value_type             = bool;
     using allocator_type         = Allocator;
     using pointer                = implementation-defined;
     using const_pointer          = implementation-defined;
     using const_reference        = bool;
@@ -3080,107 +3184,106 @@ namespace std {
     using iterator               = implementation-defined  // type of vector<bool>::iterator; // see [container.requirements]
     using const_iterator         = implementation-defined  // type of vector<bool>::const_iterator; // see [container.requirements]
     using reverse_iterator       = std::reverse_iterator<iterator>;
     using const_reverse_iterator = std::reverse_iterator<const_iterator>;
-    // bit reference:
     class reference {
       friend class vector;
-      reference() noexcept;
     public:
- ~reference();
- operator bool() const noexcept;
- reference& operator=(const bool x) noexcept;
-      reference& operator=(const reference& x) noexcept;
- void flip() noexcept;     // flips the bit
     };
-    // construct/copy/destroy:
-    vector() : vector(Allocator()) { }
-    explicit vector(const Allocator&);
-    explicit vector(size_type n, const Allocator& = Allocator());
-    vector(size_type n, const bool& value,
-           const Allocator& = Allocator());
     template<class InputIterator>
-      vector(InputIterator first, InputIterator last,
- const Allocator& = Allocator());
-    vector(const vector<bool, Allocator>& x);
-    vector(vector<bool, Allocator>&& x);
-    vector(const vector&, const Allocator&);
-    vector(vector&&, const Allocator&);
-    vector(initializer_list<bool>, const Allocator& = Allocator()));
- ~vector();
- vector<bool, Allocator>& operator=(const vector<bool, Allocator>& x);
- vector<bool, Allocator>& operator=(vector<bool, Allocator>&& x);
-    vector& operator=(initializer_list<bool>);
     template<class InputIterator>
-      void assign(InputIterator first, InputIterator last);
-    void assign(size_type n, const bool& t);
-    void assign(initializer_list<bool>);
-    allocator_type get_allocator() const noexcept;
-    // iterators:
-    iterator               begin() noexcept;
-    const_iterator         begin() const noexcept;
-    iterator               end() noexcept;
-    const_iterator         end() const noexcept;
-    reverse_iterator       rbegin() noexcept;
-    const_reverse_iterator rbegin() const noexcept;
-    reverse_iterator       rend() noexcept;
-    const_reverse_iterator rend() const noexcept;
-    const_iterator         cbegin() const noexcept;
-    const_iterator         cend() const noexcept;
-    const_reverse_iterator crbegin() const noexcept;
-    const_reverse_iterator crend() const noexcept;
-    // capacity:
-    bool empty() const noexcept;
-    size_type size() const noexcept;
-    size_type max_size() const noexcept;
-    size_type capacity() const noexcept;
-    void      resize(size_type sz, bool c = false);
-    void      reserve(size_type n);
-    void      shrink_to_fit();
-    // element access:
-    reference       operator[](size_type n);
-    const_reference operator[](size_type n) const;
-    const_reference at(size_type n) const;
-    reference       at(size_type n);
-    reference       front();
-    const_reference front() const;
-    reference       back();
-    const_reference back() const;
-    // modifiers:
-    template <class... Args> reference emplace_back(Args&&... args);
-    void push_back(const bool& x);
-    void pop_back();
-    template <class... Args> iterator emplace(const_iterator position, Args&&... args);
-    iterator insert(const_iterator position, const bool& x);
-    iterator insert(const_iterator position, size_type n, const bool& x);
     template<class InputIterator>
-      iterator insert(const_iterator position,
                                 InputIterator first, InputIterator last);
-    iterator insert(const_iterator position, initializer_list<bool> il);
-    iterator erase(const_iterator position);
-    iterator erase(const_iterator first, const_iterator last);
-    void swap(vector<bool, Allocator>&);
-    static void swap(reference x, reference y) noexcept;
-    void flip() noexcept; // flips all bits
-    void clear() noexcept;
   };
 }
 ```
 Unless described below, all operations have the same requirements and
 semantics as the primary `vector` template, except that operations
 dealing with the `bool` value type map to bit values in the container
-storage and `allocator_traits::construct` (
-[[allocator.traits.members]]) is not used to construct these values.
 There is no requirement that the data be stored as a contiguous
 allocation of `bool` values. A space-optimized representation of bits is
 recommended instead.
@@ -3191,17 +3294,17 @@ is a class that simulates the behavior of references of a single bit in
 set, and `false` otherwise. The assignment operator sets the bit when
 the argument is (convertible to) `true` and clears it otherwise. `flip`
 reverses the state of the bit.
 ``` cpp
-void flip() noexcept;
 ```
 *Effects:* Replaces each element in the container with its complement.
 ``` cpp
-static void swap(reference x, reference y) noexcept;
 ```
 *Effects:* Exchanges the contents of `x` and `y` as if by:
 ``` cpp
@@ -3212,11 +3315,11 @@ y = b;
 ``` cpp
 template<class Allocator> struct hash<vector<bool, Allocator>>;
 ```
-The specialization is enabled ([[unord.hash]]).
 ## Associative containers <a id="associative">[[associative]]</a>
 ### In general <a id="associative.general">[[associative.general]]</a>
@@ -3226,81 +3329,75 @@ header `<set>` defines the class templates `set` and `multiset`.
 The following exposition-only alias templates may appear in deduction
 guides for associative containers:
 ``` cpp
 template<class InputIterator>
-  using iter_key_t = remove_const_t<
     typename iterator_traits<InputIterator>::value_type::first_type>;   // exposition only
 template<class InputIterator>
-  using iter_val_t
- = typename iterator_traits<InputIterator>::value_type::second_type; // exposition only
 template<class InputIterator>
-  using iter_to_alloc_t
- = pair<add_const_t<typename iterator_traits<InputIterator>::value_type::first_type>,
     typename iterator_traits<InputIterator>::value_type::second_type>;  // exposition only
 ```
 ### Header `<map>` synopsis <a id="associative.map.syn">[[associative.map.syn]]</a>
 ``` cpp
-#include <initializer_list>
 namespace std {
   // [map], class template map
   template<class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T>>>
     class map;
   template<class Key, class T, class Compare, class Allocator>
     bool operator==(const map<Key, T, Compare, Allocator>& x,
                     const map<Key, T, Compare, Allocator>& y);
   template<class Key, class T, class Compare, class Allocator>
- bool operator< (const map<Key, T, Compare, Allocator>& x,
- const map<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator!=(const map<Key, T, Compare, Allocator>& x,
-                    const map<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator> (const map<Key, T, Compare, Allocator>& x,
-                    const map<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator>=(const map<Key, T, Compare, Allocator>& x,
-                    const map<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator<=(const map<Key, T, Compare, Allocator>& x,
                   const map<Key, T, Compare, Allocator>& y);
   template<class Key, class T, class Compare, class Allocator>
     void swap(map<Key, T, Compare, Allocator>& x,
               map<Key, T, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
   // [multimap], class template multimap
   template<class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T>>>
     class multimap;
   template<class Key, class T, class Compare, class Allocator>
     bool operator==(const multimap<Key, T, Compare, Allocator>& x,
                     const multimap<Key, T, Compare, Allocator>& y);
   template<class Key, class T, class Compare, class Allocator>
- bool operator< (const multimap<Key, T, Compare, Allocator>& x,
- const multimap<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator!=(const multimap<Key, T, Compare, Allocator>& x,
-                    const multimap<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator> (const multimap<Key, T, Compare, Allocator>& x,
-                    const multimap<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator>=(const multimap<Key, T, Compare, Allocator>& x,
-                    const multimap<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator<=(const multimap<Key, T, Compare, Allocator>& x,
                   const multimap<Key, T, Compare, Allocator>& y);
   template<class Key, class T, class Compare, class Allocator>
     void swap(multimap<Key, T, Compare, Allocator>& x,
               multimap<Key, T, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
   namespace pmr {
     template<class Key, class T, class Compare = less<Key>>
       using map = std::map<Key, T, Compare,
                            polymorphic_allocator<pair<const Key, T>>>;
@@ -3312,107 +3409,91 @@ namespace std {
 ```
 ### Header `<set>` synopsis <a id="associative.set.syn">[[associative.set.syn]]</a>
 ``` cpp
-#include <initializer_list>
 namespace std {
   // [set], class template set
-  template <class Key, class Compare = less<Key>,
-            class Allocator = allocator<Key>>
     class set;
   template<class Key, class Compare, class Allocator>
     bool operator==(const set<Key, Compare, Allocator>& x,
                     const set<Key, Compare, Allocator>& y);
   template<class Key, class Compare, class Allocator>
- bool operator< (const set<Key, Compare, Allocator>& x,
- const set<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator!=(const set<Key, Compare, Allocator>& x,
-                    const set<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator> (const set<Key, Compare, Allocator>& x,
-                    const set<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator>=(const set<Key, Compare, Allocator>& x,
-                    const set<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator<=(const set<Key, Compare, Allocator>& x,
-                    const set<Key, Compare, Allocator>& y);
   template<class Key, class Compare, class Allocator>
     void swap(set<Key, Compare, Allocator>& x,
               set<Key, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
   // [multiset], class template multiset
-  template <class Key, class Compare = less<Key>,
-            class Allocator = allocator<Key>>
     class multiset;
   template<class Key, class Compare, class Allocator>
     bool operator==(const multiset<Key, Compare, Allocator>& x,
                     const multiset<Key, Compare, Allocator>& y);
   template<class Key, class Compare, class Allocator>
- bool operator< (const multiset<Key, Compare, Allocator>& x,
- const multiset<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator!=(const multiset<Key, Compare, Allocator>& x,
-                    const multiset<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator> (const multiset<Key, Compare, Allocator>& x,
-                    const multiset<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator>=(const multiset<Key, Compare, Allocator>& x,
-                    const multiset<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator<=(const multiset<Key, Compare, Allocator>& x,
-                    const multiset<Key, Compare, Allocator>& y);
   template<class Key, class Compare, class Allocator>
     void swap(multiset<Key, Compare, Allocator>& x,
               multiset<Key, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
   namespace pmr {
     template<class Key, class Compare = less<Key>>
-      using set = std::set<Key, Compare,
-                           polymorphic_allocator<Key>>;
     template<class Key, class Compare = less<Key>>
-      using multiset = std::multiset<Key, Compare,
-                                     polymorphic_allocator<Key>>;
   }
 }
 ```
 ### Class template `map` <a id="map">[[map]]</a>
-#### Class template `map` overview <a id="map.overview">[[map.overview]]</a>
 A `map` is an associative container that supports unique keys (contains
 at most one of each key value) and provides for fast retrieval of values
 of another type `T` based on the keys. The `map` class supports
 bidirectional iterators.
-A `map` satisfies all of the requirements of a container, of a
-reversible container ([[container.requirements]]), of an associative
-container ([[associative.reqmts]]), and of an allocator-aware container
-(Table  [[tab:containers.allocatoraware]]). A `map` also provides most
-operations described in  [[associative.reqmts]] for unique keys. This
-means that a `map` supports the `a_uniq` operations in
-[[associative.reqmts]] but not the `a_eq` operations. For a `map<Key,T>`
-the `key_type` is `Key` and the `value_type` is `pair<const Key,T>`.
-Descriptions are provided here only for operations on `map` that are not
-described in one of those tables or for operations where there is
-additional semantic information.
 ``` cpp
 namespace std {
   template<class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T>>>
   class map {
   public:
-    // types:
     using key_type               = Key;
     using mapped_type            = T;
     using value_type             = pair<const Key, T>;
     using key_compare            = Compare;
     using allocator_type         = Allocator;
@@ -3425,11 +3506,11 @@ namespace std {
     using iterator               = implementation-defined  // type of map::iterator; // see [container.requirements]
     using const_iterator         = implementation-defined  // type of map::const_iterator; // see [container.requirements]
     using reverse_iterator       = std::reverse_iterator<iterator>;
     using const_reverse_iterator = std::reverse_iterator<const_iterator>;
     using node_type              = unspecified;
-    using insert_return_type     = INSERT_RETURN_TYPE<iterator, node_type>;
     class value_compare {
       friend class map;
     protected:
       Compare comp;
@@ -3465,11 +3546,11 @@ namespace std {
       noexcept(allocator_traits<Allocator>::is_always_equal::value &&
                is_nothrow_move_assignable_v<Compare>);
     map& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
-    // iterators:
     iterator               begin() noexcept;
     const_iterator         begin() const noexcept;
     iterator               end() noexcept;
     const_iterator         end() const noexcept;
@@ -3481,20 +3562,20 @@ namespace std {
     const_iterator         cbegin() const noexcept;
     const_iterator         cend() const noexcept;
     const_reverse_iterator crbegin() const noexcept;
     const_reverse_iterator crend() const noexcept;
-    // capacity:
-    bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
     // [map.access], element access
- T& operator[](const key_type& x);
- T& operator[](key_type&& x);
- T&       at(const key_type& x);
-    const T& at(const key_type& x) const;
     // [map.modifiers], modifiers
     template<class... Args> pair<iterator, bool> emplace(Args&&... args);
     template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
     pair<iterator, bool> insert(const value_type& x);
@@ -3546,23 +3627,26 @@ namespace std {
     template<class C2>
       void merge(multimap<Key, T, C2, Allocator>& source);
     template<class C2>
       void merge(multimap<Key, T, C2, Allocator>&& source);
-    // observers:
     key_compare key_comp() const;
     value_compare value_comp() const;
-    // map operations:
     iterator       find(const key_type& x);
     const_iterator find(const key_type& x) const;
     template<class K> iterator       find(const K& x);
     template<class K> const_iterator find(const K& x) const;
     size_type      count(const key_type& x) const;
     template<class K> size_type count(const K& x) const;
     iterator       lower_bound(const key_type& x);
     const_iterator lower_bound(const key_type& x) const;
     template<class K> iterator       lower_bound(const K& x);
     template<class K> const_iterator lower_bound(const K& x) const;
@@ -3577,56 +3661,37 @@ namespace std {
       pair<iterator, iterator>             equal_range(const K& x);
     template<class K>
       pair<const_iterator, const_iterator> equal_range(const K& x) const;
   };
-  template<class InputIterator, class Compare = less<iter_key_t<InputIterator>>,
-           class Allocator = allocator<iter_to_alloc_t<InputIterator>>>
     map(InputIterator, InputIterator, Compare = Compare(), Allocator = Allocator())
-      -> map<iter_key_t<InputIterator>, iter_val_t<InputIterator>, Compare, Allocator>;
   template<class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T>>>
-    map(initializer_list<pair<const Key, T>>, Compare = Compare(), Allocator = Allocator())
       -> map<Key, T, Compare, Allocator>;
   template<class InputIterator, class Allocator>
     map(InputIterator, InputIterator, Allocator)
-      -> map<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
-             less<iter_key_t<InputIterator>>, Allocator>;
   template<class Key, class T, class Allocator>
-    map(initializer_list<pair<const Key, T>>, Allocator) -> map<Key, T, less<Key>, Allocator>;
- template <class Key, class T, class Compare, class Allocator>
-    bool operator==(const map<Key, T, Compare, Allocator>& x,
-                    const map<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator< (const map<Key, T, Compare, Allocator>& x,
-                    const map<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator!=(const map<Key, T, Compare, Allocator>& x,
-                    const map<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator> (const map<Key, T, Compare, Allocator>& x,
-                    const map<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator>=(const map<Key, T, Compare, Allocator>& x,
-                    const map<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator<=(const map<Key, T, Compare, Allocator>& x,
-                    const map<Key, T, Compare, Allocator>& y);
-  // [map.special], specialized algorithms
   template<class Key, class T, class Compare, class Allocator>
     void swap(map<Key, T, Compare, Allocator>& x,
               map<Key, T, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
-#### `map` constructors, copy, and assignment <a id="map.cons">[[map.cons]]</a>
 ``` cpp
 explicit map(const Compare& comp, const Allocator& = Allocator());
 ```
@@ -3646,62 +3711,61 @@ object and allocator, and inserts elements from the range \[`first`,
 `last`).
 *Complexity:* Linear in N if the range \[`first`, `last`) is already
 sorted using `comp` and otherwise N log N, where N is `last - first`.
-#### `map` element access <a id="map.access">[[map.access]]</a>
 ``` cpp
-T& operator[](const key_type& x);
 ```
 *Effects:* Equivalent to: `return try_emplace(x).first->second;`
 ``` cpp
-T& operator[](key_type&& x);
 ```
 *Effects:* Equivalent to: `return try_emplace(move(x)).first->second;`
 ``` cpp
-T&       at(const key_type& x);
-const T& at(const key_type& x) const;
 ```
 *Returns:* A reference to the `mapped_type` corresponding to `x` in
 `*this`.
 *Throws:* An exception object of type `out_of_range` if no such element
 is present.
 *Complexity:* Logarithmic.
-#### `map` modifiers <a id="map.modifiers">[[map.modifiers]]</a>
 ``` cpp
 template<class P>
   pair<iterator, bool> insert(P&& x);
 template<class P>
   iterator insert(const_iterator position, P&& x);
 ```
 *Effects:* The first form is equivalent to
 `return emplace(std::forward<P>(x))`. The second form is equivalent to
 `return emplace_hint(position, std::forward<P>(x))`.
-*Remarks:* These signatures shall not participate in overload resolution
-unless `is_constructible_v<value_type, P&&>` is `true`.
 ``` cpp
 template<class... Args>
   pair<iterator, bool> try_emplace(const key_type& k, Args&&... args);
 template<class... Args>
   iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args);
 ```
-*Requires:* `value_type` shall be `EmplaceConstructible` into `map` from
-`piecewise_construct`, `forward_as_tuple(k)`,
 `forward_as_tuple(std::forward<Args>(args)...)`.
 *Effects:* If the map already contains an element whose key is
 equivalent to `k`, there is no effect. Otherwise inserts an object of
 type `value_type` constructed with `piecewise_construct`,
@@ -3718,12 +3782,12 @@ template <class... Args>
   pair<iterator, bool> try_emplace(key_type&& k, Args&&... args);
 template<class... Args>
   iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args);
 ```
-*Requires:* `value_type` shall be `EmplaceConstructible` into `map` from
-`piecewise_construct`, `forward_as_tuple(std::move(k))`,
 `forward_as_tuple(std::forward<Args>(args)...)`.
 *Effects:* If the map already contains an element whose key is
 equivalent to `k`, there is no effect. Otherwise inserts an object of
 type `value_type` constructed with `piecewise_construct`,
@@ -3741,13 +3805,14 @@ template <class M>
   pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj);
 template<class M>
   iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj);
 ```
-*Requires:* `is_assignable_v<mapped_type&, M&&>` shall be `true`.
-`value_type` shall be `EmplaceConstructible` into `map` from `k`,
-`forward<M>(obj)`.
 *Effects:* If the map already contains an element `e` whose key is
 equivalent to `k`, assigns `std::forward<M>(obj)` to `e.second`.
 Otherwise inserts an object of type `value_type` constructed with `k`,
 `std::forward<M>(obj)`.
@@ -3763,13 +3828,14 @@ template <class M>
   pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj);
 template<class M>
   iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj);
 ```
-*Requires:* `is_assignable_v<mapped_type&, M&&>` shall be `true`.
-`value_type` shall be `EmplaceConstructible` into `map` from `move(k)`,
-`forward<M>(obj)`.
 *Effects:* If the map already contains an element `e` whose key is
 equivalent to `k`, assigns `std::forward<M>(obj)` to `e.second`.
 Otherwise inserts an object of type `value_type` constructed with
 `std::move(k)`, `std::forward<M>(obj)`.
@@ -3778,49 +3844,60 @@ Otherwise inserts an object of type `value_type` constructed with
 pair is `true` if and only if the insertion took place. The returned
 iterator points to the map element whose key is equivalent to `k`.
 *Complexity:* The same as `emplace` and `emplace_hint`, respectively.
-#### `map` specialized algorithms <a id="map.special">[[map.special]]</a>
 ``` cpp
-template <class Key, class T, class Compare, class Allocator>
- void swap(map<Key, T, Compare, Allocator>& x,
- map<Key, T, Compare, Allocator>& y)
-    noexcept(noexcept(x.swap(y)));
 ```
-*Effects:* As if by `x.swap(y)`.
 ### Class template `multimap` <a id="multimap">[[multimap]]</a>
-#### Class template `multimap` overview <a id="multimap.overview">[[multimap.overview]]</a>
 A `multimap` is an associative container that supports equivalent keys
 (possibly containing multiple copies of the same key value) and provides
 for fast retrieval of values of another type `T` based on the keys. The
 `multimap` class supports bidirectional iterators.
-A `multimap` satisfies all of the requirements of a container and of a
-reversible container ([[container.requirements]]), of an associative
-container ([[associative.reqmts]]), and of an allocator-aware container
-(Table  [[tab:containers.allocatoraware]]). A `multimap` also provides
-most operations described in  [[associative.reqmts]] for equal keys.
-This means that a `multimap` supports the `a_eq` operations in
-[[associative.reqmts]] but not the `a_uniq` operations. For a
-`multimap<Key,T>` the `key_type` is `Key` and the `value_type` is
-`pair<const Key,T>`. Descriptions are provided here only for operations
-on `multimap` that are not described in one of those tables or for
-operations where there is additional semantic information.
 ``` cpp
 namespace std {
   template<class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T>>>
   class multimap {
   public:
-    // types:
     using key_type               = Key;
     using mapped_type            = T;
     using value_type             = pair<const Key, T>;
     using key_compare            = Compare;
     using allocator_type         = Allocator;
@@ -3873,11 +3950,11 @@ namespace std {
       noexcept(allocator_traits<Allocator>::is_always_equal::value &&
                is_nothrow_move_assignable_v<Compare>);
     multimap& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
-    // iterators:
     iterator               begin() noexcept;
     const_iterator         begin() const noexcept;
     iterator               end() noexcept;
     const_iterator         end() const noexcept;
@@ -3889,12 +3966,12 @@ namespace std {
     const_iterator         cbegin() const noexcept;
     const_iterator         cend() const noexcept;
     const_reverse_iterator crbegin() const noexcept;
     const_reverse_iterator crend() const noexcept;
-    // capacity:
-    bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
     // [multimap.modifiers], modifiers
     template<class... Args> iterator emplace(Args&&... args);
@@ -3930,23 +4007,26 @@ namespace std {
     template<class C2>
       void merge(map<Key, T, C2, Allocator>& source);
     template<class C2>
       void merge(map<Key, T, C2, Allocator>&& source);
-    // observers:
     key_compare key_comp() const;
     value_compare value_comp() const;
-    // map operations:
     iterator       find(const key_type& x);
     const_iterator find(const key_type& x) const;
     template<class K> iterator       find(const K& x);
     template<class K> const_iterator find(const K& x) const;
     size_type      count(const key_type& x) const;
     template<class K> size_type count(const K& x) const;
     iterator       lower_bound(const key_type& x);
     const_iterator lower_bound(const key_type& x) const;
     template<class K> iterator       lower_bound(const K& x);
     template<class K> const_iterator lower_bound(const K& x) const;
@@ -3961,57 +4041,39 @@ namespace std {
       pair<iterator, iterator>             equal_range(const K& x);
     template<class K>
       pair<const_iterator, const_iterator> equal_range(const K& x) const;
   };
-  template<class InputIterator, class Compare = less<iter_key_t<InputIterator>>,
-           class Allocator = allocator<iter_to_alloc_t<InputIterator>>>
     multimap(InputIterator, InputIterator, Compare = Compare(), Allocator = Allocator())
-      -> multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>, Compare, Allocator>;
   template<class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T>>>
-    multimap(initializer_list<pair<const Key, T>>, Compare = Compare(), Allocator = Allocator())
       -> multimap<Key, T, Compare, Allocator>;
   template<class InputIterator, class Allocator>
     multimap(InputIterator, InputIterator, Allocator)
-      -> multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
-                  less<iter_key_t<InputIterator>>, Allocator>;
   template<class Key, class T, class Allocator>
-    multimap(initializer_list<pair<const Key, T>>, Allocator)
       -> multimap<Key, T, less<Key>, Allocator>;
- template <class Key, class T, class Compare, class Allocator>
-    bool operator==(const multimap<Key, T, Compare, Allocator>& x,
-                    const multimap<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator< (const multimap<Key, T, Compare, Allocator>& x,
-                    const multimap<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator!=(const multimap<Key, T, Compare, Allocator>& x,
-                    const multimap<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator> (const multimap<Key, T, Compare, Allocator>& x,
-                    const multimap<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator>=(const multimap<Key, T, Compare, Allocator>& x,
-                    const multimap<Key, T, Compare, Allocator>& y);
-  template <class Key, class T, class Compare, class Allocator>
-    bool operator<=(const multimap<Key, T, Compare, Allocator>& x,
-                    const multimap<Key, T, Compare, Allocator>& y);
-  // [multimap.special], specialized algorithms
   template<class Key, class T, class Compare, class Allocator>
     void swap(multimap<Key, T, Compare, Allocator>& x,
               multimap<Key, T, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
-#### `multimap` constructors <a id="multimap.cons">[[multimap.cons]]</a>
 ``` cpp
 explicit multimap(const Compare& comp, const Allocator& = Allocator());
 ```
@@ -4032,62 +4094,71 @@ object and allocator, and inserts elements from the range \[`first`,
 `last`).
 *Complexity:* Linear in N if the range \[`first`, `last`) is already
 sorted using `comp` and otherwise N log N, where N is `last - first`.
-#### `multimap` modifiers <a id="multimap.modifiers">[[multimap.modifiers]]</a>
 ``` cpp
 template<class P> iterator insert(P&& x);
 template<class P> iterator insert(const_iterator position, P&& x);
 ```
 *Effects:* The first form is equivalent to
 `return emplace(std::forward<P>(x))`. The second form is equivalent to
 `return emplace_hint(position, std::forward<P>(x))`.
-*Remarks:* These signatures shall not participate in overload resolution
-unless `is_constructible_v<value_type, P&&>` is `true`.
-#### `multimap` specialized algorithms <a id="multimap.special">[[multimap.special]]</a>
 ``` cpp
-template <class Key, class T, class Compare, class Allocator>
- void swap(multimap<Key, T, Compare, Allocator>& x,
- multimap<Key, T, Compare, Allocator>& y)
-    noexcept(noexcept(x.swap(y)));
 ```
-*Effects:* As if by `x.swap(y)`.
 ### Class template `set` <a id="set">[[set]]</a>
-#### Class template `set` overview <a id="set.overview">[[set.overview]]</a>
 A `set` is an associative container that supports unique keys (contains
 at most one of each key value) and provides for fast retrieval of the
 keys themselves. The `set` class supports bidirectional iterators.
-A `set` satisfies all of the requirements of a container, of a
-reversible container ([[container.requirements]]), of an associative
-container ([[associative.reqmts]]), and of an allocator-aware container
-(Table  [[tab:containers.allocatoraware]]). A `set` also provides most
-operations described in  [[associative.reqmts]] for unique keys. This
-means that a `set` supports the `a_uniq` operations in
-[[associative.reqmts]] but not the `a_eq` operations. For a `set<Key>`
-both the `key_type` and `value_type` are `Key`. Descriptions are
-provided here only for operations on `set` that are not described in one
-of these tables and for operations where there is additional semantic
-information.
 ``` cpp
 namespace std {
   template<class Key, class Compare = less<Key>,
            class Allocator = allocator<Key>>
   class set {
   public:
-    // types:
     using key_type               = Key;
     using key_compare            = Compare;
     using value_type             = Key;
     using value_compare          = Compare;
     using allocator_type         = Allocator;
@@ -4100,11 +4171,11 @@ namespace std {
     using iterator               = implementation-defined  // type of set::iterator; // see [container.requirements]
     using const_iterator         = implementation-defined  // type of set::const_iterator; // see [container.requirements]
     using reverse_iterator       = std::reverse_iterator<iterator>;
     using const_reverse_iterator = std::reverse_iterator<const_iterator>;
     using node_type              = unspecified;
-    using insert_return_type     = INSERT_RETURN_TYPE<iterator, node_type>;
     // [set.cons], construct/copy/destroy
     set() : set(Compare()) { }
     explicit set(const Compare& comp, const Allocator& = Allocator());
     template<class InputIterator>
@@ -4128,11 +4199,11 @@ namespace std {
       noexcept(allocator_traits<Allocator>::is_always_equal::value &&
                is_nothrow_move_assignable_v<Compare>);
     set& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
-    // iterators:
     iterator               begin() noexcept;
     const_iterator         begin() const noexcept;
     iterator               end() noexcept;
     const_iterator         end() const noexcept;
@@ -4144,16 +4215,16 @@ namespace std {
     const_iterator         cbegin() const noexcept;
     const_iterator         cend() const noexcept;
     const_reverse_iterator crbegin() const noexcept;
     const_reverse_iterator crend() const noexcept;
-    // capacity:
-    bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
-    // modifiers:
     template<class... Args> pair<iterator, bool> emplace(Args&&... args);
     template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
     pair<iterator,bool> insert(const value_type& x);
     pair<iterator,bool> insert(value_type&& x);
     iterator insert(const_iterator position, const value_type& x);
@@ -4183,23 +4254,26 @@ namespace std {
     template<class C2>
       void merge(multiset<Key, C2, Allocator>& source);
     template<class C2>
       void merge(multiset<Key, C2, Allocator>&& source);
-    // observers:
     key_compare key_comp() const;
     value_compare value_comp() const;
-    // set operations:
     iterator       find(const key_type& x);
     const_iterator find(const key_type& x) const;
     template<class K> iterator       find(const K& x);
     template<class K> const_iterator find(const K& x) const;
     size_type      count(const key_type& x) const;
     template<class K> size_type count(const K& x) const;
     iterator       lower_bound(const key_type& x);
     const_iterator lower_bound(const key_type& x) const;
     template<class K> iterator       lower_bound(const K& x);
     template<class K> const_iterator lower_bound(const K& x) const;
@@ -4215,56 +4289,37 @@ namespace std {
     template<class K>
       pair<const_iterator, const_iterator> equal_range(const K& x) const;
   };
   template<class InputIterator,
-           class Compare = less<typename iterator_traits<InputIterator>::value_type>,
-           class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
     set(InputIterator, InputIterator,
         Compare = Compare(), Allocator = Allocator())
-      -> set<typename iterator_traits<InputIterator>::value_type, Compare, Allocator>;
   template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
     set(initializer_list<Key>, Compare = Compare(), Allocator = Allocator())
       -> set<Key, Compare, Allocator>;
   template<class InputIterator, class Allocator>
     set(InputIterator, InputIterator, Allocator)
-      -> set<typename iterator_traits<InputIterator>::value_type,
-             less<typename iterator_traits<InputIterator>::value_type>, Allocator>;
   template<class Key, class Allocator>
     set(initializer_list<Key>, Allocator) -> set<Key, less<Key>, Allocator>;
- template <class Key, class Compare, class Allocator>
-    bool operator==(const set<Key, Compare, Allocator>& x,
-                    const set<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator< (const set<Key, Compare, Allocator>& x,
-                    const set<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator!=(const set<Key, Compare, Allocator>& x,
-                    const set<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator> (const set<Key, Compare, Allocator>& x,
-                    const set<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator>=(const set<Key, Compare, Allocator>& x,
-                    const set<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator<=(const set<Key, Compare, Allocator>& x,
-                    const set<Key, Compare, Allocator>& y);
-  // [set.special], specialized algorithms
   template<class Key, class Compare, class Allocator>
     void swap(set<Key, Compare, Allocator>& x,
               set<Key, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
-#### `set` constructors, copy, and assignment <a id="set.cons">[[set.cons]]</a>
 ``` cpp
 explicit set(const Compare& comp, const Allocator& = Allocator());
 ```
@@ -4284,49 +4339,60 @@ object and allocator, and inserts elements from the range \[`first`,
 `last`).
 *Complexity:* Linear in N if the range \[`first`, `last`) is already
 sorted using `comp` and otherwise N log N, where N is `last - first`.
-#### `set` specialized algorithms <a id="set.special">[[set.special]]</a>
 ``` cpp
-template <class Key, class Compare, class Allocator>
- void swap(set<Key, Compare, Allocator>& x,
- set<Key, Compare, Allocator>& y)
-    noexcept(noexcept(x.swap(y)));
 ```
-*Effects:* As if by `x.swap(y)`.
 ### Class template `multiset` <a id="multiset">[[multiset]]</a>
-#### Class template `multiset` overview <a id="multiset.overview">[[multiset.overview]]</a>
 A `multiset` is an associative container that supports equivalent keys
 (possibly contains multiple copies of the same key value) and provides
 for fast retrieval of the keys themselves. The `multiset` class supports
 bidirectional iterators.
-A `multiset` satisfies all of the requirements of a container, of a
-reversible container ([[container.requirements]]), of an associative
-container ([[associative.reqmts]]), and of an allocator-aware container
-(Table  [[tab:containers.allocatoraware]]). `multiset` also provides
-most operations described in  [[associative.reqmts]] for duplicate keys.
-This means that a `multiset` supports the `a_eq` operations in
-[[associative.reqmts]] but not the `a_uniq` operations. For a
-`multiset<Key>` both the `key_type` and `value_type` are `Key`.
-Descriptions are provided here only for operations on `multiset` that
-are not described in one of these tables and for operations where there
-is additional semantic information.
 ``` cpp
 namespace std {
   template<class Key, class Compare = less<Key>,
            class Allocator = allocator<Key>>
   class multiset {
   public:
-    // types:
     using key_type               = Key;
     using key_compare            = Compare;
     using value_type             = Key;
     using value_compare          = Compare;
     using allocator_type         = Allocator;
@@ -4366,11 +4432,11 @@ namespace std {
       noexcept(allocator_traits<Allocator>::is_always_equal::value &&
                is_nothrow_move_assignable_v<Compare>);
     multiset& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
-    // iterators:
     iterator               begin() noexcept;
     const_iterator         begin() const noexcept;
     iterator               end() noexcept;
     const_iterator         end() const noexcept;
@@ -4382,16 +4448,16 @@ namespace std {
     const_iterator         cbegin() const noexcept;
     const_iterator         cend() const noexcept;
     const_reverse_iterator crbegin() const noexcept;
     const_reverse_iterator crend() const noexcept;
-    // capacity:
-    bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
-    // modifiers:
     template<class... Args> iterator emplace(Args&&... args);
     template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
     iterator insert(const value_type& x);
     iterator insert(value_type&& x);
     iterator insert(const_iterator position, const value_type& x);
@@ -4421,23 +4487,26 @@ namespace std {
     template<class C2>
       void merge(set<Key, C2, Allocator>& source);
     template<class C2>
       void merge(set<Key, C2, Allocator>&& source);
-    // observers:
     key_compare key_comp() const;
     value_compare value_comp() const;
-    // set operations:
     iterator       find(const key_type& x);
     const_iterator find(const key_type& x) const;
     template<class K> iterator       find(const K& x);
     template<class K> const_iterator find(const K& x) const;
     size_type      count(const key_type& x) const;
     template<class K> size_type count(const K& x) const;
     iterator       lower_bound(const key_type& x);
     const_iterator lower_bound(const key_type& x) const;
     template<class K> iterator       lower_bound(const K& x);
     template<class K> const_iterator lower_bound(const K& x) const;
@@ -4453,56 +4522,37 @@ namespace std {
     template<class K>
       pair<const_iterator, const_iterator> equal_range(const K& x) const;
   };
   template<class InputIterator,
-           class Compare = less<typename iterator_traits<InputIterator>::value_type>,
-           class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
     multiset(InputIterator, InputIterator,
              Compare = Compare(), Allocator = Allocator())
-      -> multiset<typename iterator_traits<InputIterator>::value_type, Compare, Allocator>;
   template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
     multiset(initializer_list<Key>, Compare = Compare(), Allocator = Allocator())
       -> multiset<Key, Compare, Allocator>;
   template<class InputIterator, class Allocator>
     multiset(InputIterator, InputIterator, Allocator)
-      -> multiset<typename iterator_traits<InputIterator>::value_type,
-                  less<typename iterator_traits<InputIterator>::value_type>, Allocator>;
   template<class Key, class Allocator>
     multiset(initializer_list<Key>, Allocator) -> multiset<Key, less<Key>, Allocator>;
- template <class Key, class Compare, class Allocator>
-    bool operator==(const multiset<Key, Compare, Allocator>& x,
-                    const multiset<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator< (const multiset<Key, Compare, Allocator>& x,
-                    const multiset<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator!=(const multiset<Key, Compare, Allocator>& x,
-                    const multiset<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator> (const multiset<Key, Compare, Allocator>& x,
-                    const multiset<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator>=(const multiset<Key, Compare, Allocator>& x,
-                    const multiset<Key, Compare, Allocator>& y);
-  template <class Key, class Compare, class Allocator>
-    bool operator<=(const multiset<Key, Compare, Allocator>& x,
-                    const multiset<Key, Compare, Allocator>& y);
-  // [multiset.special], specialized algorithms
   template<class Key, class Compare, class Allocator>
     void swap(multiset<Key, Compare, Allocator>& x,
               multiset<Key, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
-#### `multiset` constructors <a id="multiset.cons">[[multiset.cons]]</a>
 ``` cpp
 explicit multiset(const Compare& comp, const Allocator& = Allocator());
 ```
@@ -4522,37 +4572,50 @@ object and allocator, and inserts elements from the range \[`first`,
 `last`).
 *Complexity:* Linear in N if the range \[`first`, `last`) is already
 sorted using `comp` and otherwise N log N, where N is `last - first`.
-#### `multiset` specialized algorithms <a id="multiset.special">[[multiset.special]]</a>
 ``` cpp
-template <class Key, class Compare, class Allocator>
- void swap(multiset<Key, Compare, Allocator>& x,
- multiset<Key, Compare, Allocator>& y)
-    noexcept(noexcept(x.swap(y)));
 ```
-*Effects:* As if by `x.swap(y)`.
 ## Unordered associative containers <a id="unord">[[unord]]</a>
 ### In general <a id="unord.general">[[unord.general]]</a>
 The header `<unordered_map>` defines the class templates `unordered_map`
 and `unordered_multimap`; the header `<unordered_set>` defines the class
 templates `unordered_set` and `unordered_multiset`.
-The exposition-only alias templates `iter_key_t`, `iter_val_t`, and
-`iter_to_alloc_t` defined in [[associative.general]] may appear in
-deduction guides for unordered containers.
 ### Header `<unordered_map>` synopsis <a id="unord.map.syn">[[unord.map.syn]]</a>
 ``` cpp
-#include <initializer_list>
 namespace std {
   // [unord.map], class template unordered_map
   template<class Key,
            class T,
@@ -4567,32 +4630,35 @@ namespace std {
            class Hash = hash<Key>,
            class Pred = equal_to<Key>,
            class Alloc = allocator<pair<const Key, T>>>
     class unordered_multimap;
   template<class Key, class T, class Hash, class Pred, class Alloc>
     void swap(unordered_map<Key, T, Hash, Pred, Alloc>& x,
               unordered_map<Key, T, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
   template<class Key, class T, class Hash, class Pred, class Alloc>
     void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x,
               unordered_multimap<Key, T, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
-  template <class Key, class T, class Hash, class Pred, class Alloc>
- bool operator==(const unordered_map<Key, T, Hash, Pred, Alloc>& a,
-                    const unordered_map<Key, T, Hash, Pred, Alloc>& b);
-  template <class Key, class T, class Hash, class Pred, class Alloc>
-    bool operator!=(const unordered_map<Key, T, Hash, Pred, Alloc>& a,
-                    const unordered_map<Key, T, Hash, Pred, Alloc>& b);
-  template <class Key, class T, class Hash, class Pred, class Alloc>
-    bool operator==(const unordered_multimap<Key, T, Hash, Pred, Alloc>& a,
-                    const unordered_multimap<Key, T, Hash, Pred, Alloc>& b);
-  template <class Key, class T, class Hash, class Pred, class Alloc>
-    bool operator!=(const unordered_multimap<Key, T, Hash, Pred, Alloc>& a,
-                    const unordered_multimap<Key, T, Hash, Pred, Alloc>& b);
   namespace pmr {
     template<class Key,
              class T,
              class Hash = hash<Key>,
@@ -4613,11 +4679,12 @@ namespace std {
 ```
 ### Header `<unordered_set>` synopsis <a id="unord.set.syn">[[unord.set.syn]]</a>
 ``` cpp
-#include <initializer_list>
 namespace std {
   // [unord.set], class template unordered_set
   template<class Key,
            class Hash = hash<Key>,
@@ -4630,32 +4697,35 @@ namespace std {
            class Hash = hash<Key>,
            class Pred = equal_to<Key>,
            class Alloc = allocator<Key>>
     class unordered_multiset;
   template<class Key, class Hash, class Pred, class Alloc>
     void swap(unordered_set<Key, Hash, Pred, Alloc>& x,
               unordered_set<Key, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
   template<class Key, class Hash, class Pred, class Alloc>
     void swap(unordered_multiset<Key, Hash, Pred, Alloc>& x,
               unordered_multiset<Key, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
-  template <class Key, class Hash, class Pred, class Alloc>
- bool operator==(const unordered_set<Key, Hash, Pred, Alloc>& a,
-                    const unordered_set<Key, Hash, Pred, Alloc>& b);
-  template <class Key, class Hash, class Pred, class Alloc>
-    bool operator!=(const unordered_set<Key, Hash, Pred, Alloc>& a,
-                    const unordered_set<Key, Hash, Pred, Alloc>& b);
-  template <class Key, class Hash, class Pred, class Alloc>
-    bool operator==(const unordered_multiset<Key, Hash, Pred, Alloc>& a,
-                    const unordered_multiset<Key, Hash, Pred, Alloc>& b);
-  template <class Key, class Hash, class Pred, class Alloc>
-    bool operator!=(const unordered_multiset<Key, Hash, Pred, Alloc>& a,
-                    const unordered_multiset<Key, Hash, Pred, Alloc>& b);
   namespace pmr {
     template<class Key,
              class Hash = hash<Key>,
              class Pred = equal_to<Key>>
@@ -4671,40 +4741,40 @@ namespace std {
 }
 ```
 ### Class template `unordered_map` <a id="unord.map">[[unord.map]]</a>
-#### Class template `unordered_map` overview <a id="unord.map.overview">[[unord.map.overview]]</a>
 An `unordered_map` is an unordered associative container that supports
 unique keys (an `unordered_map` contains at most one of each key value)
 and that associates values of another type `mapped_type` with the keys.
 The `unordered_map` class supports forward iterators.
-An `unordered_map` satisfies all of the requirements of a container, of
-an unordered associative container, and of an allocator-aware container
-(Table  [[tab:containers.allocatoraware]]). It provides the operations
-described in the preceding requirements table for unique keys; that is,
-an `unordered_map` supports the `a_uniq` operations in that table, not
-the `a_eq` operations. For an `unordered_map<Key, T>` the `key type` is
 `Key`, the mapped type is `T`, and the value type is
 `pair<const Key, T>`.
-This section only describes operations on `unordered_map` that are not
-described in one of the requirement tables, or for which there is
-additional semantic information.
 ``` cpp
 namespace std {
   template<class Key,
            class T,
            class Hash = hash<Key>,
            class Pred = equal_to<Key>,
            class Allocator = allocator<pair<const Key, T>>>
   class unordered_map {
   public:
-    // types:
     using key_type             = Key;
     using mapped_type          = T;
     using value_type           = pair<const Key, T>;
     using hasher               = Hash;
     using key_equal            = Pred;
@@ -4719,11 +4789,11 @@ namespace std {
     using iterator             = implementation-defined  // type of unordered_map::iterator; // see [container.requirements]
     using const_iterator       = implementation-defined  // type of unordered_map::const_iterator; // see [container.requirements]
     using local_iterator       = implementation-defined  // type of unordered_map::local_iterator; // see [container.requirements]
     using const_local_iterator = implementation-defined  // type of unordered_map::const_local_iterator; // see [container.requirements]
     using node_type            = unspecified;
-    using insert_return_type   = INSERT_RETURN_TYPE<iterator, node_type>;
     // [unord.map.cnstr], construct/copy/destroy
     unordered_map();
     explicit unordered_map(size_type n,
                            const hasher& hf = hasher(),
@@ -4768,20 +4838,20 @@ namespace std {
                is_nothrow_move_assignable_v<Hash> &&
                is_nothrow_move_assignable_v<Pred>);
     unordered_map& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
-    // iterators:
     iterator       begin() noexcept;
     const_iterator begin() const noexcept;
     iterator       end() noexcept;
     const_iterator end() const noexcept;
     const_iterator cbegin() const noexcept;
     const_iterator cend() const noexcept;
-    // capacity:
-    bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
     // [unord.map.modifiers], modifiers
     template<class... Args> pair<iterator, bool> emplace(Args&&... args);
@@ -4834,28 +4904,42 @@ namespace std {
     template<class H2, class P2>
       void merge(unordered_multimap<Key, T, H2, P2, Allocator>& source);
     template<class H2, class P2>
       void merge(unordered_multimap<Key, T, H2, P2, Allocator>&& source);
-    // observers:
     hasher hash_function() const;
     key_equal key_eq() const;
-    // map operations:
     iterator         find(const key_type& k);
     const_iterator   find(const key_type& k) const;
     size_type        count(const key_type& k) const;
     pair<iterator, iterator>               equal_range(const key_type& k);
     pair<const_iterator, const_iterator>   equal_range(const key_type& k) const;
     // [unord.map.elem], element access
     mapped_type& operator[](const key_type& k);
     mapped_type& operator[](key_type&& k);
     mapped_type& at(const key_type& k);
     const mapped_type& at(const key_type& k) const;
-    // bucket interface:
     size_type bucket_count() const noexcept;
     size_type max_bucket_count() const noexcept;
     size_type bucket_size(size_type n) const;
     size_type bucket(const key_type& k) const;
     local_iterator begin(size_type n);
@@ -4863,73 +4947,66 @@ namespace std {
     local_iterator end(size_type n);
     const_local_iterator end(size_type n) const;
     const_local_iterator cbegin(size_type n) const;
     const_local_iterator cend(size_type n) const;
-    // hash policy:
     float load_factor() const noexcept;
     float max_load_factor() const noexcept;
     void max_load_factor(float z);
     void rehash(size_type n);
     void reserve(size_type n);
   };
   template<class InputIterator,
-           class Hash = hash<iter_key_t<InputIterator>>,
-           class Pred = equal_to<iter_key_t<InputIterator>>,
-           class Allocator = allocator<iter_to_alloc_t<InputIterator>>>
     unordered_map(InputIterator, InputIterator, typename see below::size_type = see below,
                   Hash = Hash(), Pred = Pred(), Allocator = Allocator())
-      -> unordered_map<iter_key_t<InputIterator>, iter_value_t<InputIterator>, Hash, Pred,
                        Allocator>;
   template<class Key, class T, class Hash = hash<Key>,
            class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>>
-    unordered_map(initializer_list<pair<const Key, T>>,
                   typename see below::size_type = see below, Hash = Hash(),
                   Pred = Pred(), Allocator = Allocator())
       -> unordered_map<Key, T, Hash, Pred, Allocator>;
   template<class InputIterator, class Allocator>
     unordered_map(InputIterator, InputIterator, typename see below::size_type, Allocator)
-      -> unordered_map<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
-                       hash<iter_key_t<InputIterator>>, equal_to<iter_key_t<InputIterator>>,
-                       Allocator>;
   template<class InputIterator, class Allocator>
     unordered_map(InputIterator, InputIterator, Allocator)
-      -> unordered_map<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
-                       hash<iter_key_t<InputIterator>>, equal_to<iter_key_t<InputIterator>>,
-                       Allocator>;
   template<class InputIterator, class Hash, class Allocator>
     unordered_map(InputIterator, InputIterator, typename see below::size_type, Hash, Allocator)
-      -> unordered_map<iter_key_t<InputIterator>, iter_val_t<InputIterator>, Hash,
-                       equal_to<iter_key_t<InputIterator>>, Allocator>;
-  template<class Key, class T, typename Allocator>
-    unordered_map(initializer_list<pair<const Key, T>>, typename see below::size_type,
                   Allocator)
       -> unordered_map<Key, T, hash<Key>, equal_to<Key>, Allocator>;
-  template<class Key, class T, typename Allocator>
-    unordered_map(initializer_list<pair<const Key, T>>, Allocator)
       -> unordered_map<Key, T, hash<Key>, equal_to<Key>, Allocator>;
   template<class Key, class T, class Hash, class Allocator>
-    unordered_map(initializer_list<pair<const Key, T>>, typename see below::size_type, Hash,
                   Allocator)
       -> unordered_map<Key, T, Hash, equal_to<Key>, Allocator>;
- template <class Key, class T, class Hash, class Pred, class Alloc>
-    bool operator==(const unordered_map<Key, T, Hash, Pred, Alloc>& a,
-                    const unordered_map<Key, T, Hash, Pred, Alloc>& b);
-  template <class Key, class T, class Hash, class Pred, class Alloc>
-    bool operator!=(const unordered_map<Key, T, Hash, Pred, Alloc>& a,
-                    const unordered_map<Key, T, Hash, Pred, Alloc>& b);
-  // [unord.map.swap], swap
   template<class Key, class T, class Hash, class Pred, class Alloc>
     void swap(unordered_map<Key, T, Hash, Pred, Alloc>& x,
               unordered_map<Key, T, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
 }
@@ -4937,11 +5014,11 @@ namespace std {
 A `size_type` parameter type in an `unordered_map` deduction guide
 refers to the `size_type` member type of the type deduced by the
 deduction guide.
-#### `unordered_map` constructors <a id="unord.map.cnstr">[[unord.map.cnstr]]</a>
 ``` cpp
 unordered_map() : unordered_map(size_type(see below)) { }
 explicit unordered_map(size_type n,
                        const hasher& hf = hasher(),
@@ -4977,11 +5054,11 @@ buckets. If `n` is not provided, the number of buckets is
 `l`) for the first form, or from the range \[`il.begin()`, `il.end()`)
 for the second form. `max_load_factor()` returns `1.0`.
 *Complexity:* Average case linear, worst case quadratic.
-#### `unordered_map` element access <a id="unord.map.elem">[[unord.map.elem]]</a>
 ``` cpp
 mapped_type& operator[](const key_type& k);
 ```
@@ -5002,41 +5079,39 @@ const mapped_type& at(const key_type& k) const;
 whose key is equivalent to `k`.
 *Throws:* An exception object of type `out_of_range` if no such element
 is present.
-#### `unordered_map` modifiers <a id="unord.map.modifiers">[[unord.map.modifiers]]</a>
 ``` cpp
 template<class P>
   pair<iterator, bool> insert(P&& obj);
 ```
 *Effects:* Equivalent to: `return emplace(std::forward<P>(obj));`
-*Remarks:* This signature shall not participate in overload resolution
-unless `is_constructible_v<value_type, P&&>` is `true`.
 ``` cpp
 template<class P>
   iterator insert(const_iterator hint, P&& obj);
 ```
 *Effects:* Equivalent to:
 `return emplace_hint(hint, std::forward<P>(obj));`
-*Remarks:* This signature shall not participate in overload resolution
-unless `is_constructible_v<value_type, P&&>` is `true`.
 ``` cpp
 template<class... Args>
   pair<iterator, bool> try_emplace(const key_type& k, Args&&... args);
 template<class... Args>
   iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args);
 ```
-*Requires:* `value_type` shall be `EmplaceConstructible` into
 `unordered_map` from `piecewise_construct`, `forward_as_tuple(k)`,
 `forward_as_tuple(std::forward<Args>(args)...)`.
 *Effects:* If the map already contains an element whose key is
 equivalent to `k`, there is no effect. Otherwise inserts an object of
@@ -5054,11 +5129,11 @@ template <class... Args>
   pair<iterator, bool> try_emplace(key_type&& k, Args&&... args);
 template<class... Args>
   iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args);
 ```
-*Requires:* `value_type` shall be `EmplaceConstructible` into
 `unordered_map` from `piecewise_construct`,
 `forward_as_tuple(std::move(k))`,
 `forward_as_tuple(std::forward<Args>(args)...)`.
 *Effects:* If the map already contains an element whose key is
@@ -5078,13 +5153,14 @@ template <class M>
   pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj);
 template<class M>
   iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj);
 ```
-*Requires:* `is_assignable_v<mapped_type&, M&&>` shall be `true`.
-`value_type` shall be `EmplaceConstructible` into `unordered_map` from
-`k`, `std::forward<M>(obj)`.
 *Effects:* If the map already contains an element `e` whose key is
 equivalent to `k`, assigns `std::forward<M>(obj)` to `e.second`.
 Otherwise inserts an object of type `value_type` constructed with `k`,
 `std::forward<M>(obj)`.
@@ -5100,13 +5176,14 @@ template <class M>
   pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj);
 template<class M>
   iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj);
 ```
-*Requires:* `is_assignable_v<mapped_type&, M&&>` shall be `true`.
-`value_type` shall be `EmplaceConstructible` into `unordered_map` from
-`std::move(k)`, `std::forward<M>(obj)`.
 *Effects:* If the map already contains an element `e` whose key is
 equivalent to `k`, assigns `std::forward<M>(obj)` to `e.second`.
 Otherwise inserts an object of type `value_type` constructed with
 `std::move(k)`, `std::forward<M>(obj)`.
@@ -5115,54 +5192,65 @@ Otherwise inserts an object of type `value_type` constructed with
 pair is `true` if and only if the insertion took place. The returned
 iterator points to the map element whose key is equivalent to `k`.
 *Complexity:* The same as `emplace` and `emplace_hint`, respectively.
-#### `unordered_map` swap <a id="unord.map.swap">[[unord.map.swap]]</a>
 ``` cpp
-template <class Key, class T, class Hash, class Pred, class Alloc>
- void swap(unordered_map<Key, T, Hash, Pred, Alloc>& x,
- unordered_map<Key, T, Hash, Pred, Alloc>& y)
-    noexcept(noexcept(x.swap(y)));
 ```
-*Effects:* As if by `x.swap(y)`.
 ### Class template `unordered_multimap` <a id="unord.multimap">[[unord.multimap]]</a>
-#### Class template `unordered_multimap` overview <a id="unord.multimap.overview">[[unord.multimap.overview]]</a>
 An `unordered_multimap` is an unordered associative container that
 supports equivalent keys (an instance of `unordered_multimap` may
 contain multiple copies of each key value) and that associates values of
 another type `mapped_type` with the keys. The `unordered_multimap` class
 supports forward iterators.
-An `unordered_multimap` satisfies all of the requirements of a
-container, of an unordered associative container, and of an
-allocator-aware container (Table  [[tab:containers.allocatoraware]]). It
-provides the operations described in the preceding requirements table
-for equivalent keys; that is, an `unordered_multimap` supports the
-`a_eq` operations in that table, not the `a_uniq` operations. For an
-`unordered_multimap<Key, T>` the `key type` is `Key`, the mapped type is
-`T`, and the value type is `pair<const Key, T>`.
-This section only describes operations on `unordered_multimap` that are
-not described in one of the requirement tables, or for which there is
-additional semantic information.
 ``` cpp
 namespace std {
   template<class Key,
            class T,
            class Hash = hash<Key>,
            class Pred = equal_to<Key>,
            class Allocator = allocator<pair<const Key, T>>>
   class unordered_multimap {
   public:
-    // types:
     using key_type             = Key;
     using mapped_type          = T;
     using value_type           = pair<const Key, T>;
     using hasher               = Hash;
     using key_equal            = Pred;
@@ -5225,20 +5313,20 @@ namespace std {
                is_nothrow_move_assignable_v<Hash> &&
                is_nothrow_move_assignable_v<Pred>);
     unordered_multimap& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
-    // iterators:
     iterator       begin() noexcept;
     const_iterator begin() const noexcept;
     iterator       end() noexcept;
     const_iterator end() const noexcept;
     const_iterator cbegin() const noexcept;
     const_iterator cend() const noexcept;
-    // capacity:
-    bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
     // [unord.multimap.modifiers], modifiers
     template<class... Args> iterator emplace(Args&&... args);
@@ -5274,22 +5362,35 @@ namespace std {
     template<class H2, class P2>
       void merge(unordered_map<Key, T, H2, P2, Allocator>& source);
     template<class H2, class P2>
       void merge(unordered_map<Key, T, H2, P2, Allocator>&& source);
-    // observers:
     hasher hash_function() const;
     key_equal key_eq() const;
-    // map operations:
     iterator         find(const key_type& k);
     const_iterator   find(const key_type& k) const;
     size_type        count(const key_type& k) const;
     pair<iterator, iterator>               equal_range(const key_type& k);
     pair<const_iterator, const_iterator>   equal_range(const key_type& k) const;
-    // bucket interface:
     size_type bucket_count() const noexcept;
     size_type max_bucket_count() const noexcept;
     size_type bucket_size(size_type n) const;
     size_type bucket(const key_type& k) const;
     local_iterator begin(size_type n);
@@ -5306,66 +5407,59 @@ namespace std {
     void rehash(size_type n);
     void reserve(size_type n);
   };
   template<class InputIterator,
-           class Hash = hash<iter_key_t<InputIterator>>,
-           class Pred = equal_to<iter_key_t<InputIterator>>,
-           class Allocator = allocator<iter_to_alloc_t<InputIterator>>>
     unordered_multimap(InputIterator, InputIterator,
                        typename see below::size_type = see below,
                        Hash = Hash(), Pred = Pred(), Allocator = Allocator())
-      -> unordered_multimap<iter_key_t<InputIterator>, iter_value_t<InputIterator>, Hash, Pred,
-                            Allocator>;
   template<class Key, class T, class Hash = hash<Key>,
            class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>>
-    unordered_multimap(initializer_list<pair<const Key, T>>,
                        typename see below::size_type = see below,
                        Hash = Hash(), Pred = Pred(), Allocator = Allocator())
       -> unordered_multimap<Key, T, Hash, Pred, Allocator>;
   template<class InputIterator, class Allocator>
     unordered_multimap(InputIterator, InputIterator, typename see below::size_type, Allocator)
-      -> unordered_multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
-                            hash<iter_key_t<InputIterator>>,
-                            equal_to<iter_key_t<InputIterator>>, Allocator>;
   template<class InputIterator, class Allocator>
     unordered_multimap(InputIterator, InputIterator, Allocator)
-      -> unordered_multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
-                            hash<iter_key_t<InputIterator>>,
-                            equal_to<iter_key_t<InputIterator>>, Allocator>;
   template<class InputIterator, class Hash, class Allocator>
     unordered_multimap(InputIterator, InputIterator, typename see below::size_type, Hash,
                        Allocator)
-      -> unordered_multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>, Hash,
-                            equal_to<iter_key_t<InputIterator>>, Allocator>;
-  template<class Key, class T, typename Allocator>
-    unordered_multimap(initializer_list<pair<const Key, T>>, typename see below::size_type,
                        Allocator)
       -> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>;
-  template<class Key, class T, typename Allocator>
-    unordered_multimap(initializer_list<pair<const Key, T>>, Allocator)
       -> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>;
   template<class Key, class T, class Hash, class Allocator>
-    unordered_multimap(initializer_list<pair<const Key, T>>, typename see below::size_type,
                        Hash, Allocator)
       -> unordered_multimap<Key, T, Hash, equal_to<Key>, Allocator>;
- template <class Key, class T, class Hash, class Pred, class Alloc>
-    bool operator==(const unordered_multimap<Key, T, Hash, Pred, Alloc>& a,
-                    const unordered_multimap<Key, T, Hash, Pred, Alloc>& b);
-  template <class Key, class T, class Hash, class Pred, class Alloc>
-    bool operator!=(const unordered_multimap<Key, T, Hash, Pred, Alloc>& a,
-                    const unordered_multimap<Key, T, Hash, Pred, Alloc>& b);
-  // [unord.multimap.swap], swap
   template<class Key, class T, class Hash, class Pred, class Alloc>
     void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x,
               unordered_multimap<Key, T, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
 }
@@ -5373,11 +5467,11 @@ namespace std {
 A `size_type` parameter type in an `unordered_multimap` deduction guide
 refers to the `size_type` member type of the type deduced by the
 deduction guide.
-#### `unordered_multimap` constructors <a id="unord.multimap.cnstr">[[unord.multimap.cnstr]]</a>
 ``` cpp
 unordered_multimap() : unordered_multimap(size_type(see below)) { }
 explicit unordered_multimap(size_type n,
                             const hasher& hf = hasher(),
@@ -5413,76 +5507,85 @@ hash function, key equality predicate, and allocator, and using at least
 `l`) for the first form, or from the range \[`il.begin()`, `il.end()`)
 for the second form. `max_load_factor()` returns `1.0`.
 *Complexity:* Average case linear, worst case quadratic.
-#### `unordered_multimap` modifiers <a id="unord.multimap.modifiers">[[unord.multimap.modifiers]]</a>
 ``` cpp
 template<class P>
   iterator insert(P&& obj);
 ```
 *Effects:* Equivalent to: `return emplace(std::forward<P>(obj));`
-*Remarks:* This signature shall not participate in overload resolution
-unless `is_constructible_v<value_type, P&&>` is `true`.
 ``` cpp
 template<class P>
   iterator insert(const_iterator hint, P&& obj);
 ```
 *Effects:* Equivalent to:
 `return emplace_hint(hint, std::forward<P>(obj));`
-*Remarks:* This signature shall not participate in overload resolution
-unless `is_constructible_v<value_type, P&&>` is `true`.
-#### `unordered_multimap` swap <a id="unord.multimap.swap">[[unord.multimap.swap]]</a>
 ``` cpp
-template <class Key, class T, class Hash, class Pred, class Alloc>
- void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x,
- unordered_multimap<Key, T, Hash, Pred, Alloc>& y)
-    noexcept(noexcept(x.swap(y)));
 ```
-*Effects:* As if by `x.swap(y)`.
 ### Class template `unordered_set` <a id="unord.set">[[unord.set]]</a>
-#### Class template `unordered_set` overview <a id="unord.set.overview">[[unord.set.overview]]</a>
 An `unordered_set` is an unordered associative container that supports
 unique keys (an `unordered_set` contains at most one of each key value)
 and in which the elements’ keys are the elements themselves. The
 `unordered_set` class supports forward iterators.
-An `unordered_set` satisfies all of the requirements of a container, of
-an unordered associative container, and of an allocator-aware container
-(Table  [[tab:containers.allocatoraware]]). It provides the operations
-described in the preceding requirements table for unique keys; that is,
-an `unordered_set` supports the `a_uniq` operations in that table, not
-the `a_eq` operations. For an `unordered_set<Key>` the `key type` and
-the value type are both `Key`. The `iterator` and `const_iterator` types
-are both constant iterator types. It is unspecified whether they are the
 same type.
-This section only describes operations on `unordered_set` that are not
-described in one of the requirement tables, or for which there is
-additional semantic information.
 ``` cpp
 namespace std {
   template<class Key,
            class Hash = hash<Key>,
            class Pred = equal_to<Key>,
            class Allocator = allocator<Key>>
   class unordered_set {
   public:
-    // types:
     using key_type             = Key;
     using value_type           = Key;
     using hasher               = Hash;
     using key_equal            = Pred;
     using allocator_type       = Allocator;
@@ -5496,11 +5599,11 @@ namespace std {
     using iterator             = implementation-defined  // type of unordered_set::iterator; // see [container.requirements]
     using const_iterator       = implementation-defined  // type of unordered_set::const_iterator; // see [container.requirements]
     using local_iterator       = implementation-defined  // type of unordered_set::local_iterator; // see [container.requirements]
     using const_local_iterator = implementation-defined  // type of unordered_set::const_local_iterator; // see [container.requirements]
     using node_type            = unspecified;
-    using insert_return_type   = INSERT_RETURN_TYPE<iterator, node_type>;
     // [unord.set.cnstr], construct/copy/destroy
     unordered_set();
     explicit unordered_set(size_type n,
                            const hasher& hf = hasher(),
@@ -5545,24 +5648,24 @@ namespace std {
                is_nothrow_move_assignable_v<Hash> &&
                is_nothrow_move_assignable_v<Pred>);
     unordered_set& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
-    // iterators:
     iterator       begin() noexcept;
     const_iterator begin() const noexcept;
     iterator       end() noexcept;
     const_iterator end() const noexcept;
     const_iterator cbegin() const noexcept;
     const_iterator cend() const noexcept;
-    // capacity:
-    bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
-    // modifiers:
     template<class... Args> pair<iterator, bool> emplace(Args&&... args);
     template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
     pair<iterator, bool> insert(const value_type& obj);
     pair<iterator, bool> insert(value_type&& obj);
     iterator insert(const_iterator hint, const value_type& obj);
@@ -5592,22 +5695,35 @@ namespace std {
     template<class H2, class P2>
       void merge(unordered_multiset<Key, H2, P2, Allocator>& source);
     template<class H2, class P2>
       void merge(unordered_multiset<Key, H2, P2, Allocator>&& source);
-    // observers:
     hasher hash_function() const;
     key_equal key_eq() const;
-    // set operations:
     iterator         find(const key_type& k);
     const_iterator   find(const key_type& k) const;
     size_type        count(const key_type& k) const;
     pair<iterator, iterator>               equal_range(const key_type& k);
     pair<const_iterator, const_iterator>   equal_range(const key_type& k) const;
-    // bucket interface:
     size_type bucket_count() const noexcept;
     size_type max_bucket_count() const noexcept;
     size_type bucket_size(size_type n) const;
     size_type bucket(const key_type& k) const;
     local_iterator begin(size_type n);
@@ -5615,75 +5731,68 @@ namespace std {
     local_iterator end(size_type n);
     const_local_iterator end(size_type n) const;
     const_local_iterator cbegin(size_type n) const;
     const_local_iterator cend(size_type n) const;
-    // hash policy:
     float load_factor() const noexcept;
     float max_load_factor() const noexcept;
     void max_load_factor(float z);
     void rehash(size_type n);
     void reserve(size_type n);
   };
   template<class InputIterator,
-           class Hash = hash<typename iterator_traits<InputIterator>::value_type>,
-           class Pred = equal_to<typename iterator_traits<InputIterator>::value_type>,
-           class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
     unordered_set(InputIterator, InputIterator, typename see below::size_type = see below,
                   Hash = Hash(), Pred = Pred(), Allocator = Allocator())
-      -> unordered_set<typename iterator_traits<InputIterator>::value_type,
                        Hash, Pred, Allocator>;
   template<class T, class Hash = hash<T>,
            class Pred = equal_to<T>, class Allocator = allocator<T>>
     unordered_set(initializer_list<T>, typename see below::size_type = see below,
                   Hash = Hash(), Pred = Pred(), Allocator = Allocator())
       -> unordered_set<T, Hash, Pred, Allocator>;
   template<class InputIterator, class Allocator>
     unordered_set(InputIterator, InputIterator, typename see below::size_type, Allocator)
-      -> unordered_set<typename iterator_traits<InputIterator>::value_type,
-                       hash<typename iterator_traits<InputIterator>::value_type>,
-                       equal_to<typename iterator_traits<InputIterator>::value_type>,
                        Allocator>;
   template<class InputIterator, class Hash, class Allocator>
     unordered_set(InputIterator, InputIterator, typename see below::size_type,
                   Hash, Allocator)
-      -> unordered_set<typename iterator_traits<InputIterator>::value_type, Hash,
-                       equal_to<typename iterator_traits<InputIterator>::value_type>,
                        Allocator>;
   template<class T, class Allocator>
     unordered_set(initializer_list<T>, typename see below::size_type, Allocator)
       -> unordered_set<T, hash<T>, equal_to<T>, Allocator>;
   template<class T, class Hash, class Allocator>
     unordered_set(initializer_list<T>, typename see below::size_type, Hash, Allocator)
       -> unordered_set<T, Hash, equal_to<T>, Allocator>;
- template <class Key, class Hash, class Pred, class Alloc>
-    bool operator==(const unordered_set<Key, Hash, Pred, Alloc>& a,
-                    const unordered_set<Key, Hash, Pred, Alloc>& b);
-  template <class Key, class Hash, class Pred, class Alloc>
-    bool operator!=(const unordered_set<Key, Hash, Pred, Alloc>& a,
-                    const unordered_set<Key, Hash, Pred, Alloc>& b);
-  // [unord.set.swap], swap
   template<class Key, class Hash, class Pred, class Alloc>
     void swap(unordered_set<Key, Hash, Pred, Alloc>& x,
               unordered_set<Key, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
 A `size_type` parameter type in an `unordered_set` deduction guide
-refers to the `size_type` member type of the primary `unordered_set`
-template.
-#### `unordered_set` constructors <a id="unord.set.cnstr">[[unord.set.cnstr]]</a>
 ``` cpp
 unordered_set() : unordered_set(size_type(see below)) { }
 explicit unordered_set(size_type n,
                        const hasher& hf = hasher(),
@@ -5719,54 +5828,65 @@ buckets. If `n` is not provided, the number of buckets is
 `l`) for the first form, or from the range \[`il.begin()`, `il.end()`)
 for the second form. `max_load_factor()` returns `1.0`.
 *Complexity:* Average case linear, worst case quadratic.
-#### `unordered_set` swap <a id="unord.set.swap">[[unord.set.swap]]</a>
 ``` cpp
-template <class Key, class Hash, class Pred, class Alloc>
- void swap(unordered_set<Key, Hash, Pred, Alloc>& x,
- unordered_set<Key, Hash, Pred, Alloc>& y)
-    noexcept(noexcept(x.swap(y)));
 ```
-*Effects:* As if by `x.swap(y)`.
 ### Class template `unordered_multiset` <a id="unord.multiset">[[unord.multiset]]</a>
-#### Class template `unordered_multiset` overview <a id="unord.multiset.overview">[[unord.multiset.overview]]</a>
 An `unordered_multiset` is an unordered associative container that
 supports equivalent keys (an instance of `unordered_multiset` may
 contain multiple copies of the same key value) and in which each
 element’s key is the element itself. The `unordered_multiset` class
 supports forward iterators.
-An `unordered_multiset` satisfies all of the requirements of a
-container, of an unordered associative container, and of an
-allocator-aware container (Table  [[tab:containers.allocatoraware]]). It
-provides the operations described in the preceding requirements table
-for equivalent keys; that is, an `unordered_multiset` supports the
-`a_eq` operations in that table, not the `a_uniq` operations. For an
-`unordered_multiset<Key>` the `key type` and the value type are both
-`Key`. The `iterator` and `const_iterator` types are both constant
-iterator types. It is unspecified whether they are the same type.
-This section only describes operations on `unordered_multiset` that are
-not described in one of the requirement tables, or for which there is
-additional semantic information.
 ``` cpp
 namespace std {
   template<class Key,
            class Hash = hash<Key>,
            class Pred = equal_to<Key>,
            class Allocator = allocator<Key>>
   class unordered_multiset {
   public:
-    // types:
     using key_type             = Key;
     using value_type           = Key;
     using hasher               = Hash;
     using key_equal            = Pred;
     using allocator_type       = Allocator;
@@ -5828,24 +5948,24 @@ namespace std {
                is_nothrow_move_assignable_v<Hash> &&
                is_nothrow_move_assignable_v<Pred>);
     unordered_multiset& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
-    // iterators:
     iterator       begin() noexcept;
     const_iterator begin() const noexcept;
     iterator       end() noexcept;
     const_iterator end() const noexcept;
     const_iterator cbegin() const noexcept;
     const_iterator cend() const noexcept;
-    // capacity:
-    bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
-    // modifiers:
     template<class... Args> iterator emplace(Args&&... args);
     template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
     iterator insert(const value_type& obj);
     iterator insert(value_type&& obj);
     iterator insert(const_iterator hint, const value_type& obj);
@@ -5875,22 +5995,35 @@ namespace std {
     template<class H2, class P2>
       void merge(unordered_set<Key, H2, P2, Allocator>& source);
     template<class H2, class P2>
       void merge(unordered_set<Key, H2, P2, Allocator>&& source);
-    // observers:
     hasher hash_function() const;
     key_equal key_eq() const;
-    // set operations:
     iterator         find(const key_type& k);
     const_iterator   find(const key_type& k) const;
     size_type        count(const key_type& k) const;
     pair<iterator, iterator>               equal_range(const key_type& k);
     pair<const_iterator, const_iterator>   equal_range(const key_type& k) const;
-    // bucket interface:
     size_type bucket_count() const noexcept;
     size_type max_bucket_count() const noexcept;
     size_type bucket_size(size_type n) const;
     size_type bucket(const key_type& k) const;
     local_iterator begin(size_type n);
@@ -5898,75 +6031,68 @@ namespace std {
     local_iterator end(size_type n);
     const_local_iterator end(size_type n) const;
     const_local_iterator cbegin(size_type n) const;
     const_local_iterator cend(size_type n) const;
-    // hash policy:
     float load_factor() const noexcept;
     float max_load_factor() const noexcept;
     void max_load_factor(float z);
     void rehash(size_type n);
     void reserve(size_type n);
   };
   template<class InputIterator,
-           class Hash = hash<typename iterator_traits<InputIterator>::value_type>,
-           class Pred = equal_to<typename iterator_traits<InputIterator>::value_type>,
-           class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
     unordered_multiset(InputIterator, InputIterator, see below::size_type = see below,
                        Hash = Hash(), Pred = Pred(), Allocator = Allocator())
-      -> unordered_multiset<typename iterator_traits<InputIterator>::value_type,
                             Hash, Pred, Allocator>;
   template<class T, class Hash = hash<T>,
            class Pred = equal_to<T>, class Allocator = allocator<T>>
     unordered_multiset(initializer_list<T>, typename see below::size_type = see below,
                        Hash = Hash(), Pred = Pred(), Allocator = Allocator())
       -> unordered_multiset<T, Hash, Pred, Allocator>;
   template<class InputIterator, class Allocator>
     unordered_multiset(InputIterator, InputIterator, typename see below::size_type, Allocator)
-      -> unordered_multiset<typename iterator_traits<InputIterator>::value_type,
-                            hash<typename iterator_traits<InputIterator>::value_type>,
-                            equal_to<typename iterator_traits<InputIterator>::value_type>,
                             Allocator>;
   template<class InputIterator, class Hash, class Allocator>
     unordered_multiset(InputIterator, InputIterator, typename see below::size_type,
                        Hash, Allocator)
-      -> unordered_multiset<typename iterator_traits<InputIterator>::value_type, Hash,
-                            equal_to<typename iterator_traits<InputIterator>::value_type>,
                             Allocator>;
   template<class T, class Allocator>
     unordered_multiset(initializer_list<T>, typename see below::size_type, Allocator)
       -> unordered_multiset<T, hash<T>, equal_to<T>, Allocator>;
   template<class T, class Hash, class Allocator>
     unordered_multiset(initializer_list<T>, typename see below::size_type, Hash, Allocator)
       -> unordered_multiset<T, Hash, equal_to<T>, Allocator>;
- template <class Key, class Hash, class Pred, class Alloc>
-    bool operator==(const unordered_multiset<Key, Hash, Pred, Alloc>& a,
-                    const unordered_multiset<Key, Hash, Pred, Alloc>& b);
-  template <class Key, class Hash, class Pred, class Alloc>
-    bool operator!=(const unordered_multiset<Key, Hash, Pred, Alloc>& a,
-                    const unordered_multiset<Key, Hash, Pred, Alloc>& b);
-  // [unord.multiset.swap], swap
   template<class Key, class Hash, class Pred, class Alloc>
     void swap(unordered_multiset<Key, Hash, Pred, Alloc>& x,
               unordered_multiset<Key, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
 A `size_type` parameter type in an `unordered_multiset` deduction guide
-refers to the `size_type` member type of the primary
-`unordered_multiset` template.
-#### `unordered_multiset` constructors <a id="unord.multiset.cnstr">[[unord.multiset.cnstr]]</a>
 ``` cpp
 unordered_multiset() : unordered_multiset(size_type(see below)) { }
 explicit unordered_multiset(size_type n,
                             const hasher& hf = hasher(),
@@ -6002,20 +6128,31 @@ hash function, key equality predicate, and allocator, and using at least
 `l`) for the first form, or from the range \[`il.begin()`, `il.end()`)
 for the second form. `max_load_factor()` returns `1.0`.
 *Complexity:* Average case linear, worst case quadratic.
-#### `unordered_multiset` swap <a id="unord.multiset.swap">[[unord.multiset.swap]]</a>
 ``` cpp
-template <class Key, class Hash, class Pred, class Alloc>
- void swap(unordered_multiset<Key, Hash, Pred, Alloc>& x,
- unordered_multiset<Key, Hash, Pred, Alloc>& y)
-    noexcept(noexcept(x.swap(y)));
 ```
-*Effects:* As if by `x.swap(y)`.
 ## Container adaptors <a id="container.adaptors">[[container.adaptors]]</a>
 ### In general <a id="container.adaptors.general">[[container.adaptors.general]]</a>
@@ -6050,70 +6187,88 @@ overload resolution if any of the following are true:
   `uses_allocator_v<Container, Allocator>` is `false`.
 ### Header `<queue>` synopsis <a id="queue.syn">[[queue.syn]]</a>
 ``` cpp
-#include <initializer_list>
 namespace std {
   template<class T, class Container = deque<T>> class queue;
   template<class T, class Container = vector<T>,
            class Compare = less<typename Container::value_type>>
     class priority_queue;
-  template <class T, class Container>
-    bool operator==(const queue<T, Container>& x, const queue<T, Container>& y);
-  template <class T, class Container>
-    bool operator< (const queue<T, Container>& x, const queue<T, Container>& y);
-  template <class T, class Container>
-    bool operator!=(const queue<T, Container>& x, const queue<T, Container>& y);
-  template <class T, class Container>
-    bool operator> (const queue<T, Container>& x, const queue<T, Container>& y);
-  template <class T, class Container>
-    bool operator>=(const queue<T, Container>& x, const queue<T, Container>& y);
-  template <class T, class Container>
-    bool operator<=(const queue<T, Container>& x, const queue<T, Container>& y);
-  template <class T, class Container>
-    void swap(queue<T, Container>& x, queue<T, Container>& y) noexcept(noexcept(x.swap(y)));
   template<class T, class Container, class Compare>
     void swap(priority_queue<T, Container, Compare>& x,
               priority_queue<T, Container, Compare>& y) noexcept(noexcept(x.swap(y)));
 }
 ```
 ### Header `<stack>` synopsis <a id="stack.syn">[[stack.syn]]</a>
 ``` cpp
-#include <initializer_list>
 namespace std {
   template<class T, class Container = deque<T>> class stack;
   template<class T, class Container>
     bool operator==(const stack<T, Container>& x, const stack<T, Container>& y);
-  template <class T, class Container>
-    bool operator< (const stack<T, Container>& x, const stack<T, Container>& y);
   template<class T, class Container>
     bool operator!=(const stack<T, Container>& x, const stack<T, Container>& y);
   template<class T, class Container>
     bool operator> (const stack<T, Container>& x, const stack<T, Container>& y);
-  template <class T, class Container>
-    bool operator>=(const stack<T, Container>& x, const stack<T, Container>& y);
   template<class T, class Container>
     bool operator<=(const stack<T, Container>& x, const stack<T, Container>& y);
   template<class T, class Container>
     void swap(stack<T, Container>& x, stack<T, Container>& y) noexcept(noexcept(x.swap(y)));
 }
 ```
 ### Class template `queue` <a id="queue">[[queue]]</a>
-#### `queue` definition <a id="queue.defn">[[queue.defn]]</a>
 Any sequence container supporting operations `front()`, `back()`,
 `push_back()` and `pop_front()` can be used to instantiate `queue`. In
-particular, `list` ([[list]]) and `deque` ([[deque]]) can be used.
 ``` cpp
 namespace std {
   template<class T, class Container = deque<T>>
   class queue {
@@ -6126,28 +6281,30 @@ namespace std {
   protected:
     Container c;
   public:
     explicit queue(const Container&);
-    explicit queue(Container&& = Container());
     template<class Alloc> explicit queue(const Alloc&);
     template<class Alloc> queue(const Container&, const Alloc&);
     template<class Alloc> queue(Container&&, const Alloc&);
     template<class Alloc> queue(const queue&, const Alloc&);
     template<class Alloc> queue(queue&&, const Alloc&);
-    bool empty() const { return c.empty(); }
     size_type         size()  const     { return c.size(); }
     reference         front()           { return c.front(); }
     const_reference   front() const     { return c.front(); }
     reference         back()            { return c.back(); }
     const_reference   back() const      { return c.back(); }
     void push(const value_type& x)      { c.push_back(x); }
     void push(value_type&& x)           { c.push_back(std::move(x)); }
     template<class... Args>
- reference emplace(Args&&... args) { return c.emplace_back(std::forward<Args>(args)...); }
     void pop()                          { c.pop_front(); }
     void swap(queue& q) noexcept(is_nothrow_swappable_v<Container>)
       { using std::swap; swap(c, q.c); }
   };
@@ -6155,86 +6312,73 @@ namespace std {
     queue(Container) -> queue<typename Container::value_type, Container>;
   template<class Container, class Allocator>
     queue(Container, Allocator) -> queue<typename Container::value_type, Container>;
-  template <class T, class Container>
-    bool operator==(const queue<T, Container>& x, const queue<T, Container>& y);
-  template <class T, class Container>
-    bool operator< (const queue<T, Container>& x, const queue<T, Container>& y);
-  template <class T, class Container>
-    bool operator!=(const queue<T, Container>& x, const queue<T, Container>& y);
-  template <class T, class Container>
-    bool operator> (const queue<T, Container>& x, const queue<T, Container>& y);
-  template <class T, class Container>
-    bool operator>=(const queue<T, Container>& x, const queue<T, Container>& y);
-  template <class T, class Container>
-    bool operator<=(const queue<T, Container>& x, const queue<T, Container>& y);
   template<class T, class Container>
     void swap(queue<T, Container>& x, queue<T, Container>& y) noexcept(noexcept(x.swap(y)));
   template<class T, class Container, class Alloc>
     struct uses_allocator<queue<T, Container>, Alloc>
       : uses_allocator<Container, Alloc>::type { };
 }
 ```
-#### `queue` constructors <a id="queue.cons">[[queue.cons]]</a>
 ``` cpp
 explicit queue(const Container& cont);
 ```
-*Effects:*  Initializes `c` with `cont`.
 ``` cpp
-explicit queue(Container&& cont = Container());
 ```
-*Effects:*  Initializes `c` with `std::move(cont)`.
-#### `queue` constructors with allocators <a id="queue.cons.alloc">[[queue.cons.alloc]]</a>
 If `uses_allocator_v<container_type, Alloc>` is `false` the constructors
 in this subclause shall not participate in overload resolution.
 ``` cpp
 template<class Alloc> explicit queue(const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `a`.
 ``` cpp
 template<class Alloc> queue(const container_type& cont, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `cont` as the first argument and `a` as
 the second argument.
 ``` cpp
 template<class Alloc> queue(container_type&& cont, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `std::move(cont)` as the first argument
 and `a` as the second argument.
 ``` cpp
 template<class Alloc> queue(const queue& q, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `q.c` as the first argument and `a` as
 the second argument.
 ``` cpp
 template<class Alloc> queue(queue&& q, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `std::move(q.c)` as the first argument
 and `a` as the second argument.
-#### `queue` operators <a id="queue.ops">[[queue.ops]]</a>
 ``` cpp
 template<class T, class Container>
   bool operator==(const queue<T, Container>& x, const queue<T, Container>& y);
 ```
@@ -6253,53 +6397,62 @@ template <class T, class Container>
   bool operator< (const queue<T, Container>& x, const queue<T, Container>& y);
 ```
 *Returns:* `x.c < y.c`.
-``` cpp
-template <class T, class Container>
-  bool operator<=(const queue<T, Container>& x, const queue<T, Container>& y);
-```
-*Returns:* `x.c <= y.c`.
 ``` cpp
 template<class T, class Container>
   bool operator> (const queue<T, Container>& x, const queue<T, Container>& y);
 ```
 *Returns:* `x.c > y.c`.
 ``` cpp
 template<class T, class Container>
     bool operator>=(const queue<T, Container>& x,
                     const queue<T, Container>& y);
 ```
 *Returns:* `x.c >= y.c`.
-#### `queue` specialized algorithms <a id="queue.special">[[queue.special]]</a>
 ``` cpp
 template<class T, class Container>
   void swap(queue<T, Container>& x, queue<T, Container>& y) noexcept(noexcept(x.swap(y)));
 ```
-*Remarks:* This function shall not participate in overload resolution
-unless `is_swappable_v<Container>` is `true`.
 *Effects:* As if by `x.swap(y)`.
 ### Class template `priority_queue` <a id="priority.queue">[[priority.queue]]</a>
 Any sequence container with random access iterator and supporting
 operations `front()`, `push_back()` and `pop_back()` can be used to
-instantiate `priority_queue`. In particular, `vector` ([[vector]]) and
-`deque` ([[deque]]) can be used. Instantiating `priority_queue` also
 involves supplying a function or function object for making priority
 comparisons; the library assumes that the function or function object
-defines a strict weak ordering ([[alg.sorting]]).
 ``` cpp
 namespace std {
   template<class T, class Container = vector<T>,
            class Compare = less<typename Container::value_type>>
@@ -6315,26 +6468,28 @@ namespace std {
   protected:
     Container c;
     Compare comp;
   public:
     priority_queue(const Compare& x, const Container&);
- explicit priority_queue(const Compare& x = Compare(), Container&& = Container());
     template<class InputIterator>
-      priority_queue(InputIterator first, InputIterator last,
- const Compare& x, const Container&);
     template<class InputIterator>
       priority_queue(InputIterator first, InputIterator last,
                      const Compare& x = Compare(), Container&& = Container());
     template<class Alloc> explicit priority_queue(const Alloc&);
     template<class Alloc> priority_queue(const Compare&, const Alloc&);
     template<class Alloc> priority_queue(const Compare&, const Container&, const Alloc&);
     template<class Alloc> priority_queue(const Compare&, Container&&, const Alloc&);
     template<class Alloc> priority_queue(const priority_queue&, const Alloc&);
     template<class Alloc> priority_queue(priority_queue&&, const Alloc&);
-    bool empty() const { return c.empty(); }
     size_type size()  const          { return c.size(); }
     const_reference   top() const    { return c.front(); }
     void push(const value_type& x);
     void push(value_type&& x);
     template<class... Args> void emplace(Args&&... args);
@@ -6368,93 +6523,90 @@ namespace std {
     struct uses_allocator<priority_queue<T, Container, Compare>, Alloc>
       : uses_allocator<Container, Alloc>::type { };
 }
 ```
-#### `priority_queue` constructors <a id="priqueue.cons">[[priqueue.cons]]</a>
 ``` cpp
 priority_queue(const Compare& x, const Container& y);
-explicit priority_queue(const Compare& x = Compare(), Container&& y = Container());
 ```
-*Requires:* `x` shall define a strict weak ordering ([[alg.sorting]]).
 *Effects:* Initializes `comp` with `x` and `c` with `y` (copy
 constructing or move constructing as appropriate); calls
 `make_heap(c.begin(), c.end(), comp)`.
 ``` cpp
 template<class InputIterator>
-  priority_queue(InputIterator first, InputIterator last,
-                 const Compare& x,
-                 const Container& y);
 template<class InputIterator>
-  priority_queue(InputIterator first, InputIterator last,
-                 const Compare& x = Compare(),
                  Container&& y = Container());
 ```
-*Requires:* `x` shall define a strict weak ordering ([[alg.sorting]]).
 *Effects:* Initializes `comp` with `x` and `c` with `y` (copy
 constructing or move constructing as appropriate); calls
 `c.insert(c.end(), first, last)`; and finally calls
 `make_heap(c.begin(), c.end(), comp)`.
-#### `priority_queue` constructors with allocators <a id="priqueue.cons.alloc">[[priqueue.cons.alloc]]</a>
 If `uses_allocator_v<container_type, Alloc>` is `false` the constructors
 in this subclause shall not participate in overload resolution.
 ``` cpp
 template<class Alloc> explicit priority_queue(const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `a` and value-initializes `comp`.
 ``` cpp
 template<class Alloc> priority_queue(const Compare& compare, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `a` and initializes `comp` with
 `compare`.
 ``` cpp
 template<class Alloc>
   priority_queue(const Compare& compare, const Container& cont, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `cont` as the first argument and `a` as
 the second argument, and initializes `comp` with `compare`; calls
 `make_heap(c.begin(), c.end(), comp)`.
 ``` cpp
 template<class Alloc>
   priority_queue(const Compare& compare, Container&& cont, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `std::move(cont)` as the first argument
 and `a` as the second argument, and initializes `comp` with `compare`;
 calls `make_heap(c.begin(), c.end(), comp)`.
 ``` cpp
 template<class Alloc> priority_queue(const priority_queue& q, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `q.c` as the first argument and `a` as
 the second argument, and initializes `comp` with `q.comp`.
 ``` cpp
 template<class Alloc> priority_queue(priority_queue&& q, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `std::move(q.c)` as the first argument
 and `a` as the second argument, and initializes `comp` with
 `std::move(q.comp)`.
-#### `priority_queue` members <a id="priqueue.members">[[priqueue.members]]</a>
 ``` cpp
 void push(const value_type& x);
 ```
@@ -6475,11 +6627,11 @@ void push(value_type&& x);
 c.push_back(std::move(x));
 push_heap(c.begin(), c.end(), comp);
 ```
 ``` cpp
-template <class... Args> void emplace(Args&&... args)
 ```
 *Effects:* As if by:
 ``` cpp
@@ -6496,32 +6648,30 @@ void pop();
 ``` cpp
 pop_heap(c.begin(), c.end(), comp);
 c.pop_back();
 ```
-#### `priority_queue` specialized algorithms <a id="priqueue.special">[[priqueue.special]]</a>
 ``` cpp
 template<class T, class Container, class Compare>
   void swap(priority_queue<T, Container, Compare>& x,
             priority_queue<T, Container, Compare>& y) noexcept(noexcept(x.swap(y)));
 ```
-*Remarks:* This function shall not participate in overload resolution
-unless `is_swappable_v<Container>` is `true` and
 `is_swappable_v<Compare>` is `true`.
 *Effects:* As if by `x.swap(y)`.
 ### Class template `stack` <a id="stack">[[stack]]</a>
 Any sequence container supporting operations `back()`, `push_back()` and
-`pop_back()` can be used to instantiate `stack`. In particular,
-`vector` ([[vector]]), `list` ([[list]]) and `deque` ([[deque]]) can
-be used.
-#### `stack` definition <a id="stack.defn">[[stack.defn]]</a>
 ``` cpp
 namespace std {
   template<class T, class Container = deque<T>>
   class stack {
@@ -6534,26 +6684,28 @@ namespace std {
   protected:
     Container c;
   public:
     explicit stack(const Container&);
-    explicit stack(Container&& = Container());
     template<class Alloc> explicit stack(const Alloc&);
     template<class Alloc> stack(const Container&, const Alloc&);
     template<class Alloc> stack(Container&&, const Alloc&);
     template<class Alloc> stack(const stack&, const Alloc&);
     template<class Alloc> stack(stack&&, const Alloc&);
-    bool empty() const { return c.empty(); }
     size_type size()  const             { return c.size(); }
     reference         top()             { return c.back(); }
     const_reference   top() const       { return c.back(); }
     void push(const value_type& x)      { c.push_back(x); }
     void push(value_type&& x)           { c.push_back(std::move(x)); }
     template<class... Args>
- reference emplace(Args&&... args) { return c.emplace_back(std::forward<Args>(args)...); }
     void pop()                          { c.pop_back(); }
     void swap(stack& s) noexcept(is_nothrow_swappable_v<Container>)
       { using std::swap; swap(c, s.c); }
   };
@@ -6561,85 +6713,70 @@ namespace std {
     stack(Container) -> stack<typename Container::value_type, Container>;
   template<class Container, class Allocator>
     stack(Container, Allocator) -> stack<typename Container::value_type, Container>;
-  template <class T, class Container>
-    bool operator==(const stack<T, Container>& x, const stack<T, Container>& y);
-  template <class T, class Container>
-    bool operator< (const stack<T, Container>& x, const stack<T, Container>& y);
-  template <class T, class Container>
-    bool operator!=(const stack<T, Container>& x, const stack<T, Container>& y);
-  template <class T, class Container>
-    bool operator> (const stack<T, Container>& x, const stack<T, Container>& y);
-  template <class T, class Container>
-    bool operator>=(const stack<T, Container>& x, const stack<T, Container>& y);
-  template <class T, class Container>
-    bool operator<=(const stack<T, Container>& x, const stack<T, Container>& y);
-  template <class T, class Container>
-    void swap(stack<T, Container>& x, stack<T, Container>& y) noexcept(noexcept(x.swap(y)));
   template<class T, class Container, class Alloc>
     struct uses_allocator<stack<T, Container>, Alloc>
       : uses_allocator<Container, Alloc>::type { };
 }
 ```
-#### `stack` constructors <a id="stack.cons">[[stack.cons]]</a>
 ``` cpp
 explicit stack(const Container& cont);
 ```
 *Effects:* Initializes `c` with `cont`.
 ``` cpp
-explicit stack(Container&& cont = Container());
 ```
 *Effects:* Initializes `c` with `std::move(cont)`.
-#### `stack` constructors with allocators <a id="stack.cons.alloc">[[stack.cons.alloc]]</a>
 If `uses_allocator_v<container_type, Alloc>` is `false` the constructors
 in this subclause shall not participate in overload resolution.
 ``` cpp
 template<class Alloc> explicit stack(const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `a`.
 ``` cpp
 template<class Alloc> stack(const container_type& cont, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `cont` as the first argument and `a` as
 the second argument.
 ``` cpp
 template<class Alloc> stack(container_type&& cont, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `std::move(cont)` as the first argument
 and `a` as the second argument.
 ``` cpp
 template<class Alloc> stack(const stack& s, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `s.c` as the first argument and `a` as
 the second argument.
 ``` cpp
 template<class Alloc> stack(stack&& s, const Alloc& a);
 ```
-*Effects:*  Initializes `c` with `std::move(s.c)` as the first argument
 and `a` as the second argument.
-#### `stack` operators <a id="stack.ops">[[stack.ops]]</a>
 ``` cpp
 template<class T, class Container>
   bool operator==(const stack<T, Container>& x, const stack<T, Container>& y);
 ```
@@ -6658,133 +6795,660 @@ template <class T, class Container>
   bool operator< (const stack<T, Container>& x, const stack<T, Container>& y);
 ```
 *Returns:* `x.c < y.c`.
-``` cpp
-template <class T, class Container>
-  bool operator<=(const stack<T, Container>& x, const stack<T, Container>& y);
-```
-*Returns:* `x.c <= y.c`.
 ``` cpp
 template<class T, class Container>
   bool operator> (const stack<T, Container>& x, const stack<T, Container>& y);
 ```
 *Returns:* `x.c > y.c`.
 ``` cpp
 template<class T, class Container>
     bool operator>=(const stack<T, Container>& x, const stack<T, Container>& y);
 ```
 *Returns:* `x.c >= y.c`.
-#### `stack` specialized algorithms <a id="stack.special">[[stack.special]]</a>
 ``` cpp
 template<class T, class Container>
   void swap(stack<T, Container>& x, stack<T, Container>& y) noexcept(noexcept(x.swap(y)));
 ```
-*Remarks:* This function shall not participate in overload resolution
-unless `is_swappable_v<Container>` is `true`.
 *Effects:* As if by `x.swap(y)`.
 <!-- Link reference definitions -->
 [alg.sorting]: algorithms.md#alg.sorting
 [algorithm.stable]: library.md#algorithm.stable
 [algorithms]: algorithms.md#algorithms
 [allocator.requirements]: library.md#allocator.requirements
 [allocator.requirements.completeness]: library.md#allocator.requirements.completeness
 [allocator.traits.members]: utilities.md#allocator.traits.members
 [array]: #array
 [array.cons]: #array.cons
-[array.data]: #array.data
-[array.fill]: #array.fill
 [array.overview]: #array.overview
-[array.size]: #array.size
 [array.special]: #array.special
-[array.swap]: #array.swap
 [array.syn]: #array.syn
 [array.tuple]: #array.tuple
 [array.zero]: #array.zero
 [associative]: #associative
 [associative.general]: #associative.general
 [associative.map.syn]: #associative.map.syn
 [associative.reqmts]: #associative.reqmts
 [associative.reqmts.except]: #associative.reqmts.except
 [associative.set.syn]: #associative.set.syn
 [basic.string]: strings.md#basic.string
-[class.copy]: special.md#class.copy
-[class.ctor]: special.md#class.ctor
-[class.dtor]: special.md#class.dtor
 [container.adaptors]: #container.adaptors
 [container.adaptors.general]: #container.adaptors.general
 [container.insert.return]: #container.insert.return
 [container.node]: #container.node
 [container.node.cons]: #container.node.cons
 [container.node.dtor]: #container.node.dtor
 [container.node.modifiers]: #container.node.modifiers
 [container.node.observers]: #container.node.observers
 [container.node.overview]: #container.node.overview
 [container.requirements]: #container.requirements
 [container.requirements.dataraces]: #container.requirements.dataraces
 [container.requirements.general]: #container.requirements.general
 [containers]: #containers
 [containers.general]: #containers.general
 [dcl.init.aggr]: dcl.md#dcl.init.aggr
 [deque]: #deque
 [deque.capacity]: #deque.capacity
 [deque.cons]: #deque.cons
 [deque.modifiers]: #deque.modifiers
 [deque.overview]: #deque.overview
-[deque.special]: #deque.special
 [deque.syn]: #deque.syn
-[forward.iterators]: iterators.md#forward.iterators
-[forward_list.syn]: #forward_list.syn
 [forwardlist]: #forwardlist
 [forwardlist.access]: #forwardlist.access
 [forwardlist.cons]: #forwardlist.cons
 [forwardlist.iter]: #forwardlist.iter
 [forwardlist.modifiers]: #forwardlist.modifiers
 [forwardlist.ops]: #forwardlist.ops
 [forwardlist.overview]: #forwardlist.overview
-[forwardlist.spec]: #forwardlist.spec
 [hash.requirements]: library.md#hash.requirements
 [iterator.requirements]: iterators.md#iterator.requirements
 [iterator.requirements.general]: iterators.md#iterator.requirements.general
 [list]: #list
 [list.capacity]: #list.capacity
 [list.cons]: #list.cons
 [list.modifiers]: #list.modifiers
 [list.ops]: #list.ops
 [list.overview]: #list.overview
-[list.special]: #list.special
 [list.syn]: #list.syn
 [map]: #map
 [map.access]: #map.access
 [map.cons]: #map.cons
 [map.modifiers]: #map.modifiers
 [map.overview]: #map.overview
-[map.special]: #map.special
 [multimap]: #multimap
 [multimap.cons]: #multimap.cons
 [multimap.modifiers]: #multimap.modifiers
 [multimap.overview]: #multimap.overview
-[multimap.special]: #multimap.special
 [multiset]: #multiset
 [multiset.cons]: #multiset.cons
 [multiset.overview]: #multiset.overview
-[multiset.special]: #multiset.special
 [priority.queue]: #priority.queue
 [priqueue.cons]: #priqueue.cons
 [priqueue.cons.alloc]: #priqueue.cons.alloc
 [priqueue.members]: #priqueue.members
 [priqueue.special]: #priqueue.special
 [queue]: #queue
 [queue.cons]: #queue.cons
 [queue.cons.alloc]: #queue.cons.alloc
 [queue.defn]: #queue.defn
@@ -6796,67 +7460,76 @@ unless `is_swappable_v<Container>` is `true`.
 [sequence.reqmts]: #sequence.reqmts
 [sequences]: #sequences
 [sequences.general]: #sequences.general
 [set]: #set
 [set.cons]: #set.cons
 [set.overview]: #set.overview
-[set.special]: #set.special
 [stack]: #stack
 [stack.cons]: #stack.cons
 [stack.cons.alloc]: #stack.cons.alloc
 [stack.defn]: #stack.defn
 [stack.ops]: #stack.ops
 [stack.special]: #stack.special
 [stack.syn]: #stack.syn
 [strings]: strings.md#strings
 [swappable.requirements]: library.md#swappable.requirements
-[tab:HashRequirements]: #tab:HashRequirements
-[tab:containers.allocatoraware]: #tab:containers.allocatoraware
-[tab:containers.associative.requirements]: #tab:containers.associative.requirements
-[tab:containers.container.requirements]: #tab:containers.container.requirements
-[tab:containers.lib.summary]: #tab:containers.lib.summary
-[tab:containers.node.compat]: #tab:containers.node.compat
-[tab:containers.optional.operations]: #tab:containers.optional.operations
-[tab:containers.reversible.requirements]: #tab:containers.reversible.requirements
-[tab:containers.sequence.optional]: #tab:containers.sequence.optional
-[tab:containers.sequence.requirements]: #tab:containers.sequence.requirements
 [temp.deduct]: temp.md#temp.deduct
 [unord]: #unord
 [unord.general]: #unord.general
 [unord.hash]: utilities.md#unord.hash
 [unord.map]: #unord.map
 [unord.map.cnstr]: #unord.map.cnstr
 [unord.map.elem]: #unord.map.elem
 [unord.map.modifiers]: #unord.map.modifiers
 [unord.map.overview]: #unord.map.overview
-[unord.map.swap]: #unord.map.swap
 [unord.map.syn]: #unord.map.syn
 [unord.multimap]: #unord.multimap
 [unord.multimap.cnstr]: #unord.multimap.cnstr
 [unord.multimap.modifiers]: #unord.multimap.modifiers
 [unord.multimap.overview]: #unord.multimap.overview
-[unord.multimap.swap]: #unord.multimap.swap
 [unord.multiset]: #unord.multiset
 [unord.multiset.cnstr]: #unord.multiset.cnstr
 [unord.multiset.overview]: #unord.multiset.overview
-[unord.multiset.swap]: #unord.multiset.swap
 [unord.req]: #unord.req
 [unord.req.except]: #unord.req.except
 [unord.set]: #unord.set
 [unord.set.cnstr]: #unord.set.cnstr
 [unord.set.overview]: #unord.set.overview
-[unord.set.swap]: #unord.set.swap
 [unord.set.syn]: #unord.set.syn
 [vector]: #vector
 [vector.bool]: #vector.bool
 [vector.capacity]: #vector.capacity
 [vector.cons]: #vector.cons
 [vector.data]: #vector.data
 [vector.modifiers]: #vector.modifiers
 [vector.overview]: #vector.overview
-[vector.special]: #vector.special
 [vector.syn]: #vector.syn
 [^1]: Equality comparison is a refinement of partitioning if no two
     objects that compare equal fall into different partitions.
 [^2]: These member functions are only provided by containers whose

 This Clause describes components that C++ programs may use to organize
 collections of information.
 The following subclauses describe container requirements, and components
 for sequence containers and associative containers, as summarized in
+[[containers.summary]].
+**Table: Containers library summary** <a id="containers.summary">[containers.summary]</a>
 | Subclause                  |                                  | Header                                                       |
+| -------------------------- | -------------------------------- | ------------------------------------------------------------ |
 | [[container.requirements]] | Requirements                     |                                                              |
+| [[sequences]]              | Sequence containers              | `<array>`, `<deque>`, `<forward_list>`, `<list>`, `<vector>` |
+| [[associative]]            | Associative containers           | `<map>`, `<set>`                                             |
+| [[unord]]                  | Unordered associative containers | `<unordered_map>`, `<unordered_set>`                         |
+| [[container.adaptors]]     | Container adaptors               | `<queue>`, `<stack>`                                         |
+| [[views]]                  | Views                            | `<span>` |
 ## Container requirements <a id="container.requirements">[[container.requirements]]</a>
 ### General container requirements <a id="container.requirements.general">[[container.requirements.general]]</a>
 For the components affected by this subclause that declare an
 `allocator_type`, objects stored in these components shall be
 constructed using the function
 `allocator_traits<allocator_type>::rebind_traits<U>::{}construct` and
 destroyed using the function
+`allocator_traits<allocator_type>::rebind_traits<U>::{}destroy`
+[[allocator.traits.members]], where `U` is either
 `allocator_type::value_type` or an internal type used by the container.
 These functions are called only for the container’s element type, not
 for internal types used by the container.
 [*Note 1*: This means, for example, that a node-based container might
 need to construct nodes containing aligned buffers and call `construct`
 to place the element into the buffer. — *end note*]
+In Tables  [[tab:container.req]], [[tab:container.rev.req]], and
+[[tab:container.opt]] `X` denotes a container class containing objects
+of type `T`, `a` and `b` denote values of type `X`, `i` and `j` denote
+values of type (possibly const) `X::iterator`, `u` denotes an
+identifier, `r` denotes a non-const value of type `X`, and `rv` denotes
+a non-const rvalue of type `X`.
 Those entries marked “(Note A)” or “(Note B)” have linear complexity for
 `array` and have constant complexity for all other standard containers.
+[*Note 2*: The algorithm `equal()` is defined in
 [[algorithms]]. — *end note*]
 The member function `size()` returns the number of elements in the
 container. The number of elements is defined by the rules of
 constructors, inserts, and erases.
 i != j
 i < j
 i <= j
 i >= j
 i > j
+i <=> j
 i - j
 ```
 where `i` and `j` denote objects of a container’s `iterator` type,
 either or both may be replaced by an object of the container’s
 belonging to the container being moved. Such move construction of the
 allocator shall not exit via an exception. All other constructors for
 these container types take a `const allocator_type&` argument.
 [*Note 4*: If an invocation of a constructor uses the default value of
+an optional allocator argument, then the allocator type must support
 value-initialization. — *end note*]
 A copy of this allocator is used for any memory allocation and element
 construction performed, by these constructors and by all member
 functions, during the lifetime of each container object or until the
 in the other container after the swap. It is unspecified whether an
 iterator with value `a.end()` before the swap will have value `b.end()`
 after the swap.
 If the iterator type of a container belongs to the bidirectional or
+random access iterator categories [[iterator.requirements]], the
+container is called *reversible* and meets the additional requirements
+in [[container.rev.req]].
 Unless otherwise specified (see  [[associative.reqmts.except]],
 [[unord.req.except]], [[deque.modifiers]], and [[vector.modifiers]]) all
 container types defined in this Clause meet the following additional
 requirements:
 in terms of other functions), invoking a container member function or
 passing a container as an argument to a library function shall not
 invalidate iterators to, or change the values of, objects within that
 container.
+A *contiguous container* is a container whose member types `iterator`
+and `const_iterator` meet the *Cpp17RandomAccessIterator* requirements
+[[random.access.iterators]] and model `contiguous_iterator`
+[[iterator.concept.contiguous]].
+[[container.opt]] lists operations that are provided for some types of
+containers but not others. Those containers for which the listed
+operations are provided shall implement the semantics described in
+[[container.opt]] unless otherwise stated. If the iterators passed to
+`lexicographical_compare_three_way` meet the constexpr iterator
+requirements [[iterator.requirements.general]] then the operations
+described in [[container.opt]] are implemented by constexpr functions.
+[*Note 6*: The algorithm `lexicographical_compare_three_way` is defined
+in [[algorithms]]. — *end note*]
 All of the containers defined in this Clause and in  [[basic.string]]
 except `array` meet the additional requirements of an allocator-aware
+container, as described in [[container.alloc.req]].
 Given an allocator type `A` and given a container type `X` having a
 `value_type` identical to `T` and an `allocator_type` identical to
 `allocator_traits<A>::rebind_alloc<T>` and given an lvalue `m` of type
 `A`, a pointer `p` of type `T*`, an expression `v` of type (possibly
 `const`) `T`, and an rvalue `rv` of type `T`, the following terms are
 defined. If `X` is not allocator-aware, the terms below are defined as
 if `A` were `allocator<T>` — no allocator object needs to be created and
 user specializations of `allocator<T>` are not instantiated:
+- `T` is **Cpp17DefaultInsertable* into `X`* means that the following
   expression is well-formed:
   ``` cpp
   allocator_traits<A>::construct(m, p)
   ```
 - An element of `X` is *default-inserted* if it is initialized by
   allocator_traits<A>::construct(m, p)
   ```
   where `p` is the address of the uninitialized storage for the element
   allocated within `X`.
+- `T` is **Cpp17MoveInsertable* into `X`* means that the following
+ expression is well-formed:
   ``` cpp
   allocator_traits<A>::construct(m, p, rv)
   ```
   and its evaluation causes the following postcondition to hold: The
   value of `*p` is equivalent to the value of `rv` before the
   evaluation.
   \[*Note 7*: `rv` remains a valid object. Its state is
   unspecified — *end note*]
+- `T` is **Cpp17CopyInsertable* into `X`* means that, in addition to `T`
+  being *Cpp17MoveInsertable* into `X`, the following expression is
   well-formed:
   ``` cpp
   allocator_traits<A>::construct(m, p, v)
   ```
   and its evaluation causes the following postcondition to hold: The
   value of `v` is unchanged and is equivalent to `*p`.
+- `T` is **Cpp17EmplaceConstructible* into `X` from `args`*, for zero or
+ more arguments `args`, means that the following expression is
+  well-formed:
   ``` cpp
   allocator_traits<A>::construct(m, p, args)
   ```
+- `T` is **Cpp17Erasable* from `X`* means that the following expression
+ is well-formed:
   ``` cpp
   allocator_traits<A>::destroy(m, p)
   ```
 [*Note 8*: A container calls
 `allocator_traits<A>::construct(m, p, args)` to construct an element at
 `p` using `args`, with `m == get_allocator()`. The default `construct`
 in `allocator` will call `::new((void*)p) T(args)`, but specialized
 allocators may choose a different definition. — *end note*]
+In [[container.alloc.req]], `X` denotes an allocator-aware container
+class with a `value_type` of `T` using allocator of type `A`, `u`
+denotes a variable, `a` and `b` denote non-const lvalues of type `X`,
+`t` denotes an lvalue or a const rvalue of type `X`, `rv` denotes a
+non-const rvalue of type `X`, and `m` is a value of type `A`.
 The behavior of certain container member functions and deduction guides
 depends on whether types qualify as input iterators or allocators. The
 extent to which an implementation determines that a type cannot be an
 input iterator is unspecified, except that as a minimum integral types
 shall not qualify as input iterators. Likewise, the extent to which an
 implementation determines that a type cannot be an allocator is
 unspecified, except that as a minimum a type `A` shall not qualify as an
+allocator unless it meets both of the following conditions:
+- The *qualified-id* `A::value_type` is valid and denotes a type
+  [[temp.deduct]].
 - The expression `declval<A&>().allocate(size_t{})` is well-formed when
   treated as an unevaluated operand.
 ### Container data races <a id="container.requirements.dataraces">[[container.requirements.dataraces]]</a>
+For purposes of avoiding data races [[res.on.data.races]],
 implementations shall consider the following functions to be `const`:
 `begin`, `end`, `rbegin`, `rend`, `front`, `back`, `data`, `find`,
 `lower_bound`, `upper_bound`, `equal_range`, `at` and, except in
 associative or unordered associative containers, `operator[]`.
 of elements. The library also provides container adaptors that make it
 easy to construct abstract data types, such as `stack`s or `queue`s, out
 of the basic sequence container kinds (or out of other kinds of sequence
 containers that the user might define).
+[*Note 1*: The sequence containers offer the programmer different
+complexity trade-offs and should be used accordingly. `vector` is the
+type of sequence container that should be used by default. `array`
+should be used when the container has a fixed size known during
+translation. `list` or `forward_list` should be used when there are
+frequent insertions and deletions from the middle of the sequence.
+`deque` is the data structure of choice when most insertions and
+deletions take place at the beginning or at the end of the sequence.
+When choosing a container, remember `vector` is best; leave a comment to
+explain if you choose from the rest! — *end note*]
+In Tables  [[tab:container.seq.req]] and [[tab:container.seq.opt]], `X`
+denotes a sequence container class, `a` denotes a value of type `X`
+containing elements of type `T`, `u` denotes the name of a variable
+being declared, `A` denotes `X::allocator_type` if the *qualified-id*
+`X::allocator_type` is valid and denotes a type [[temp.deduct]] and
+`allocator<T>` if it doesn’t, `i` and `j` denote iterators that meet the
+*Cpp17InputIterator* requirements and refer to elements implicitly
+convertible to `value_type`, `[i, j)` denotes a valid range, `il`
+designates an object of type `initializer_list<value_type>`, `n` denotes
+a value of type `X::size_type`, `p` denotes a valid constant iterator to
+`a`, `q` denotes a valid dereferenceable constant iterator to `a`,
+`[q1, q2)` denotes a valid range of constant iterators in `a`, `t`
+denotes an lvalue or a const rvalue of `X::value_type`, and `rv` denotes
+a non-const rvalue of `X::value_type`. `Args` denotes a template
+parameter pack; `args` denotes a function parameter pack with the
+pattern `Args&&`.
 The complexities of the expressions are sequence dependent.
+[*Note 2*: `args` may directly or indirectly refer to a value in
+`a`. — *end note*]
 The iterator returned from `a.insert(p, t)` points to the copy of `t`
 inserted into `a`.
 The iterator returned from `a.insert(p, rv)` points to the copy of `rv`
 inserted into `a`.
 The iterator returned by `a.erase(q1, q2)` points to the element pointed
 to by `q2` prior to any elements being erased. If no such element
 exists, `a.end()` is returned.
+For every sequence container defined in this Clause and in [[strings]]:
 - If the constructor
   ``` cpp
   template<class InputIterator>
     X(InputIterator first, InputIterator last,
   and a type that does not qualify as an input iterator is deduced for
   that parameter, or if it has an `Allocator` template parameter and a
   type that does not qualify as an allocator is deduced for that
   parameter.
+[[container.seq.opt]] lists operations that are provided for some types
+of sequence containers but not others. An implementation shall provide
+these operations for all container types shown in the “container”
+column, and shall implement them so as to take amortized constant time.
 The member function `at()` provides bounds-checked access to container
 elements. `at()` throws `out_of_range` if `n >= a.size()`.
 ### Node handles <a id="container.node">[[container.node]]</a>
+#### Overview <a id="container.node.overview">[[container.node.overview]]</a>
 A *node handle* is an object that accepts ownership of a single element
+from an associative container [[associative.reqmts]] or an unordered
+associative container [[unord.req]]. It may be used to transfer that
 ownership to another container with compatible nodes. Containers with
 compatible nodes have the same node handle type. Elements may be
 transferred in either direction between container types in the same row
+of [[container.node.compat]].
+**Table: Container types with compatible nodes** <a id="container.node.compat">[container.node.compat]</a>
 |                                  |                                       |
 | -------------------------------- | ------------------------------------- |
 | `map<K, T, C1, A>`               | `map<K, T, C2, A>`                    |
 | `map<K, T, C1, A>`               | `multimap<K, T, C2, A>`               |
 If a node handle is not empty, then it contains an allocator that is
 equal to the allocator of the container when the element was extracted.
 If a node handle is empty, it contains no allocator.
+Class *`node-handle`* is for exposition only.
 If a user-defined specialization of `pair` exists for
 `pair<const Key, T>` or `pair<Key, T>`, where `Key` is the container’s
 `key_type` and `T` is the container’s `mapped_type`, the behavior of
 operations involving node handles is undefined.
 ``` cpp
 template<unspecified>
+class node-handle {
 public:
+ // These type declarations are described in Tables [tab:container.assoc.req] and [tab:container.hash.req].
   using value_type     = see below;     // not present for map containers
   using key_type       = see below;     // not present for set containers
   using mapped_type    = see below;     // not present for set containers
   using allocator_type = see below;
 private:
   using container_node_type = unspecified;
   using ator_traits = allocator_traits<allocator_type>;
+ typename ator_traits::template rebind_traits<container_node_type>::pointer ptr_;
   optional<allocator_type> alloc_;
 public:
+  // [container.node.cons], constructors, copy, and assignment
+  constexpr node-handle() noexcept : ptr_(), alloc_() {}
+  node-handle(node-handle&&) noexcept;
+  node-handle& operator=(node-handle&&);
+  // [container.node.dtor], destructor
+  ~node-handle();
+  // [container.node.observers], observers
   value_type& value() const;            // not present for map containers
   key_type& key() const;                // not present for set containers
   mapped_type& mapped() const;          // not present for set containers
   allocator_type get_allocator() const;
   explicit operator bool() const noexcept;
+  [[nodiscard]] bool empty() const noexcept;
+  // [container.node.modifiers], modifiers
+  void swap(node-handle&)
     noexcept(ator_traits::propagate_on_container_swap::value ||
              ator_traits::is_always_equal::value);
+ friend void swap(node-handle& x, node-handle& y) noexcept(noexcept(x.swap(y))) {
     x.swap(y);
   }
 };
 ```
+#### Constructors, copy, and assignment <a id="container.node.cons">[[container.node.cons]]</a>
 ``` cpp
+node-handle(node-handle&& nh) noexcept;
 ```
+*Effects:* Constructs a *node-handle* object initializing `ptr_` with
 `nh.ptr_`. Move constructs `alloc_` with `nh.alloc_`. Assigns `nullptr`
 to `nh.ptr_` and assigns `nullopt` to `nh.alloc_`.
 ``` cpp
+node-handle& operator=(node-handle&& nh);
 ```
+*Preconditions:* Either `!alloc_`, or
+`ator_traits::propagate_on_container_move_assignment::value` is `true`,
+or `alloc_ == nh.alloc_`.
 *Effects:*
 - If `ptr_ != nullptr`, destroys the `value_type` subobject in the
   `container_node_type` object pointed to by `ptr_` by calling
   `ator_traits::destroy`, then deallocates `ptr_` by calling
+  `ator_traits::template rebind_traits<container_node_type>::deallocate`.
 - Assigns `nh.ptr_` to `ptr_`.
+- If `!alloc` or
+  `ator_traits::propagate_on_container_move_assignment::value` is
+  `true`, move assigns `nh.alloc_` to `alloc_`.
 - Assigns `nullptr` to `nh.ptr_` and assigns `nullopt` to `nh.alloc_`.
 *Returns:* `*this`.
 *Throws:* Nothing.
+#### Destructor <a id="container.node.dtor">[[container.node.dtor]]</a>
 ``` cpp
+~node-handle();
 ```
 *Effects:* If `ptr_ != nullptr`, destroys the `value_type` subobject in
 the `container_node_type` object pointed to by `ptr_` by calling
 `ator_traits::destroy`, then deallocates `ptr_` by calling
+`ator_traits::template rebind_traits<container_node_type>::deallocate`.
+#### Observers <a id="container.node.observers">[[container.node.observers]]</a>
 ``` cpp
 value_type& value() const;
 ```
+*Preconditions:* `empty() == false`.
 *Returns:* A reference to the `value_type` subobject in the
 `container_node_type` object pointed to by `ptr_`.
 *Throws:* Nothing.
 ``` cpp
 key_type& key() const;
 ```
+*Preconditions:* `empty() == false`.
 *Returns:* A non-const reference to the `key_type` member of the
 `value_type` subobject in the `container_node_type` object pointed to by
 `ptr_`.
 ``` cpp
 mapped_type& mapped() const;
 ```
+*Preconditions:* `empty() == false`.
 *Returns:* A reference to the `mapped_type` member of the `value_type`
 subobject in the `container_node_type` object pointed to by `ptr_`.
 *Throws:* Nothing.
 ``` cpp
 allocator_type get_allocator() const;
 ```
+*Preconditions:* `empty() == false`.
 *Returns:* `*alloc_`.
 *Throws:* Nothing.
 ```
 *Returns:* `ptr_ != nullptr`.
 ``` cpp
+[[nodiscard]] bool empty() const noexcept;
 ```
 *Returns:* `ptr_ == nullptr`.
+#### Modifiers <a id="container.node.modifiers">[[container.node.modifiers]]</a>
 ``` cpp
+void swap(node-handle& nh)
   noexcept(ator_traits::propagate_on_container_swap::value ||
            ator_traits::is_always_equal::value);
 ```
+*Preconditions:* `!alloc_`, or `!nh.alloc_`, or
+`ator_traits::propagate_on_container_swap::value` is `true`, or
 `alloc_ == nh.alloc_`.
 *Effects:* Calls `swap(ptr_, nh.ptr_)`. If `!alloc_`, or `!nh.alloc_`,
+or `ator_traits::propagate_on_container_swap::value` is `true` calls
 `swap(alloc_, nh.alloc_)`.
 ### Insert return type <a id="container.insert.return">[[container.insert.return]]</a>
 The associative containers with unique keys and the unordered containers
 with unique keys have a member function `insert` that returns a nested
 type `insert_return_type`. That return type is a specialization of the
+template specified in this subclause.
 ``` cpp
 template<class Iterator, class NodeType>
+struct insert-return-type
 {
   Iterator position;
   bool     inserted;
   NodeType node;
 };
 ```
+The name *`insert-return-type`* is exposition only.
+*`insert-return-type`* has the template parameters, data members, and
+special members specified above. It has no base classes or members other
+than those specified.
 ### Associative containers <a id="associative.reqmts">[[associative.reqmts]]</a>
 Associative containers provide fast retrieval of data based on keys. The
 library provides four basic kinds of associative containers: `set`,
 `multiset`, `map` and `multimap`.
 Each associative container is parameterized on `Key` and an ordering
+relation `Compare` that induces a strict weak ordering [[alg.sorting]]
+on elements of `Key`. In addition, `map` and `multimap` associate an
+arbitrary *mapped type* `T` with the `Key`. The object of type `Compare`
+is called the *comparison object* of a container.
 The phrase “equivalence of keys” means the equivalence relation imposed
+by the comparison object. That is, two keys `k1` and `k2` are considered
+to be equivalent if for the comparison object `comp`,
+`comp(k1, k2) == false && comp(k2, k1) == false`.
+[*Note 1*: This is not necessarily the same as the result of
+`k1 == k2`. — *end note*]
+For any two keys `k1` and `k2` in the same container, calling
+`comp(k1, k2)` shall always return the same value.
 An associative container supports *unique keys* if it may contain at
 most one element for each key. Otherwise, it supports *equivalent keys*.
 The `set` and `map` classes support unique keys; the `multiset` and
 `multimap` classes support equivalent keys. For `multiset` and
 For associative containers where the value type is the same as the key
 type, both `iterator` and `const_iterator` are constant iterators. It is
 unspecified whether or not `iterator` and `const_iterator` are the same
 type.
+[*Note 2*: `iterator` and `const_iterator` have identical semantics in
 this case, and `iterator` is convertible to `const_iterator`. Users can
 avoid violating the one-definition rule by always using `const_iterator`
 in their function parameter lists. — *end note*]
 The associative containers meet all the requirements of Allocator-aware
+containers [[container.requirements.general]], except that for `map` and
+`multimap`, the requirements placed on `value_type` in
+[[container.alloc.req]] apply instead to `key_type` and `mapped_type`.
+[*Note 3*: For example, in some cases `key_type` and `mapped_type` are
+required to be *Cpp17CopyAssignable* even though the associated
+`value_type`, `pair<const key_type, mapped_type>`, is not
+*Cpp17CopyAssignable*. — *end note*]
+In [[container.assoc.req]], `X` denotes an associative container class,
+`a` denotes a value of type `X`, `a2` denotes a value of a type with
+nodes compatible with type `X` ([[container.node.compat]]), `b` denotes
+a possibly `const` value of type `X`, `u` denotes the name of a variable
+being declared, `a_uniq` denotes a value of type `X` when `X` supports
+unique keys, `a_eq` denotes a value of type `X` when `X` supports
+multiple keys, `a_tran` denotes a possibly `const` value of type `X`
+when the *qualified-id* `X::key_compare::is_transparent` is valid and
+denotes a type [[temp.deduct]], `i` and `j` meet the
+*Cpp17InputIterator* requirements and refer to elements implicitly
+convertible to `value_type`, \[`i`, `j`) denotes a valid range, `p`
+denotes a valid constant iterator to `a`, `q` denotes a valid
+dereferenceable constant iterator to `a`, `r` denotes a valid
+dereferenceable iterator to `a`, `[q1, q2)` denotes a valid range of
+constant iterators in `a`, `il` designates an object of type
 `initializer_list<value_type>`, `t` denotes a value of type
 `X::value_type`, `k` denotes a value of type `X::key_type` and `c`
 denotes a possibly `const` value of type `X::key_compare`; `kl` is a
+value such that `a` is partitioned [[alg.sorting]] with respect to
 `c(r, kl)`, with `r` the key value of `e` and `e` in `a`; `ku` is a
 value such that `a` is partitioned with respect to `!c(ku, r)`; `ke` is
 a value such that `a` is partitioned with respect to `c(r, ke)` and
 `!c(ke, r)`, with `c(r, ke)` implying `!c(ke, r)`. `A` denotes the
 storage allocator used by `X`, if any, or `allocator<X::value_type>`
 ```
 When an associative container is constructed by passing a comparison
 object the container shall not store a pointer or reference to the
 passed object, even if that object is passed by reference. When an
+associative container is copied, through either a copy constructor or an
 assignment operator, the target container shall then use the comparison
 object from the container being copied, as if that comparison object had
 been passed to the target container in its constructor.
+The member function templates `find`, `count`, `contains`,
+`lower_bound`, `upper_bound`, and `equal_range` shall not participate in
+overload resolution unless the *qualified-id* `Compare::is_transparent`
+is valid and denotes a type [[temp.deduct]].
 A deduction guide for an associative container shall not participate in
 overload resolution if any of the following are true:
 - It has an `InputIterator` template parameter and a type that does not
 linear, but the average case is much faster. The library provides four
 unordered associative containers: `unordered_set`, `unordered_map`,
 `unordered_multiset`, and `unordered_multimap`.
 Unordered associative containers conform to the requirements for
+Containers [[container.requirements]], except that the expressions
 `a == b` and `a != b` have different semantics than for the other
 container types.
 Each unordered associative container is parameterized by `Key`, by a
+function object type `Hash` that meets the *Cpp17Hash* requirements
+[[hash.requirements]] and acts as a hash function for argument values of
+type `Key`, and by a binary predicate `Pred` that induces an equivalence
+relation on values of type `Key`. Additionally, `unordered_map` and
+`unordered_multimap` associate an arbitrary *mapped type* `T` with the
+`Key`.
 The container’s object of type `Hash` — denoted by `hash` — is called
 the *hash function* of the container. The container’s object of type
 `Pred` — denoted by `pred` — is called the *key equality predicate* of
 the container.
+Two values `k1` and `k2` are considered equivalent if the container’s
+key equality predicate `pred(k1, k2)` is valid and returns `true` when
+passed those values. If `k1` and `k2` are equivalent, the container’s
+hash function shall return the same value for both.
 [*Note 1*: Thus, when an unordered associative container is
 instantiated with a non-default `Pred` parameter it usually needs a
 non-default `Hash` parameter as well. — *end note*]
 appear in, but does not invalidate pointers or references to elements.
 For `unordered_multiset` and `unordered_multimap`, rehashing preserves
 the relative ordering of equivalent elements.
 The unordered associative containers meet all the requirements of
+Allocator-aware containers [[container.requirements.general]], except
 that for `unordered_map` and `unordered_multimap`, the requirements
+placed on `value_type` in [[container.alloc.req]] apply instead to
+`key_type` and `mapped_type`.
 [*Note 3*: For example, `key_type` and `mapped_type` are sometimes
+required to be *Cpp17CopyAssignable* even though the associated
+`value_type`, `pair<const key_type, mapped_type>`, is not
+*Cpp17CopyAssignable*. — *end note*]
+In [[container.hash.req]]:
+- `X` denotes an unordered associative container class,
+- `a` denotes a value of type `X`,
+- `a2` denotes a value of a type with nodes compatible with type `X` (
+  [[container.node.compat]]),
+- `b` denotes a possibly const value of type `X`,
+- `a_uniq` denotes a value of type `X` when `X` supports unique keys,
+- `a_eq` denotes a value of type `X` when `X` supports equivalent keys,
+- `a_tran` denotes a possibly const value of type `X` when the
+  *qualified-id*s `X::key_equal::is_transparent` and
+ `X::hasher::is_transparent` are both valid and denote types
+  [[temp.deduct]],
+- `i` and `j` denote input iterators that refer to `value_type`,
+- `[i, j)` denotes a valid range,
+- `p` and `q2` denote valid constant iterators to `a`,
+- `q` and `q1` denote valid dereferenceable constant iterators to `a`,
+- `r` denotes a valid dereferenceable iterator to `a`,
+- `[q1, q2)` denotes a valid range in `a`,
+- `il` denotes a value of type `initializer_list<value_type>`,
+- `t` denotes a value of type `X::value_type`,
+- `k` denotes a value of type `key_type`,
+- `hf` denotes a possibly const value of type `hasher`,
+- `eq` denotes a possibly const value of type `key_equal`,
+- `ke` is a value such that
+  - `eq(r1, ke) == eq(ke, r1)`
+  - `hf(r1) == hf(ke)` if `eq(r1, ke)` is `true`, and
+  - `(eq(r1, ke) && eq(r1, r2)) == eq(r2, ke)`
+  where `r1` and `r2` are keys of elements in `a_tran`,
+- `n` denotes a value of type `size_type`,
+- `z` denotes a value of type `float`, and
+- `nh` denotes a non-const rvalue of type `X::node_type`.
 Two unordered containers `a` and `b` compare equal if
 `a.size() == b.size()` and, for every equivalent-key group \[`Ea1`,
 `Ea2`) obtained from `a.equal_range(Ea1)`, there exists an
 equivalent-key group \[`Eb1`, `Eb2`) obtained from `b.equal_range(Ea1)`,
 such that `is_permutation(Ea1, Ea2, Eb1, Eb2)` returns `true`. For
 `unordered_set` and `unordered_map`, the complexity of `operator==`
 (i.e., the number of calls to the `==` operator of the `value_type`, to
 the predicate returned by `key_eq()`, and to the hasher returned by
 `hash_function()`) is proportional to N in the average case and to N² in
+the worst case, where N is `a.size()`. For `unordered_multiset` and
 `unordered_multimap`, the complexity of `operator==` is proportional to
 $\sum E_i^2$ in the average case and to N² in the worst case, where N is
 `a.size()`, and Eᵢ is the size of the iᵗʰ equivalent-key group in `a`.
 However, if the respective elements of each corresponding pair of
 equivalent-key groups Eaᵢ and Ebᵢ are arranged in the same order (as is
 commonly the case, e.g., if `a` and `b` are unmodified copies of the
 same container), then the average-case complexity for
 `unordered_multiset` and `unordered_multimap` becomes proportional to N
 (but worst-case complexity remains 𝑂(N^2), e.g., for a pathologically
 bad hash function). The behavior of a program that uses `operator==` or
+`operator!=` on unordered containers is undefined unless the `Pred`
+function object has the same behavior for both containers and the
+equality comparison function for `Key` is a refinement[^1] of the
+partition into equivalent-key groups produced by `Pred`.
 The iterator types `iterator` and `const_iterator` of an unordered
 associative container are of at least the forward iterator category. For
 unordered associative containers where the key type and value type are
 the same, both `iterator` and `const_iterator` are constant iterators.
 accessing the element through such pointers and references while the
 element is owned by a `node_type` is undefined behavior. References and
 pointers to an element obtained while it is owned by a `node_type` are
 invalidated if the element is successfully inserted.
+The member function templates `find`, `count`, `equal_range`, and
+`contains` shall not participate in overload resolution unless the
+*qualified-id*s `Pred::is_transparent` and `Hash::is_transparent` are
+both valid and denote types [[temp.deduct]].
 A deduction guide for an unordered associative container shall not
 participate in overload resolution if any of the following are true:
 - It has an `InputIterator` template parameter and a type that does not
   qualify as an input iterator is deduced for that parameter.
 The headers `<array>`, `<deque>`, `<forward_list>`, `<list>`, and
 `<vector>` define class templates that meet the requirements for
 sequence containers.
+The following exposition-only alias template may appear in deduction
+guides for sequence containers:
+``` cpp
+template<class InputIterator>
+  using iter-value-type = typename iterator_traits<InputIterator>::value_type;  // exposition only
+```
 ### Header `<array>` synopsis <a id="array.syn">[[array.syn]]</a>
 ``` cpp
+#include <compare>              // see [compare.syn]
+#include <initializer_list>     // see [initializer.list.syn]
 namespace std {
   // [array], class template array
   template<class T, size_t N> struct array;
   template<class T, size_t N>
+ constexpr bool operator==(const array<T, N>& x, const array<T, N>& y);
   template<class T, size_t N>
+ constexpr synth-three-way-result<T>
+      operator<=>(const array<T, N>& x, const array<T, N>& y);
+  // [array.special], specialized algorithms
   template<class T, size_t N>
+ constexpr void swap(array<T, N>& x, array<T, N>& y) noexcept(noexcept(x.swap(y)));
+  // [array.creation], array creation functions
   template<class T, size_t N>
+ constexpr array<remove_cv_t<T>, N> to_array(T (&a)[N]);
   template<class T, size_t N>
+ constexpr array<remove_cv_t<T>, N> to_array(T (&&a)[N]);
+ // [array.tuple], tuple interface
+  template<class T> struct tuple_size;
+  template<size_t I, class T> struct tuple_element;
   template<class T, size_t N>
     struct tuple_size<array<T, N>>;
   template<size_t I, class T, size_t N>
     struct tuple_element<I, array<T, N>>;
   template<size_t I, class T, size_t N>
 ```
 ### Header `<deque>` synopsis <a id="deque.syn">[[deque.syn]]</a>
 ``` cpp
+#include <compare>              // see [compare.syn]
+#include <initializer_list>     // see [initializer.list.syn]
 namespace std {
   // [deque], class template deque
   template<class T, class Allocator = allocator<T>> class deque;
   template<class T, class Allocator>
     bool operator==(const deque<T, Allocator>& x, const deque<T, Allocator>& y);
   template<class T, class Allocator>
+ synth-three-way-result<T> operator<=>(const deque<T, Allocator>& x,
+    \itcorr                                      const deque<T, Allocator>& y);
   template<class T, class Allocator>
     void swap(deque<T, Allocator>& x, deque<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
+  template<class T, class Allocator, class U>
+    typename deque<T, Allocator>::size_type
+      erase(deque<T, Allocator>& c, const U& value);
+  template<class T, class Allocator, class Predicate>
+    typename deque<T, Allocator>::size_type
+      erase_if(deque<T, Allocator>& c, Predicate pred);
   namespace pmr {
     template<class T>
       using deque = std::deque<T, polymorphic_allocator<T>>;
   }
 }
 ```
+### Header `<forward_list>` synopsis <a id="forward.list.syn">[[forward.list.syn]]</a>
 ``` cpp
+#include <compare>              // see [compare.syn]
+#include <initializer_list>     // see [initializer.list.syn]
 namespace std {
   // [forwardlist], class template forward_list
   template<class T, class Allocator = allocator<T>> class forward_list;
   template<class T, class Allocator>
     bool operator==(const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y);
   template<class T, class Allocator>
+ synth-three-way-result<T> operator<=>(const forward_list<T, Allocator>& x,
+    \itcorr                                      const forward_list<T, Allocator>& y);
   template<class T, class Allocator>
     void swap(forward_list<T, Allocator>& x, forward_list<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
+  template<class T, class Allocator, class U>
+    typename forward_list<T, Allocator>::size_type
+      erase(forward_list<T, Allocator>& c, const U& value);
+  template<class T, class Allocator, class Predicate>
+    typename forward_list<T, Allocator>::size_type
+      erase_if(forward_list<T, Allocator>& c, Predicate pred);
   namespace pmr {
     template<class T>
       using forward_list = std::forward_list<T, polymorphic_allocator<T>>;
   }
 }
 ```
 ### Header `<list>` synopsis <a id="list.syn">[[list.syn]]</a>
 ``` cpp
+#include <compare>              // see [compare.syn]
+#include <initializer_list>     // see [initializer.list.syn]
 namespace std {
   // [list], class template list
   template<class T, class Allocator = allocator<T>> class list;
   template<class T, class Allocator>
     bool operator==(const list<T, Allocator>& x, const list<T, Allocator>& y);
   template<class T, class Allocator>
+ synth-three-way-result<T> operator<=>(const list<T, Allocator>& x,
+    \itcorr                                      const list<T, Allocator>& y);
   template<class T, class Allocator>
     void swap(list<T, Allocator>& x, list<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
+  template<class T, class Allocator, class U>
+    typename list<T, Allocator>::size_type
+      erase(list<T, Allocator>& c, const U& value);
+  template<class T, class Allocator, class Predicate>
+    typename list<T, Allocator>::size_type
+      erase_if(list<T, Allocator>& c, Predicate pred);
   namespace pmr {
     template<class T>
       using list = std::list<T, polymorphic_allocator<T>>;
   }
 }
 ```
 ### Header `<vector>` synopsis <a id="vector.syn">[[vector.syn]]</a>
 ``` cpp
+#include <compare>              // see [compare.syn]
+#include <initializer_list>     // see [initializer.list.syn]
 namespace std {
   // [vector], class template vector
   template<class T, class Allocator = allocator<T>> class vector;
   template<class T, class Allocator>
+ constexpr bool operator==(const vector<T, Allocator>& x, const vector<T, Allocator>& y);
   template<class T, class Allocator>
+ constexpr synth-three-way-result<T> operator<=>(const vector<T, Allocator>& x,
+              \itcorr                                      const vector<T, Allocator>& y);
   template<class T, class Allocator>
+ constexpr void swap(vector<T, Allocator>& x, vector<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
+  template<class T, class Allocator, class U>
+    constexpr typename vector<T, Allocator>::size_type
+      erase(vector<T, Allocator>& c, const U& value);
+  template<class T, class Allocator, class Predicate>
+    constexpr typename vector<T, Allocator>::size_type
+      erase_if(vector<T, Allocator>& c, Predicate pred);
   // [vector.bool], class vector<bool>
   template<class Allocator> class vector<bool, Allocator>;
   // hash support
   template<class T> struct hash;
 }
 ```
 ### Class template `array` <a id="array">[[array]]</a>
+#### Overview <a id="array.overview">[[array.overview]]</a>
 The header `<array>` defines a class template for storing fixed-size
+sequences of objects. An `array` is a contiguous container
+[[container.requirements.general]]. An instance of `array<T, N>` stores
 `N` elements of type `T`, so that `size() == N` is an invariant.
+An `array` is an aggregate [[dcl.init.aggr]] that can be
 list-initialized with up to `N` elements whose types are convertible to
 `T`.
+An `array` meets all of the requirements of a container and of a
+reversible container [[container.requirements]], except that a default
+constructed `array` object is not empty and that `swap` does not have
+constant complexity. An `array` meets some of the requirements of a
+sequence container [[sequence.reqmts]]. Descriptions are provided here
+only for operations on `array` that are not described in one of these
+tables and for operations where there is additional semantic
+information.
+`array<T, N>` is a structural type [[temp.param]] if `T` is a structural
+type. Two values `a1` and `a2` of type `array<T, N>` are
+template-argument-equivalent [[temp.type]] if and only if each pair of
+corresponding elements in `a1` and `a2` are
+template-argument-equivalent.
+The types `iterator` and `const_iterator` meet the constexpr iterator
+requirements [[iterator.requirements.general]].
 ``` cpp
 namespace std {
   template<class T, size_t N>
   struct array {
+    // types
     using value_type             = T;
     using pointer                = T*;
     using const_pointer          = const T*;
     using reference              = T&;
     using const_reference        = const T&;
     using reverse_iterator       = std::reverse_iterator<iterator>;
     using const_reverse_iterator = std::reverse_iterator<const_iterator>;
     // no explicit construct/copy/destroy for aggregate type
+ constexpr void fill(const T& u);
+ constexpr void swap(array&) noexcept(is_nothrow_swappable_v<T>);
+    // iterators
     constexpr iterator               begin() noexcept;
     constexpr const_iterator         begin() const noexcept;
     constexpr iterator               end() noexcept;
     constexpr const_iterator         end() const noexcept;
     constexpr const_iterator         cbegin() const noexcept;
     constexpr const_iterator         cend() const noexcept;
     constexpr const_reverse_iterator crbegin() const noexcept;
     constexpr const_reverse_iterator crend() const noexcept;
+    // capacity
+ [[nodiscard]] constexpr bool empty() const noexcept;
     constexpr size_type size() const noexcept;
     constexpr size_type max_size() const noexcept;
+    // element access
     constexpr reference       operator[](size_type n);
     constexpr const_reference operator[](size_type n) const;
     constexpr reference       at(size_type n);
     constexpr const_reference at(size_type n) const;
     constexpr reference       front();
   template<class T, class... U>
     array(T, U...) -> array<T, 1 + sizeof...(U)>;
 }
 ```
+#### Constructors, copy, and assignment <a id="array.cons">[[array.cons]]</a>
+The conditions for an aggregate [[dcl.init.aggr]] shall be met. Class
 `array` relies on the implicitly-declared special member functions (
+[[class.default.ctor]], [[class.dtor]], and [[class.copy.ctor]]) to
+conform to the container requirements table in
+[[container.requirements]]. In addition to the requirements specified in
+the container requirements table, the implicit move constructor and move
+assignment operator for `array` require that `T` be
+*Cpp17MoveConstructible* or *Cpp17MoveAssignable*, respectively.
 ``` cpp
 template<class T, class... U>
   array(T, U...) -> array<T, 1 + sizeof...(U)>;
 ```
+*Mandates:* `(is_same_v<T, U> && ...)` is `true`.
+#### Member functions <a id="array.members">[[array.members]]</a>
 ``` cpp
+constexpr size_type size() const noexcept;
 ```
 *Returns:* `N`.
 ``` cpp
 constexpr T* data() noexcept;
 constexpr const T* data() const noexcept;
 ```
+*Returns:* A pointer such that \[`data()`, `data() + size()`) is a valid
+range. For a non-empty array, `data()` `==` `addressof(front())`.
 ``` cpp
+constexpr void fill(const T& u);
 ```
 *Effects:* As if by `fill_n(begin(), N, u)`.
 ``` cpp
+constexpr void swap(array& y) noexcept(is_nothrow_swappable_v<T>);
 ```
 *Effects:* Equivalent to `swap_ranges(begin(), end(), y.begin())`.
 [*Note 1*: Unlike the `swap` function for other containers,
 `array::swap` takes linear time, may exit via an exception, and does not
 cause iterators to become associated with the other
 container. — *end note*]
+#### Specialized algorithms <a id="array.special">[[array.special]]</a>
+``` cpp
+template<class T, size_t N>
+  constexpr void swap(array<T, N>& x, array<T, N>& y) noexcept(noexcept(x.swap(y)));
+```
+*Constraints:* `N == 0` or `is_swappable_v<T>` is `true`.
+*Effects:* As if by `x.swap(y)`.
+*Complexity:* Linear in `N`.
+#### Zero-sized arrays <a id="array.zero">[[array.zero]]</a>
 `array` shall provide support for the special case `N == 0`.
 In the case that `N == 0`, `begin() == end() ==` unique value. The
 return value of `data()` is unspecified.
 undefined.
 Member function `swap()` shall have a non-throwing exception
 specification.
+#### Array creation functions <a id="array.creation">[[array.creation]]</a>
+``` cpp
+template<class T, size_t N>
+  constexpr array<remove_cv_t<T>, N> to_array(T (&a)[N]);
+```
+*Mandates:* `is_array_v<T>` is `false` and `is_constructible_v<T, T&>`
+is `true`.
+*Preconditions:* `T` meets the *Cpp17CopyConstructible* requirements.
+*Returns:* `{{ a[0], `…`, a[N - 1] }}`.
+``` cpp
+template<class T, size_t N>
+  constexpr array<remove_cv_t<T>, N> to_array(T (&&a)[N]);
+```
+*Mandates:* `is_array_v<T>` is `false` and `is_move_constructible_v<T>`
+is `true`.
+*Preconditions:* `T` meets the *Cpp17MoveConstructible* requirements.
+*Returns:* `{{ std::move(a[0]), `…`, std::move(a[N - 1]) }}`.
+#### Tuple interface <a id="array.tuple">[[array.tuple]]</a>
 ``` cpp
 template<class T, size_t N>
   struct tuple_size<array<T, N>> : integral_constant<size_t, N> { };
 ```
 ``` cpp
+template<size_t I, class T, size_t N>
+  struct tuple_element<I, array<T, N>> {
+    using type = T;
+  };
 ```
+*Mandates:* `I < N` is `true`.
 ``` cpp
 template<size_t I, class T, size_t N>
   constexpr T& get(array<T, N>& a) noexcept;
 template<size_t I, class T, size_t N>
   constexpr const T& get(const array<T, N>& a) noexcept;
 template<size_t I, class T, size_t N>
   constexpr const T&& get(const array<T, N>&& a) noexcept;
 ```
+*Mandates:* `I < N` is `true`.
+*Returns:* A reference to the `I`ᵗʰ element of `a`, where indexing is
 zero-based.
 ### Class template `deque` <a id="deque">[[deque]]</a>
+#### Overview <a id="deque.overview">[[deque.overview]]</a>
 A `deque` is a sequence container that supports random access iterators
+[[random.access.iterators]]. In addition, it supports constant time
 insert and erase operations at the beginning or the end; insert and
 erase in the middle take linear time. That is, a deque is especially
 optimized for pushing and popping elements at the beginning and end.
 Storage management is handled automatically.
+A `deque` meets all of the requirements of a container, of a reversible
+container (given in tables in  [[container.requirements]]), of a
+sequence container, including the optional sequence container
+requirements [[sequence.reqmts]], and of an allocator-aware container (
+[[container.alloc.req]]). Descriptions are provided here only for
+operations on `deque` that are not described in one of these tables or
+for operations where there is additional semantic information.
 ``` cpp
 namespace std {
   template<class T, class Allocator = allocator<T>>
   class deque {
   public:
+    // types
     using value_type             = T;
     using allocator_type         = Allocator;
     using pointer                = typename allocator_traits<Allocator>::pointer;
     using const_pointer          = typename allocator_traits<Allocator>::const_pointer;
     using reference              = value_type&;
       void assign(InputIterator first, InputIterator last);
     void assign(size_type n, const T& t);
     void assign(initializer_list<T>);
     allocator_type get_allocator() const noexcept;
+    // iterators
     iterator               begin() noexcept;
     const_iterator         begin() const noexcept;
     iterator               end() noexcept;
     const_iterator         end() const noexcept;
     reverse_iterator       rbegin() noexcept;
     const_iterator         cend() const noexcept;
     const_reverse_iterator crbegin() const noexcept;
     const_reverse_iterator crend() const noexcept;
     // [deque.capacity], capacity
+ [[nodiscard]] bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
     void      resize(size_type sz);
     void      resize(size_type sz, const T& c);
     void      shrink_to_fit();
+    // element access
     reference       operator[](size_type n);
     const_reference operator[](size_type n) const;
     reference       at(size_type n);
     const_reference at(size_type n) const;
     reference       front();
     void     swap(deque&)
       noexcept(allocator_traits<Allocator>::is_always_equal::value);
     void     clear() noexcept;
   };
+  template<class InputIterator, class Allocator = allocator<iter-value-type<InputIterator>>>
     deque(InputIterator, InputIterator, Allocator = Allocator())
+      -> deque<iter-value-type<InputIterator>, Allocator>;
+ // swap
   template<class T, class Allocator>
     void swap(deque<T, Allocator>& x, deque<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
+#### Constructors, copy, and assignment <a id="deque.cons">[[deque.cons]]</a>
 ``` cpp
 explicit deque(const Allocator&);
 ```
 ```
 *Effects:* Constructs a `deque` with `n` default-inserted elements using
 the specified allocator.
+*Preconditions:* `T` is *Cpp17DefaultInsertable* into `*this`.
 *Complexity:* Linear in `n`.
 ``` cpp
 deque(size_type n, const T& value, const Allocator& = Allocator());
 ```
 *Effects:* Constructs a `deque` with `n` copies of `value`, using the
 specified allocator.
+*Preconditions:* `T` is *Cpp17CopyInsertable* into `*this`.
 *Complexity:* Linear in `n`.
 ``` cpp
 template<class InputIterator>
 *Effects:* Constructs a `deque` equal to the range \[`first`, `last`),
 using the specified allocator.
 *Complexity:* Linear in `distance(first, last)`.
+#### Capacity <a id="deque.capacity">[[deque.capacity]]</a>
 ``` cpp
 void resize(size_type sz);
 ```
+*Preconditions:* `T` is *Cpp17MoveInsertable* and
+*Cpp17DefaultInsertable* into `*this`.
 *Effects:* If `sz < size()`, erases the last `size() - sz` elements from
 the sequence. Otherwise, appends `sz - size()` default-inserted elements
 to the sequence.
 ``` cpp
 void resize(size_type sz, const T& c);
 ```
+*Preconditions:* `T` is *Cpp17CopyInsertable* into `*this`.
 *Effects:* If `sz < size()`, erases the last `size() - sz` elements from
 the sequence. Otherwise, appends `sz - size()` copies of `c` to the
 sequence.
 ``` cpp
 void shrink_to_fit();
 ```
+*Preconditions:* `T` is *Cpp17MoveInsertable* into `*this`.
 *Effects:* `shrink_to_fit` is a non-binding request to reduce memory use
 but does not change the size of the sequence.
 [*Note 1*: The request is non-binding to allow latitude for
 implementation-specific optimizations. — *end note*]
+If the size is equal to the old capacity, or if an exception is thrown
+other than by the move constructor of a non-*Cpp17CopyInsertable* `T`,
+then there are no effects.
+*Complexity:* If the size is not equal to the old capacity, linear in
+the size of the sequence; otherwise constant.
+*Remarks:* If the size is not equal to the old capacity, then
+invalidates all the references, pointers, and iterators referring to the
+elements in the sequence, as well as the past-the-end iterator.
+#### Modifiers <a id="deque.modifiers">[[deque.modifiers]]</a>
 ``` cpp
 iterator insert(const_iterator position, const T& x);
 iterator insert(const_iterator position, T&& x);
 iterator insert(const_iterator position, size_type n, const T& x);
 *Remarks:* If an exception is thrown other than by the copy constructor,
 move constructor, assignment operator, or move assignment operator of
 `T` there are no effects. If an exception is thrown while inserting a
 single element at either end, there are no effects. Otherwise, if an
+exception is thrown by the move constructor of a
+non-*Cpp17CopyInsertable* `T`, the effects are unspecified.
 *Complexity:* The complexity is linear in the number of elements
 inserted plus the lesser of the distances to the beginning and end of
+the deque. Inserting a single element at either the beginning or end of
 a deque always takes constant time and causes a single call to a
 constructor of `T`.
 ``` cpp
 iterator erase(const_iterator position);
 as the number of elements erased, but the number of calls to the
 assignment operator of `T` is no more than the lesser of the number of
 elements before the erased elements and the number of elements after the
 erased elements.
+*Throws:* Nothing unless an exception is thrown by the assignment
+operator of `T`.
+#### Erasure <a id="deque.erasure">[[deque.erasure]]</a>
 ``` cpp
+template<class T, class Allocator, class U>
+ typename deque<T, Allocator>::size_type
+ erase(deque<T, Allocator>& c, const U& value);
 ```
+*Effects:* Equivalent to:
+``` cpp
+auto it = remove(c.begin(), c.end(), value);
+auto r = distance(it, c.end());
+c.erase(it, c.end());
+return r;
+```
+``` cpp
+template<class T, class Allocator, class Predicate>
+  typename deque<T, Allocator>::size_type
+    erase_if(deque<T, Allocator>& c, Predicate pred);
+```
+*Effects:* Equivalent to:
+``` cpp
+auto it = remove_if(c.begin(), c.end(), pred);
+auto r = distance(it, c.end());
+c.erase(it, c.end());
+return r;
+```
 ### Class template `forward_list` <a id="forwardlist">[[forwardlist]]</a>
+#### Overview <a id="forwardlist.overview">[[forwardlist.overview]]</a>
 A `forward_list` is a container that supports forward iterators and
 allows constant time insert and erase operations anywhere within the
 sequence, with storage management handled automatically. Fast random
 access to list elements is not supported.
 [*Note 1*: It is intended that `forward_list` have zero space or time
 overhead relative to a hand-written C-style singly linked list. Features
 that would conflict with that goal have been omitted. — *end note*]
+A `forward_list` meets all of the requirements of a container (
+[[container.req]]), except that the `size()` member function is not
+provided and `operator==` has linear complexity. A `forward_list` also
+meets all of the requirements for an allocator-aware container (
+[[container.alloc.req]]). In addition, a `forward_list` provides the
+`assign` member functions ([[container.seq.req]]) and several of the
+optional container requirements ([[container.seq.opt]]). Descriptions
+are provided here only for operations on `forward_list` that are not
+described in that table or for operations where there is additional
+semantic information.
 [*Note 2*: Modifying any list requires access to the element preceding
 the first element of interest, but in a `forward_list` there is no
 constant-time way to access a preceding element. For this reason, ranges
 that are modified, such as those supplied to `erase` and `splice`, must
 ``` cpp
 namespace std {
   template<class T, class Allocator = allocator<T>>
   class forward_list {
   public:
+    // types
     using value_type      = T;
     using allocator_type  = Allocator;
     using pointer         = typename allocator_traits<Allocator>::pointer;
     using const_pointer   = typename allocator_traits<Allocator>::const_pointer;
     using reference       = value_type&;
     // [forwardlist.cons], construct/copy/destroy
     forward_list() : forward_list(Allocator()) { }
     explicit forward_list(const Allocator&);
     explicit forward_list(size_type n, const Allocator& = Allocator());
+    forward_list(size_type n, const T& value, const Allocator& = Allocator());
     template<class InputIterator>
+      forward_list(InputIterator first, InputIterator last, const Allocator& = Allocator());
     forward_list(const forward_list& x);
     forward_list(forward_list&& x);
     forward_list(const forward_list& x, const Allocator&);
     forward_list(forward_list&& x, const Allocator&);
     forward_list(initializer_list<T>, const Allocator& = Allocator());
     const_iterator cbegin() const noexcept;
     const_iterator cbefore_begin() const noexcept;
     const_iterator cend() const noexcept;
+    // capacity
+ [[nodiscard]] bool empty() const noexcept;
     size_type max_size() const noexcept;
     // [forwardlist.access], element access
     reference front();
     const_reference front() const;
     void clear() noexcept;
     // [forwardlist.ops], forward_list operations
     void splice_after(const_iterator position, forward_list& x);
     void splice_after(const_iterator position, forward_list&& x);
+    void splice_after(const_iterator position, forward_list& x, const_iterator i);
+    void splice_after(const_iterator position, forward_list&& x, const_iterator i);
     void splice_after(const_iterator position, forward_list& x,
                       const_iterator first, const_iterator last);
     void splice_after(const_iterator position, forward_list&& x,
                       const_iterator first, const_iterator last);
+ size_type remove(const T& value);
+    template<class Predicate> size_type remove_if(Predicate pred);
+ size_type unique();
+    template<class BinaryPredicate> size_type unique(BinaryPredicate binary_pred);
     void merge(forward_list& x);
     void merge(forward_list&& x);
     template<class Compare> void merge(forward_list& x, Compare comp);
     template<class Compare> void merge(forward_list&& x, Compare comp);
     template<class Compare> void sort(Compare comp);
     void reverse() noexcept;
   };
+  template<class InputIterator, class Allocator = allocator<iter-value-type<InputIterator>>>
     forward_list(InputIterator, InputIterator, Allocator = Allocator())
+      -> forward_list<iter-value-type<InputIterator>, Allocator>;
+ // swap
   template<class T, class Allocator>
     void swap(forward_list<T, Allocator>& x, forward_list<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
 An incomplete type `T` may be used when instantiating `forward_list` if
+the allocator meets the allocator completeness requirements
+[[allocator.requirements.completeness]]. `T` shall be complete before
 any member of the resulting specialization of `forward_list` is
 referenced.
+#### Constructors, copy, and assignment <a id="forwardlist.cons">[[forwardlist.cons]]</a>
 ``` cpp
 explicit forward_list(const Allocator&);
 ```
 ``` cpp
 explicit forward_list(size_type n, const Allocator& = Allocator());
 ```
+*Preconditions:* `T` is *Cpp17DefaultInsertable* into `*this`.
 *Effects:* Constructs a `forward_list` object with `n` default-inserted
 elements using the specified allocator.
 *Complexity:* Linear in `n`.
 ``` cpp
 forward_list(size_type n, const T& value, const Allocator& = Allocator());
 ```
+*Preconditions:* `T` is *Cpp17CopyInsertable* into `*this`.
 *Effects:* Constructs a `forward_list` object with `n` copies of `value`
 using the specified allocator.
 *Complexity:* Linear in `n`.
 ``` cpp
 template<class InputIterator>
   forward_list(InputIterator first, InputIterator last, const Allocator& = Allocator());
 *Effects:* Constructs a `forward_list` object equal to the range
 \[`first`, `last`).
 *Complexity:* Linear in `distance(first, last)`.
+#### Iterators <a id="forwardlist.iter">[[forwardlist.iter]]</a>
 ``` cpp
 iterator before_begin() noexcept;
 const_iterator before_begin() const noexcept;
 const_iterator cbefore_begin() const noexcept;
 *Effects:* `cbefore_begin()` is equivalent to
 `const_cast<forward_list const&>(*this).before_begin()`.
 *Remarks:* `before_begin() == end()` shall equal `false`.
+#### Element access <a id="forwardlist.access">[[forwardlist.access]]</a>
 ``` cpp
 reference front();
 const_reference front() const;
 ```
 *Returns:* `*begin()`
+#### Modifiers <a id="forwardlist.modifiers">[[forwardlist.modifiers]]</a>
 None of the overloads of `insert_after` shall affect the validity of
 iterators and references, and `erase_after` shall invalidate only
 iterators and references to the erased elements. If an exception is
 thrown during `insert_after` there shall be no effect. Inserting `n`
 ``` cpp
 iterator insert_after(const_iterator position, const T& x);
 iterator insert_after(const_iterator position, T&& x);
 ```
+*Preconditions:* `position` is `before_begin()` or is a dereferenceable
 iterator in the range \[`begin()`, `end()`).
 *Effects:* Inserts a copy of `x` after `position`.
 *Returns:* An iterator pointing to the copy of `x`.
 ``` cpp
 iterator insert_after(const_iterator position, size_type n, const T& x);
 ```
+*Preconditions:* `position` is `before_begin()` or is a dereferenceable
 iterator in the range \[`begin()`, `end()`).
 *Effects:* Inserts `n` copies of `x` after `position`.
 *Returns:* An iterator pointing to the last inserted copy of `x` or
 ``` cpp
 template<class InputIterator>
   iterator insert_after(const_iterator position, InputIterator first, InputIterator last);
 ```
+*Preconditions:* `position` is `before_begin()` or is a dereferenceable
+iterator in the range \[`begin()`, `end()`). Neither `first` nor `last`
+are iterators in `*this`.
 *Effects:* Inserts copies of elements in \[`first`, `last`) after
 `position`.
 *Returns:* An iterator pointing to the last inserted element or
 ``` cpp
 template<class... Args>
   iterator emplace_after(const_iterator position, Args&&... args);
 ```
+*Preconditions:* `position` is `before_begin()` or is a dereferenceable
 iterator in the range \[`begin()`, `end()`).
 *Effects:* Inserts an object of type `value_type` constructed with
 `value_type(std::forward<Args>(args)...)` after `position`.
 ``` cpp
 iterator erase_after(const_iterator position);
 ```
+*Preconditions:* The iterator following `position` is dereferenceable.
 *Effects:* Erases the element pointed to by the iterator following
 `position`.
 *Returns:* An iterator pointing to the element following the one that
 ``` cpp
 iterator erase_after(const_iterator position, const_iterator last);
 ```
+*Preconditions:* All iterators in the range (`position`, `last`) are
 dereferenceable.
 *Effects:* Erases the elements in the range (`position`, `last`).
 *Returns:* `last`.
 ``` cpp
 void resize(size_type sz);
 ```
+*Preconditions:* `T` is *Cpp17DefaultInsertable* into `*this`.
 *Effects:* If `sz < distance(begin(), end())`, erases the last
 `distance(begin(), end()) - sz` elements from the list. Otherwise,
 inserts `sz - distance(begin(), end())` default-inserted elements at the
 end of the list.
 ``` cpp
 void resize(size_type sz, const value_type& c);
 ```
+*Preconditions:* `T` is *Cpp17CopyInsertable* into `*this`.
 *Effects:* If `sz < distance(begin(), end())`, erases the last
 `distance(begin(), end()) - sz` elements from the list. Otherwise,
 inserts `sz - distance(begin(), end())` copies of `c` at the end of the
 list.
 ``` cpp
 void clear() noexcept;
 ```
 *Effects:* Erases all elements in the range \[`begin()`, `end()`).
 *Remarks:* Does not invalidate past-the-end iterators.
+#### Operations <a id="forwardlist.ops">[[forwardlist.ops]]</a>
+In this subclause, arguments for a template parameter named `Predicate`
+or `BinaryPredicate` shall meet the corresponding requirements in
+[[algorithms.requirements]]. For `merge` and `sort`, the definitions and
+requirements in [[alg.sorting]] apply.
 ``` cpp
 void splice_after(const_iterator position, forward_list& x);
 void splice_after(const_iterator position, forward_list&& x);
 ```
+*Preconditions:* `position` is `before_begin()` or is a dereferenceable
 iterator in the range \[`begin()`, `end()`).
+`get_allocator() == x.get_allocator()` is `true`. `addressof(x) != this`
+is `true`.
 *Effects:* Inserts the contents of `x` after `position`, and `x` becomes
 empty. Pointers and references to the moved elements of `x` now refer to
 those same elements but as members of `*this`. Iterators referring to
 the moved elements will continue to refer to their elements, but they
 ``` cpp
 void splice_after(const_iterator position, forward_list& x, const_iterator i);
 void splice_after(const_iterator position, forward_list&& x, const_iterator i);
 ```
+*Preconditions:* `position` is `before_begin()` or is a dereferenceable
 iterator in the range \[`begin()`, `end()`). The iterator following `i`
 is a dereferenceable iterator in `x`.
+`get_allocator() == x.get_allocator()` is `true`.
 *Effects:* Inserts the element following `i` into `*this`, following
 `position`, and removes it from `x`. The result is unchanged if
 `position == i` or `position == ++i`. Pointers and references to `*++i`
 continue to refer to the same element but as a member of `*this`.
                   const_iterator first, const_iterator last);
 void splice_after(const_iterator position, forward_list&& x,
                   const_iterator first, const_iterator last);
 ```
+*Preconditions:* `position` is `before_begin()` or is a dereferenceable
 iterator in the range \[`begin()`, `end()`). (`first`, `last`) is a
 valid range in `x`, and all iterators in the range (`first`, `last`) are
 dereferenceable. `position` is not an iterator in the range (`first`,
+`last`). `get_allocator() == x.get_allocator()` is `true`.
 *Effects:* Inserts elements in the range (`first`, `last`) after
 `position` and removes the elements from `x`. Pointers and references to
 the moved elements of `x` now refer to those same elements but as
 members of `*this`. Iterators referring to the moved elements will
 into `*this`, not into `x`.
 *Complexity:* 𝑂(`distance(first, last)`)
 ``` cpp
+size_type remove(const T& value);
+template<class Predicate> size_type remove_if(Predicate pred);
 ```
+*Effects:* Erases all the elements in the list referred to by a list
 iterator `i` for which the following conditions hold: `*i == value` (for
 `remove()`), `pred(*i)` is `true` (for `remove_if()`). Invalidates only
 the iterators and references to the erased elements.
+*Returns:* The number of elements erased.
 *Throws:* Nothing unless an exception is thrown by the equality
 comparison or the predicate.
+*Remarks:* Stable [[algorithm.stable]].
 *Complexity:* Exactly `distance(begin(), end())` applications of the
 corresponding predicate.
 ``` cpp
+size_type unique();
+template<class BinaryPredicate> size_type unique(BinaryPredicate pred);
 ```
 *Effects:* Erases all but the first element from every consecutive group
 of equal elements referred to by the iterator `i` in the range
 \[`first + 1`, `last`) for which `*i == *(i-1)` (for the version with no
 arguments) or `pred(*i, *(i - 1))` (for the version with a predicate
 argument) holds. Invalidates only the iterators and references to the
 erased elements.
+*Returns:* The number of elements erased.
 *Throws:* Nothing unless an exception is thrown by the equality
 comparison or the predicate.
 *Complexity:* If the range \[`first`, `last`) is not empty, exactly
 `(last - first) - 1` applications of the corresponding predicate,
 void merge(forward_list&& x);
 template<class Compare> void merge(forward_list& x, Compare comp);
 template<class Compare> void merge(forward_list&& x, Compare comp);
 ```
+*Preconditions:* `*this` and `x` are both sorted with respect to the
+comparator `operator<` (for the first two overloads) or `comp` (for the
+last two overloads), and `get_allocator() == x.get_allocator()` is
+`true`.
 *Effects:* Merges the two sorted ranges `[begin(), end())` and
 `[x.begin(), x.end())`. `x` is empty after the merge. If an exception is
 thrown other than by a comparison there are no effects. Pointers and
 references to the moved elements of `x` now refer to those same elements
 but as members of `*this`. Iterators referring to the moved elements
 will continue to refer to their elements, but they now behave as
 iterators into `*this`, not into `x`.
+*Remarks:* Stable [[algorithm.stable]].
 *Complexity:* At most
 `distance(begin(), end()) + distance(x.begin(), x.end()) - 1`
 comparisons.
 ``` cpp
 void sort();
 template<class Compare> void sort(Compare comp);
 ```
 *Effects:* Sorts the list according to the `operator<` or the `comp`
 function object. If an exception is thrown, the order of the elements in
 `*this` is unspecified. Does not affect the validity of iterators and
 references.
+*Remarks:* Stable [[algorithm.stable]].
 *Complexity:* Approximately N log N comparisons, where N is
 `distance(begin(), end())`.
 ``` cpp
 *Effects:* Reverses the order of the elements in the list. Does not
 affect the validity of iterators and references.
 *Complexity:* Linear time.
+#### Erasure <a id="forward.list.erasure">[[forward.list.erasure]]</a>
 ``` cpp
+template<class T, class Allocator, class U>
+ typename forward_list<T, Allocator>::size_type
+ erase(forward_list<T, Allocator>& c, const U& value);
 ```
+*Effects:* Equivalent to:
+`return erase_if(c, [&](auto& elem) { return elem == value; });`
+``` cpp
+template<class T, class Allocator, class Predicate>
+  typename forward_list<T, Allocator>::size_type
+    erase_if(forward_list<T, Allocator>& c, Predicate pred);
+```
+*Effects:* Equivalent to: `return c.remove_if(pred);`
 ### Class template `list` <a id="list">[[list]]</a>
+#### Overview <a id="list.overview">[[list.overview]]</a>
 A `list` is a sequence container that supports bidirectional iterators
 and allows constant time insert and erase operations anywhere within the
+sequence, with storage management handled automatically. Unlike vectors
+[[vector]] and deques [[deque]], fast random access to list elements is
+not supported, but many algorithms only need sequential access anyway.
+A `list` meets all of the requirements of a container, of a reversible
+container (given in two tables in [[container.requirements]]), of a
+sequence container, including most of the optional sequence container
+requirements [[sequence.reqmts]], and of an allocator-aware container (
+[[container.alloc.req]]). The exceptions are the `operator[]` and `at`
+member functions, which are not provided.[^2] Descriptions are provided
+here only for operations on `list` that are not described in one of
+these tables or for operations where there is additional semantic
 information.
 ``` cpp
 namespace std {
   template<class T, class Allocator = allocator<T>>
   class list {
   public:
+    // types
     using value_type             = T;
     using allocator_type         = Allocator;
     using pointer                = typename allocator_traits<Allocator>::pointer;
     using const_pointer          = typename allocator_traits<Allocator>::const_pointer;
     using reference              = value_type&;
       void assign(InputIterator first, InputIterator last);
     void assign(size_type n, const T& t);
     void assign(initializer_list<T>);
     allocator_type get_allocator() const noexcept;
+    // iterators
     iterator               begin() noexcept;
     const_iterator         begin() const noexcept;
     iterator               end() noexcept;
     const_iterator         end() const noexcept;
     reverse_iterator       rbegin() noexcept;
     const_iterator         cend() const noexcept;
     const_reverse_iterator crbegin() const noexcept;
     const_reverse_iterator crend() const noexcept;
     // [list.capacity], capacity
+ [[nodiscard]] bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
     void      resize(size_type sz);
     void      resize(size_type sz, const T& c);
+    // element access
     reference       front();
     const_reference front() const;
     reference       back();
     const_reference back() const;
     template<class... Args> iterator emplace(const_iterator position, Args&&... args);
     iterator insert(const_iterator position, const T& x);
     iterator insert(const_iterator position, T&& x);
     iterator insert(const_iterator position, size_type n, const T& x);
     template<class InputIterator>
+      iterator insert(const_iterator position, InputIterator first, InputIterator last);
     iterator insert(const_iterator position, initializer_list<T> il);
     iterator erase(const_iterator position);
     iterator erase(const_iterator position, const_iterator last);
+    void     swap(list&) noexcept(allocator_traits<Allocator>::is_always_equal::value);
     void     clear() noexcept;
     // [list.ops], list operations
     void splice(const_iterator position, list& x);
     void splice(const_iterator position, list&& x);
     void splice(const_iterator position, list& x, const_iterator i);
     void splice(const_iterator position, list&& x, const_iterator i);
+    void splice(const_iterator position, list& x, const_iterator first, const_iterator last);
+    void splice(const_iterator position, list&& x, const_iterator first, const_iterator last);
+ size_type remove(const T& value);
+    template<class Predicate> size_type remove_if(Predicate pred);
+ size_type unique();
     template<class BinaryPredicate>
+ size_type unique(BinaryPredicate binary_pred);
     void merge(list& x);
     void merge(list&& x);
     template<class Compare> void merge(list& x, Compare comp);
     template<class Compare> void merge(list&& x, Compare comp);
     template<class Compare> void sort(Compare comp);
     void reverse() noexcept;
   };
+  template<class InputIterator, class Allocator = allocator<iter-value-type<InputIterator>>>
     list(InputIterator, InputIterator, Allocator = Allocator())
+      -> list<iter-value-type<InputIterator>, Allocator>;
+ // swap
   template<class T, class Allocator>
     void swap(list<T, Allocator>& x, list<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
 An incomplete type `T` may be used when instantiating `list` if the
+allocator meets the allocator completeness requirements
+[[allocator.requirements.completeness]]. `T` shall be complete before
 any member of the resulting specialization of `list` is referenced.
+#### Constructors, copy, and assignment <a id="list.cons">[[list.cons]]</a>
 ``` cpp
 explicit list(const Allocator&);
 ```
 ``` cpp
 explicit list(size_type n, const Allocator& = Allocator());
 ```
+*Preconditions:* `T` is *Cpp17DefaultInsertable* into `*this`.
 *Effects:* Constructs a `list` with `n` default-inserted elements using
 the specified allocator.
 *Complexity:* Linear in `n`.
 ``` cpp
 list(size_type n, const T& value, const Allocator& = Allocator());
 ```
+*Preconditions:* `T` is *Cpp17CopyInsertable* into `*this`.
 *Effects:* Constructs a `list` with `n` copies of `value`, using the
 specified allocator.
 *Complexity:* Linear in `n`.
 ``` cpp
 template<class InputIterator>
   list(InputIterator first, InputIterator last, const Allocator& = Allocator());
 *Effects:* Constructs a `list` equal to the range \[`first`, `last`).
 *Complexity:* Linear in `distance(first, last)`.
+#### Capacity <a id="list.capacity">[[list.capacity]]</a>
 ``` cpp
 void resize(size_type sz);
 ```
+*Preconditions:* `T` is *Cpp17DefaultInsertable* into `*this`.
 *Effects:* If `size() < sz`, appends `sz - size()` default-inserted
 elements to the sequence. If `sz <= size()`, equivalent to:
 ``` cpp
 list<T>::iterator it = begin();
 advance(it, sz);
 erase(it, end());
 ```
 ``` cpp
 void resize(size_type sz, const T& c);
 ```
+*Preconditions:* `T` is *Cpp17CopyInsertable* into `*this`.
 *Effects:* As if by:
 ``` cpp
 if (sz > size())
   insert(end(), sz-size(), c);
 }
 else
   ;                 // do nothing
 ```
+#### Modifiers <a id="list.modifiers">[[list.modifiers]]</a>
 ``` cpp
 iterator insert(const_iterator position, const T& x);
 iterator insert(const_iterator position, T&& x);
 iterator insert(const_iterator position, size_type n, const T& x);
 *Complexity:* Erasing a single element is a constant time operation with
 a single call to the destructor of `T`. Erasing a range in a list is
 linear time in the size of the range and the number of calls to the
 destructor of type `T` is exactly equal to the size of the range.
+#### Operations <a id="list.ops">[[list.ops]]</a>
 Since lists allow fast insertion and erasing from the middle of a list,
+certain operations are provided specifically for them.[^3] In this
+subclause, arguments for a template parameter named `Predicate` or
+`BinaryPredicate` shall meet the corresponding requirements in
+[[algorithms.requirements]]. For `merge` and `sort`, the definitions and
+requirements in [[alg.sorting]] apply.
 `list` provides three splice operations that destructively move elements
 from one list to another. The behavior of splice operations is undefined
 if `get_allocator() !=
 x.get_allocator()`.
 ``` cpp
 void splice(const_iterator position, list& x);
 void splice(const_iterator position, list&& x);
 ```
+*Preconditions:* `addressof(x) != this` is `true`.
 *Effects:* Inserts the contents of `x` before `position` and `x` becomes
 empty. Pointers and references to the moved elements of `x` now refer to
 those same elements but as members of `*this`. Iterators referring to
 the moved elements will continue to refer to their elements, but they
 ``` cpp
 void splice(const_iterator position, list& x, const_iterator i);
 void splice(const_iterator position, list&& x, const_iterator i);
 ```
+*Preconditions:* `i` is a valid dereferenceable iterator of `x`.
 *Effects:* Inserts an element pointed to by `i` from list `x` before
 `position` and removes the element from `x`. The result is unchanged if
 `position == i` or `position == ++i`. Pointers and references to `*i`
 continue to refer to this same element but as a member of `*this`.
             const_iterator last);
 void splice(const_iterator position, list&& x, const_iterator first,
             const_iterator last);
 ```
+*Preconditions:* `[first, last)` is a valid range in `x`. `position` is
+not an iterator in the range \[`first`, `last`).
 *Effects:* Inserts elements in the range \[`first`, `last`) before
 `position` and removes the elements from `x`. Pointers and references to
 the moved elements of `x` now refer to those same elements but as
 members of `*this`. Iterators referring to the moved elements will
 continue to refer to their elements, but they now behave as iterators
 into `*this`, not into `x`.
 *Throws:* Nothing.
+*Complexity:* Constant time if `addressof(x) == this`; otherwise, linear
+time.
 ``` cpp
+size_type remove(const T& value);
+template<class Predicate> size_type remove_if(Predicate pred);
 ```
+*Effects:* Erases all the elements in the list referred to by a list
+iterator `i` for which the following conditions hold: `*i == value`,
+`pred(*i) != false`. Invalidates only the iterators and references to
+the erased elements.
+*Returns:* The number of elements erased.
 *Throws:* Nothing unless an exception is thrown by `*i == value` or
 `pred(*i) != false`.
+*Remarks:* Stable [[algorithm.stable]].
 *Complexity:* Exactly `size()` applications of the corresponding
 predicate.
 ``` cpp
+size_type unique();
+template<class BinaryPredicate> size_type unique(BinaryPredicate binary_pred);
 ```
 *Effects:* Erases all but the first element from every consecutive group
 of equal elements referred to by the iterator `i` in the range
 \[`first + 1`, `last`) for which `*i == *(i-1)` (for the version of
 `unique` with no arguments) or `pred(*i, *(i - 1))` (for the version of
 `unique` with a predicate argument) holds. Invalidates only the
 iterators and references to the erased elements.
+*Returns:* The number of elements erased.
 *Throws:* Nothing unless an exception is thrown by `*i == *(i-1)` or
 `pred(*i, *(i - 1))`
 *Complexity:* If the range `[first, last)` is not empty, exactly
 `(last - first) - 1` applications of the corresponding predicate,
 void merge(list&& x);
 template<class Compare> void merge(list& x, Compare comp);
 template<class Compare> void merge(list&& x, Compare comp);
 ```
+*Preconditions:* Both the list and the argument list shall be sorted
+with respect to the comparator `operator<` (for the first two overloads)
+or `comp` (for the last two overloads), and
+`get_allocator() == x.get_allocator()` is `true`.
+*Effects:* If `addressof(x) == this`, does nothing; otherwise, merges
+the two sorted ranges `[begin(), end())` and `[x.begin(), x.end())`. The
+result is a range in which the elements will be sorted in non-decreasing
+order according to the ordering defined by `comp`; that is, for every
+iterator `i`, in the range other than the first, the condition
 `comp(*i, *(i - 1))` will be `false`. Pointers and references to the
 moved elements of `x` now refer to those same elements but as members of
 `*this`. Iterators referring to the moved elements will continue to
 refer to their elements, but they now behave as iterators into `*this`,
 not into `x`.
+*Remarks:* Stable [[algorithm.stable]]. If `addressof(x) != this`, the
+range `[x.begin(), x.end())` is empty after the merge. No elements are
+copied by this operation.
 *Complexity:* At most `size() + x.size() - 1` applications of `comp` if
+`addressof(x) != this`; otherwise, no applications of `comp` are
+performed. If an exception is thrown other than by a comparison there
+are no effects.
 ``` cpp
 void reverse() noexcept;
 ```
 ``` cpp
 void sort();
 template<class Compare> void sort(Compare comp);
 ```
 *Effects:* Sorts the list according to the `operator<` or a `Compare`
 function object. If an exception is thrown, the order of the elements in
 `*this` is unspecified. Does not affect the validity of iterators and
 references.
+*Remarks:* Stable [[algorithm.stable]].
 *Complexity:* Approximately N log N comparisons, where `N == size()`.
+#### Erasure <a id="list.erasure">[[list.erasure]]</a>
 ``` cpp
+template<class T, class Allocator, class U>
+ typename list<T, Allocator>::size_type
+ erase(list<T, Allocator>& c, const U& value);
 ```
+*Effects:* Equivalent to:
+`return erase_if(c, [&](auto& elem) { return elem == value; });`
+``` cpp
+template<class T, class Allocator, class Predicate>
+  typename list<T, Allocator>::size_type
+    erase_if(list<T, Allocator>& c, Predicate pred);
+```
+*Effects:* Equivalent to: `return c.remove_if(pred);`
 ### Class template `vector` <a id="vector">[[vector]]</a>
+#### Overview <a id="vector.overview">[[vector.overview]]</a>
 A `vector` is a sequence container that supports (amortized) constant
 time insert and erase operations at the end; insert and erase in the
 middle take linear time. Storage management is handled automatically,
 though hints can be given to improve efficiency.
+A `vector` meets all of the requirements of a container and of a
 reversible container (given in two tables in
 [[container.requirements]]), of a sequence container, including most of
+the optional sequence container requirements [[sequence.reqmts]], of an
+allocator-aware container ([[container.alloc.req]]), and, for an
+element type other than `bool`, of a contiguous container
+[[container.requirements.general]]. The exceptions are the `push_front`,
+`pop_front`, and `emplace_front` member functions, which are not
+provided. Descriptions are provided here only for operations on `vector`
+that are not described in one of these tables or for operations where
+there is additional semantic information.
+The types `iterator` and `const_iterator` meet the constexpr iterator
+requirements [[iterator.requirements.general]].
 ``` cpp
 namespace std {
   template<class T, class Allocator = allocator<T>>
   class vector {
   public:
+    // types
     using value_type             = T;
     using allocator_type         = Allocator;
     using pointer                = typename allocator_traits<Allocator>::pointer;
     using const_pointer          = typename allocator_traits<Allocator>::const_pointer;
     using reference              = value_type&;
     using const_iterator         = implementation-defined  // type of vector::const_iterator; // see [container.requirements]
     using reverse_iterator       = std::reverse_iterator<iterator>;
     using const_reverse_iterator = std::reverse_iterator<const_iterator>;
     // [vector.cons], construct/copy/destroy
+ constexpr vector() noexcept(noexcept(Allocator())) : vector(Allocator()) { }
+ constexpr explicit vector(const Allocator&) noexcept;
+ constexpr explicit vector(size_type n, const Allocator& = Allocator());
+ constexpr vector(size_type n, const T& value, const Allocator& = Allocator());
     template<class InputIterator>
+ constexpr vector(InputIterator first, InputIterator last, const Allocator& = Allocator());
+ constexpr vector(const vector& x);
+ constexpr vector(vector&&) noexcept;
+ constexpr vector(const vector&, const Allocator&);
+ constexpr vector(vector&&, const Allocator&);
+ constexpr vector(initializer_list<T>, const Allocator& = Allocator());
+ constexpr ~vector();
+ constexpr vector& operator=(const vector& x);
+ constexpr vector& operator=(vector&& x)
       noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value ||
                allocator_traits<Allocator>::is_always_equal::value);
+ constexpr vector& operator=(initializer_list<T>);
     template<class InputIterator>
+ constexpr void assign(InputIterator first, InputIterator last);
+ constexpr void assign(size_type n, const T& u);
+ constexpr void assign(initializer_list<T>);
+ constexpr allocator_type get_allocator() const noexcept;
+    // iterators
+ constexpr iterator               begin() noexcept;
+ constexpr const_iterator         begin() const noexcept;
+ constexpr iterator               end() noexcept;
+ constexpr const_iterator         end() const noexcept;
+ constexpr reverse_iterator       rbegin() noexcept;
+ constexpr const_reverse_iterator rbegin() const noexcept;
+ constexpr reverse_iterator       rend() noexcept;
+ constexpr const_reverse_iterator rend() const noexcept;
+ constexpr const_iterator         cbegin() const noexcept;
+ constexpr const_iterator         cend() const noexcept;
+ constexpr const_reverse_iterator crbegin() const noexcept;
+ constexpr const_reverse_iterator crend() const noexcept;
     // [vector.capacity], capacity
+ [[nodiscard]] constexpr bool empty() const noexcept;
+ constexpr size_type size() const noexcept;
+ constexpr size_type max_size() const noexcept;
+ constexpr size_type capacity() const noexcept;
+ constexpr void      resize(size_type sz);
+ constexpr void      resize(size_type sz, const T& c);
+ constexpr void      reserve(size_type n);
+ constexpr void      shrink_to_fit();
+    // element access
+ constexpr reference       operator[](size_type n);
+ constexpr const_reference operator[](size_type n) const;
+ constexpr const_reference at(size_type n) const;
+ constexpr reference       at(size_type n);
+ constexpr reference       front();
+ constexpr const_reference front() const;
+ constexpr reference       back();
+ constexpr const_reference back() const;
     // [vector.data], data access
+ constexpr T*       data() noexcept;
+ constexpr const T* data() const noexcept;
     // [vector.modifiers], modifiers
+    template<class... Args> constexpr reference emplace_back(Args&&... args);
+ constexpr void push_back(const T& x);
+ constexpr void push_back(T&& x);
+ constexpr void pop_back();
+    template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args);
+ constexpr iterator insert(const_iterator position, const T& x);
+ constexpr iterator insert(const_iterator position, T&& x);
+ constexpr iterator insert(const_iterator position, size_type n, const T& x);
     template<class InputIterator>
+ constexpr iterator insert(const_iterator position,
+                                InputIterator first, InputIterator last);
+ constexpr iterator insert(const_iterator position, initializer_list<T> il);
+ constexpr iterator erase(const_iterator position);
+ constexpr iterator erase(const_iterator first, const_iterator last);
+    constexpr void     swap(vector&)
       noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value ||
                allocator_traits<Allocator>::is_always_equal::value);
+ constexpr void     clear() noexcept;
   };
+  template<class InputIterator, class Allocator = allocator<iter-value-type<InputIterator>>>
     vector(InputIterator, InputIterator, Allocator = Allocator())
+      -> vector<iter-value-type<InputIterator>, Allocator>;
+  // swap
   template<class T, class Allocator>
+ constexpr void swap(vector<T, Allocator>& x, vector<T, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
 An incomplete type `T` may be used when instantiating `vector` if the
+allocator meets the allocator completeness requirements
+[[allocator.requirements.completeness]]. `T` shall be complete before
 any member of the resulting specialization of `vector` is referenced.
+#### Constructors, copy, and assignment <a id="vector.cons">[[vector.cons]]</a>
 ``` cpp
+constexpr explicit vector(const Allocator&) noexcept;
 ```
 *Effects:* Constructs an empty `vector`, using the specified allocator.
 *Complexity:* Constant.
 ``` cpp
+constexpr explicit vector(size_type n, const Allocator& = Allocator());
 ```
+*Preconditions:* `T` is *Cpp17DefaultInsertable* into `*this`.
 *Effects:* Constructs a `vector` with `n` default-inserted elements
 using the specified allocator.
 *Complexity:* Linear in `n`.
 ``` cpp
+constexpr vector(size_type n, const T& value,
                  const Allocator& = Allocator());
 ```
+*Preconditions:* `T` is *Cpp17CopyInsertable* into `*this`.
 *Effects:* Constructs a `vector` with `n` copies of `value`, using the
 specified allocator.
 *Complexity:* Linear in `n`.
 ``` cpp
 template<class InputIterator>
+ constexpr vector(InputIterator first, InputIterator last,
                    const Allocator& = Allocator());
 ```
 *Effects:* Constructs a `vector` equal to the range \[`first`, `last`),
 using the specified allocator.
 is the distance between `first` and `last`) and no reallocations if
 iterators `first` and `last` are of forward, bidirectional, or random
 access categories. It makes order `N` calls to the copy constructor of
 `T` and order log N reallocations if they are just input iterators.
+#### Capacity <a id="vector.capacity">[[vector.capacity]]</a>
 ``` cpp
+constexpr size_type capacity() const noexcept;
 ```
 *Returns:* The total number of elements that the vector can hold without
 requiring reallocation.
+*Complexity:* Constant time.
 ``` cpp
+constexpr void reserve(size_type n);
 ```
+*Preconditions:* `T` is *Cpp17MoveInsertable* into `*this`.
 *Effects:* A directive that informs a `vector` of a planned change in
 size, so that it can manage the storage allocation accordingly. After
 `reserve()`, `capacity()` is greater or equal to the argument of
 `reserve` if reallocation happens; and equal to the previous value of
 `capacity()` otherwise. Reallocation happens at this point if and only
 if the current capacity is less than the argument of `reserve()`. If an
 exception is thrown other than by the move constructor of a
+non-*Cpp17CopyInsertable* type, there are no effects.
 *Complexity:* It does not change the size of the sequence and takes at
 most linear time in the size of the sequence.
 *Throws:* `length_error` if `n > max_size()`.[^4]
 *Remarks:* Reallocation invalidates all the references, pointers, and
+iterators referring to the elements in the sequence, as well as the
+past-the-end iterator.
+[*Note 1*: If no reallocation happens, they remain
+valid. — *end note*]
+No reallocation shall take place during insertions that happen after a
+call to `reserve()` until an insertion would make the size of the vector
+greater than the value of `capacity()`.
 ``` cpp
+constexpr void shrink_to_fit();
 ```
+*Preconditions:* `T` is *Cpp17MoveInsertable* into `*this`.
 *Effects:* `shrink_to_fit` is a non-binding request to reduce
 `capacity()` to `size()`.
+[*Note 2*: The request is non-binding to allow latitude for
 implementation-specific optimizations. — *end note*]
 It does not increase `capacity()`, but may reduce `capacity()` by
 causing reallocation. If an exception is thrown other than by the move
+constructor of a non-*Cpp17CopyInsertable* `T` there are no effects.
+*Complexity:* If reallocation happens, linear in the size of the
+sequence.
 *Remarks:* Reallocation invalidates all the references, pointers, and
 iterators referring to the elements in the sequence as well as the
+past-the-end iterator.
+[*Note 3*: If no reallocation happens, they remain
+valid. — *end note*]
 ``` cpp
+constexpr void swap(vector& x)
   noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value ||
            allocator_traits<Allocator>::is_always_equal::value);
 ```
 *Effects:* Exchanges the contents and `capacity()` of `*this` with that
 of `x`.
 *Complexity:* Constant time.
 ``` cpp
+constexpr void resize(size_type sz);
 ```
+*Preconditions:* `T` is *Cpp17MoveInsertable* and
+*Cpp17DefaultInsertable* into `*this`.
 *Effects:* If `sz < size()`, erases the last `size() - sz` elements from
 the sequence. Otherwise, appends `sz - size()` default-inserted elements
 to the sequence.
 *Remarks:* If an exception is thrown other than by the move constructor
+of a non-*Cpp17CopyInsertable* `T` there are no effects.
 ``` cpp
+constexpr void resize(size_type sz, const T& c);
 ```
+*Preconditions:* `T` is *Cpp17CopyInsertable* into `*this`.
 *Effects:* If `sz < size()`, erases the last `size() - sz` elements from
 the sequence. Otherwise, appends `sz - size()` copies of `c` to the
 sequence.
 *Remarks:* If an exception is thrown there are no effects.
+#### Data <a id="vector.data">[[vector.data]]</a>
 ``` cpp
+constexpr T*         data() noexcept;
+constexpr const T*   data() const noexcept;
 ```
 *Returns:* A pointer such that \[`data()`, `data() + size()`) is a valid
 range. For a non-empty vector, `data()` `==` `addressof(front())`.
 *Complexity:* Constant time.
+#### Modifiers <a id="vector.modifiers">[[vector.modifiers]]</a>
 ``` cpp
+constexpr iterator insert(const_iterator position, const T& x);
+constexpr iterator insert(const_iterator position, T&& x);
+constexpr iterator insert(const_iterator position, size_type n, const T& x);
 template<class InputIterator>
+ constexpr iterator insert(const_iterator position, InputIterator first, InputIterator last);
+constexpr iterator insert(const_iterator position, initializer_list<T>);
+template<class... Args> constexpr reference emplace_back(Args&&... args);
+template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args);
+constexpr void push_back(const T& x);
+constexpr void push_back(T&& x);
 ```
 *Remarks:* Causes reallocation if the new size is greater than the old
 capacity. Reallocation invalidates all the references, pointers, and
+iterators referring to the elements in the sequence, as well as the
+past-the-end iterator. If no reallocation happens, then references,
+pointers, and iterators before the insertion point remain valid but
+those at or after the insertion point, including the past-the-end
+iterator, are invalidated. If an exception is thrown other than by the
+copy constructor, move constructor, assignment operator, or move
+assignment operator of `T` or by any `InputIterator` operation there are
+no effects. If an exception is thrown while inserting a single element
+at the end and `T` is *Cpp17CopyInsertable* or
 `is_nothrow_move_constructible_v<T>` is `true`, there are no effects.
 Otherwise, if an exception is thrown by the move constructor of a
+non-*Cpp17CopyInsertable* `T`, the effects are unspecified.
+*Complexity:* If reallocation happens, linear in the number of elements
+of the resulting vector; otherwise, linear in the number of elements
 inserted plus the distance to the end of the vector.
 ``` cpp
+constexpr iterator erase(const_iterator position);
+constexpr iterator erase(const_iterator first, const_iterator last);
+constexpr void pop_back();
 ```
 *Effects:* Invalidates iterators and references at or after the point of
 the erase.
 vector after the erased elements.
 *Throws:* Nothing unless an exception is thrown by the assignment
 operator or move assignment operator of `T`.
+#### Erasure <a id="vector.erasure">[[vector.erasure]]</a>
 ``` cpp
+template<class T, class Allocator, class U>
+ constexpr typename vector<T, Allocator>::size_type
+ erase(vector<T, Allocator>& c, const U& value);
 ```
+*Effects:* Equivalent to:
+``` cpp
+auto it = remove(c.begin(), c.end(), value);
+auto r = distance(it, c.end());
+c.erase(it, c.end());
+return r;
+```
+``` cpp
+template<class T, class Allocator, class Predicate>
+  constexpr typename vector<T, Allocator>::size_type
+    erase_if(vector<T, Allocator>& c, Predicate pred);
+```
+*Effects:* Equivalent to:
+``` cpp
+auto it = remove_if(c.begin(), c.end(), pred);
+auto r = distance(it, c.end());
+c.erase(it, c.end());
+return r;
+```
 ### Class `vector<bool>` <a id="vector.bool">[[vector.bool]]</a>
 To optimize space allocation, a specialization of vector for `bool`
 elements is provided:
 ``` cpp
 namespace std {
   template<class Allocator>
   class vector<bool, Allocator> {
   public:
+    // types
     using value_type             = bool;
     using allocator_type         = Allocator;
     using pointer                = implementation-defined;
     using const_pointer          = implementation-defined;
     using const_reference        = bool;
     using iterator               = implementation-defined  // type of vector<bool>::iterator; // see [container.requirements]
     using const_iterator         = implementation-defined  // type of vector<bool>::const_iterator; // see [container.requirements]
     using reverse_iterator       = std::reverse_iterator<iterator>;
     using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+    // bit reference
     class reference {
       friend class vector;
+ constexpr reference() noexcept;
     public:
+ constexpr reference(const reference&) = default;
+ constexpr ~reference();
+ constexpr operator bool() const noexcept;
+ constexpr reference& operator=(const bool x) noexcept;
+ constexpr reference& operator=(const reference& x) noexcept;
+      constexpr void flip() noexcept;   // flips the bit
     };
+    // construct/copy/destroy
+ constexpr vector() : vector(Allocator()) { }
+ constexpr explicit vector(const Allocator&);
+ constexpr explicit vector(size_type n, const Allocator& = Allocator());
+ constexpr vector(size_type n, const bool& value, const Allocator& = Allocator());
     template<class InputIterator>
+ constexpr vector(InputIterator first, InputIterator last, const Allocator& = Allocator());
+    constexpr vector(const vector& x);
+ constexpr vector(vector&& x);
+ constexpr vector(const vector&, const Allocator&);
+ constexpr vector(vector&&, const Allocator&);
+ constexpr vector(initializer_list<bool>, const Allocator& = Allocator()));
+ constexpr ~vector();
+ constexpr vector& operator=(const vector& x);
+ constexpr vector& operator=(vector&& x);
+ constexpr vector& operator=(initializer_list<bool>);
     template<class InputIterator>
+ constexpr void assign(InputIterator first, InputIterator last);
+ constexpr void assign(size_type n, const bool& t);
+ constexpr void assign(initializer_list<bool>);
+ constexpr allocator_type get_allocator() const noexcept;
+    // iterators
+ constexpr iterator               begin() noexcept;
+ constexpr const_iterator         begin() const noexcept;
+ constexpr iterator               end() noexcept;
+ constexpr const_iterator         end() const noexcept;
+ constexpr reverse_iterator       rbegin() noexcept;
+ constexpr const_reverse_iterator rbegin() const noexcept;
+ constexpr reverse_iterator       rend() noexcept;
+ constexpr const_reverse_iterator rend() const noexcept;
+ constexpr const_iterator         cbegin() const noexcept;
+ constexpr const_iterator         cend() const noexcept;
+ constexpr const_reverse_iterator crbegin() const noexcept;
+ constexpr const_reverse_iterator crend() const noexcept;
+    // capacity
+ [[nodiscard]] constexpr bool empty() const noexcept;
+ constexpr size_type size() const noexcept;
+ constexpr size_type max_size() const noexcept;
+ constexpr size_type capacity() const noexcept;
+ constexpr void      resize(size_type sz, bool c = false);
+ constexpr void      reserve(size_type n);
+ constexpr void      shrink_to_fit();
+    // element access
+ constexpr reference       operator[](size_type n);
+ constexpr const_reference operator[](size_type n) const;
+ constexpr const_reference at(size_type n) const;
+ constexpr reference       at(size_type n);
+ constexpr reference       front();
+ constexpr const_reference front() const;
+ constexpr reference       back();
+ constexpr const_reference back() const;
+    // modifiers
+    template<class... Args> constexpr reference emplace_back(Args&&... args);
+ constexpr void push_back(const bool& x);
+ constexpr void pop_back();
+    template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args);
+ constexpr iterator insert(const_iterator position, const bool& x);
+ constexpr iterator insert(const_iterator position, size_type n, const bool& x);
     template<class InputIterator>
+ constexpr iterator insert(const_iterator position,
                                 InputIterator first, InputIterator last);
+ constexpr iterator insert(const_iterator position, initializer_list<bool> il);
+ constexpr iterator erase(const_iterator position);
+ constexpr iterator erase(const_iterator first, const_iterator last);
+ constexpr void swap(vector&);
+ constexpr static void swap(reference x, reference y) noexcept;
+ constexpr void flip() noexcept; // flips all bits
+ constexpr void clear() noexcept;
   };
 }
 ```
 Unless described below, all operations have the same requirements and
 semantics as the primary `vector` template, except that operations
 dealing with the `bool` value type map to bit values in the container
+storage and `allocator_traits::construct` [[allocator.traits.members]]
+is not used to construct these values.
 There is no requirement that the data be stored as a contiguous
 allocation of `bool` values. A space-optimized representation of bits is
 recommended instead.
 set, and `false` otherwise. The assignment operator sets the bit when
 the argument is (convertible to) `true` and clears it otherwise. `flip`
 reverses the state of the bit.
 ``` cpp
+constexpr void flip() noexcept;
 ```
 *Effects:* Replaces each element in the container with its complement.
 ``` cpp
+constexpr static void swap(reference x, reference y) noexcept;
 ```
 *Effects:* Exchanges the contents of `x` and `y` as if by:
 ``` cpp
 ``` cpp
 template<class Allocator> struct hash<vector<bool, Allocator>>;
 ```
+The specialization is enabled [[unord.hash]].
 ## Associative containers <a id="associative">[[associative]]</a>
 ### In general <a id="associative.general">[[associative.general]]</a>
 The following exposition-only alias templates may appear in deduction
 guides for associative containers:
 ``` cpp
 template<class InputIterator>
+  using iter-value-type =
+    typename iterator_traits<InputIterator>::value_type;                // exposition only
+template<class InputIterator>
+  using iter-key-type = remove_const_t<
     typename iterator_traits<InputIterator>::value_type::first_type>;   // exposition only
 template<class InputIterator>
+  using iter-mapped-type =
+    typename iterator_traits<InputIterator>::value_type::second_type; // exposition only
 template<class InputIterator>
+  using iter-to-alloc-type = pair<
+    add_const_t<typename iterator_traits<InputIterator>::value_type::first_type>,
     typename iterator_traits<InputIterator>::value_type::second_type>;  // exposition only
 ```
 ### Header `<map>` synopsis <a id="associative.map.syn">[[associative.map.syn]]</a>
 ``` cpp
+#include <compare>              // see [compare.syn]
+#include <initializer_list>     // see [initializer.list.syn]
 namespace std {
   // [map], class template map
   template<class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T>>>
     class map;
   template<class Key, class T, class Compare, class Allocator>
     bool operator==(const map<Key, T, Compare, Allocator>& x,
                     const map<Key, T, Compare, Allocator>& y);
   template<class Key, class T, class Compare, class Allocator>
+ synth-three-way-result<pair<const Key, T>>
+      operator<=>(const map<Key, T, Compare, Allocator>& x,
                   const map<Key, T, Compare, Allocator>& y);
   template<class Key, class T, class Compare, class Allocator>
     void swap(map<Key, T, Compare, Allocator>& x,
               map<Key, T, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
+  template<class Key, class T, class Compare, class Allocator, class Predicate>
+    typename map<Key, T, Compare, Allocator>::size_type
+      erase_if(map<Key, T, Compare, Allocator>& c, Predicate pred);
   // [multimap], class template multimap
   template<class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T>>>
     class multimap;
   template<class Key, class T, class Compare, class Allocator>
     bool operator==(const multimap<Key, T, Compare, Allocator>& x,
                     const multimap<Key, T, Compare, Allocator>& y);
   template<class Key, class T, class Compare, class Allocator>
+ synth-three-way-result<pair<const Key, T>>
+      operator<=>(const multimap<Key, T, Compare, Allocator>& x,
                   const multimap<Key, T, Compare, Allocator>& y);
   template<class Key, class T, class Compare, class Allocator>
     void swap(multimap<Key, T, Compare, Allocator>& x,
               multimap<Key, T, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
+  template<class Key, class T, class Compare, class Allocator, class Predicate>
+    typename multimap<Key, T, Compare, Allocator>::size_type
+      erase_if(multimap<Key, T, Compare, Allocator>& c, Predicate pred);
   namespace pmr {
     template<class Key, class T, class Compare = less<Key>>
       using map = std::map<Key, T, Compare,
                            polymorphic_allocator<pair<const Key, T>>>;
 ```
 ### Header `<set>` synopsis <a id="associative.set.syn">[[associative.set.syn]]</a>
 ``` cpp
+#include <compare>              // see [compare.syn]
+#include <initializer_list>     // see [initializer.list.syn]
 namespace std {
   // [set], class template set
+  template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
     class set;
   template<class Key, class Compare, class Allocator>
     bool operator==(const set<Key, Compare, Allocator>& x,
                     const set<Key, Compare, Allocator>& y);
   template<class Key, class Compare, class Allocator>
+ synth-three-way-result<Key> operator<=>(const set<Key, Compare, Allocator>& x,
+    \itcorr                                        const set<Key, Compare, Allocator>& y);
   template<class Key, class Compare, class Allocator>
     void swap(set<Key, Compare, Allocator>& x,
               set<Key, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
+  template<class Key, class Compare, class Allocator, class Predicate>
+    typename set<Key, Compare, Allocator>::size_type
+      erase_if(set<Key, Compare, Allocator>& c, Predicate pred);
   // [multiset], class template multiset
+  template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
     class multiset;
   template<class Key, class Compare, class Allocator>
     bool operator==(const multiset<Key, Compare, Allocator>& x,
                     const multiset<Key, Compare, Allocator>& y);
   template<class Key, class Compare, class Allocator>
+ synth-three-way-result<Key> operator<=>(const multiset<Key, Compare, Allocator>& x,
+    \itcorr                                        const multiset<Key, Compare, Allocator>& y);
   template<class Key, class Compare, class Allocator>
     void swap(multiset<Key, Compare, Allocator>& x,
               multiset<Key, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
+  template<class Key, class Compare, class Allocator, class Predicate>
+    typename multiset<Key, Compare, Allocator>::size_type
+      erase_if(multiset<Key, Compare, Allocator>& c, Predicate pred);
   namespace pmr {
     template<class Key, class Compare = less<Key>>
+      using set = std::set<Key, Compare, polymorphic_allocator<Key>>;
     template<class Key, class Compare = less<Key>>
+      using multiset = std::multiset<Key, Compare, polymorphic_allocator<Key>>;
   }
 }
 ```
 ### Class template `map` <a id="map">[[map]]</a>
+#### Overview <a id="map.overview">[[map.overview]]</a>
 A `map` is an associative container that supports unique keys (contains
 at most one of each key value) and provides for fast retrieval of values
 of another type `T` based on the keys. The `map` class supports
 bidirectional iterators.
+A `map` meets all of the requirements of a container, of a reversible
+container [[container.requirements]], of an associative container
+[[associative.reqmts]], and of an allocator-aware container (
+[[container.alloc.req]]). A `map` also provides most operations
+described in  [[associative.reqmts]] for unique keys. This means that a
+`map` supports the `a_uniq` operations in  [[associative.reqmts]] but
+not the `a_eq` operations. For a `map<Key,T>` the `key_type` is `Key`
+and the `value_type` is `pair<const Key,T>`. Descriptions are provided
+here only for operations on `map` that are not described in one of those
+tables or for operations where there is additional semantic information.
 ``` cpp
 namespace std {
   template<class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T>>>
   class map {
   public:
+    // types
     using key_type               = Key;
     using mapped_type            = T;
     using value_type             = pair<const Key, T>;
     using key_compare            = Compare;
     using allocator_type         = Allocator;
     using iterator               = implementation-defined  // type of map::iterator; // see [container.requirements]
     using const_iterator         = implementation-defined  // type of map::const_iterator; // see [container.requirements]
     using reverse_iterator       = std::reverse_iterator<iterator>;
     using const_reverse_iterator = std::reverse_iterator<const_iterator>;
     using node_type              = unspecified;
+    using insert_return_type     = insert-return-type<iterator, node_type>;
     class value_compare {
       friend class map;
     protected:
       Compare comp;
       noexcept(allocator_traits<Allocator>::is_always_equal::value &&
                is_nothrow_move_assignable_v<Compare>);
     map& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
+    // iterators
     iterator               begin() noexcept;
     const_iterator         begin() const noexcept;
     iterator               end() noexcept;
     const_iterator         end() const noexcept;
     const_iterator         cbegin() const noexcept;
     const_iterator         cend() const noexcept;
     const_reverse_iterator crbegin() const noexcept;
     const_reverse_iterator crend() const noexcept;
+    // capacity
+ [[nodiscard]] bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
     // [map.access], element access
+ mapped_type& operator[](const key_type& x);
+ mapped_type& operator[](key_type&& x);
+ mapped_type&       at(const key_type& x);
+    const mapped_type& at(const key_type& x) const;
     // [map.modifiers], modifiers
     template<class... Args> pair<iterator, bool> emplace(Args&&... args);
     template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
     pair<iterator, bool> insert(const value_type& x);
     template<class C2>
       void merge(multimap<Key, T, C2, Allocator>& source);
     template<class C2>
       void merge(multimap<Key, T, C2, Allocator>&& source);
+    // observers
     key_compare key_comp() const;
     value_compare value_comp() const;
+    // map operations
     iterator       find(const key_type& x);
     const_iterator find(const key_type& x) const;
     template<class K> iterator       find(const K& x);
     template<class K> const_iterator find(const K& x) const;
     size_type      count(const key_type& x) const;
     template<class K> size_type count(const K& x) const;
+    bool           contains(const key_type& x) const;
+    template<class K> bool contains(const K& x) const;
     iterator       lower_bound(const key_type& x);
     const_iterator lower_bound(const key_type& x) const;
     template<class K> iterator       lower_bound(const K& x);
     template<class K> const_iterator lower_bound(const K& x) const;
       pair<iterator, iterator>             equal_range(const K& x);
     template<class K>
       pair<const_iterator, const_iterator> equal_range(const K& x) const;
   };
+  template<class InputIterator, class Compare = less<iter-key-type<InputIterator>>,
+           class Allocator = allocator<iter-to-alloc-type<InputIterator>>>
     map(InputIterator, InputIterator, Compare = Compare(), Allocator = Allocator())
+      -> map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>, Compare, Allocator>;
   template<class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T>>>
+    map(initializer_list<pair<Key, T>>, Compare = Compare(), Allocator = Allocator())
       -> map<Key, T, Compare, Allocator>;
   template<class InputIterator, class Allocator>
     map(InputIterator, InputIterator, Allocator)
+      -> map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+             less<iter-key-type<InputIterator>>, Allocator>;
   template<class Key, class T, class Allocator>
+    map(initializer_list<pair<Key, T>>, Allocator) -> map<Key, T, less<Key>, Allocator>;
+ // swap
   template<class Key, class T, class Compare, class Allocator>
     void swap(map<Key, T, Compare, Allocator>& x,
               map<Key, T, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
+#### Constructors, copy, and assignment <a id="map.cons">[[map.cons]]</a>
 ``` cpp
 explicit map(const Compare& comp, const Allocator& = Allocator());
 ```
 `last`).
 *Complexity:* Linear in N if the range \[`first`, `last`) is already
 sorted using `comp` and otherwise N log N, where N is `last - first`.
+#### Element access <a id="map.access">[[map.access]]</a>
 ``` cpp
+mapped_type& operator[](const key_type& x);
 ```
 *Effects:* Equivalent to: `return try_emplace(x).first->second;`
 ``` cpp
+mapped_type& operator[](key_type&& x);
 ```
 *Effects:* Equivalent to: `return try_emplace(move(x)).first->second;`
 ``` cpp
+mapped_type&       at(const key_type& x);
+const mapped_type& at(const key_type& x) const;
 ```
 *Returns:* A reference to the `mapped_type` corresponding to `x` in
 `*this`.
 *Throws:* An exception object of type `out_of_range` if no such element
 is present.
 *Complexity:* Logarithmic.
+#### Modifiers <a id="map.modifiers">[[map.modifiers]]</a>
 ``` cpp
 template<class P>
   pair<iterator, bool> insert(P&& x);
 template<class P>
   iterator insert(const_iterator position, P&& x);
 ```
+*Constraints:* `is_constructible_v<value_type, P&&>` is `true`.
 *Effects:* The first form is equivalent to
 `return emplace(std::forward<P>(x))`. The second form is equivalent to
 `return emplace_hint(position, std::forward<P>(x))`.
 ``` cpp
 template<class... Args>
   pair<iterator, bool> try_emplace(const key_type& k, Args&&... args);
 template<class... Args>
   iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args);
 ```
+*Preconditions:* `value_type` is *Cpp17EmplaceConstructible* into `map`
+from `piecewise_construct`, `forward_as_tuple(k)`,
 `forward_as_tuple(std::forward<Args>(args)...)`.
 *Effects:* If the map already contains an element whose key is
 equivalent to `k`, there is no effect. Otherwise inserts an object of
 type `value_type` constructed with `piecewise_construct`,
   pair<iterator, bool> try_emplace(key_type&& k, Args&&... args);
 template<class... Args>
   iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args);
 ```
+*Preconditions:* `value_type` is *Cpp17EmplaceConstructible* into `map`
+from `piecewise_construct`, `forward_as_tuple(std::move(k))`,
 `forward_as_tuple(std::forward<Args>(args)...)`.
 *Effects:* If the map already contains an element whose key is
 equivalent to `k`, there is no effect. Otherwise inserts an object of
 type `value_type` constructed with `piecewise_construct`,
   pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj);
 template<class M>
   iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj);
 ```
+*Mandates:* `is_assignable_v<mapped_type&, M&&>` is `true`.
+*Preconditions:* `value_type` is *Cpp17EmplaceConstructible* into `map`
+from `k`, `forward<M>(obj)`.
 *Effects:* If the map already contains an element `e` whose key is
 equivalent to `k`, assigns `std::forward<M>(obj)` to `e.second`.
 Otherwise inserts an object of type `value_type` constructed with `k`,
 `std::forward<M>(obj)`.
   pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj);
 template<class M>
   iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj);
 ```
+*Mandates:* `is_assignable_v<mapped_type&, M&&>` is `true`.
+*Preconditions:* `value_type` is *Cpp17EmplaceConstructible* into `map`
+from `move(k)`, `forward<M>(obj)`.
 *Effects:* If the map already contains an element `e` whose key is
 equivalent to `k`, assigns `std::forward<M>(obj)` to `e.second`.
 Otherwise inserts an object of type `value_type` constructed with
 `std::move(k)`, `std::forward<M>(obj)`.
 pair is `true` if and only if the insertion took place. The returned
 iterator points to the map element whose key is equivalent to `k`.
 *Complexity:* The same as `emplace` and `emplace_hint`, respectively.
+#### Erasure <a id="map.erasure">[[map.erasure]]</a>
 ``` cpp
+template<class Key, class T, class Compare, class Allocator, class Predicate>
+ typename map<Key, T, Compare, Allocator>::size_type
+    erase_if(map<Key, T, Compare, Allocator>& c, Predicate pred);
 ```
+*Effects:* Equivalent to:
+``` cpp
+auto original_size = c.size();
+for (auto i = c.begin(), last = c.end(); i != last; ) {
+  if (pred(*i)) {
+    i = c.erase(i);
+  } else {
+    ++i;
+  }
+}
+return original_size - c.size();
+```
 ### Class template `multimap` <a id="multimap">[[multimap]]</a>
+#### Overview <a id="multimap.overview">[[multimap.overview]]</a>
 A `multimap` is an associative container that supports equivalent keys
 (possibly containing multiple copies of the same key value) and provides
 for fast retrieval of values of another type `T` based on the keys. The
 `multimap` class supports bidirectional iterators.
+A `multimap` meets all of the requirements of a container and of a
+reversible container [[container.requirements]], of an associative
+container [[associative.reqmts]], and of an allocator-aware container (
+[[container.alloc.req]]). A `multimap` also provides most operations
+described in  [[associative.reqmts]] for equal keys. This means that a
+`multimap` supports the `a_eq` operations in  [[associative.reqmts]] but
+not the `a_uniq` operations. For a `multimap<Key,T>` the `key_type` is
+`Key` and the `value_type` is `pair<const Key,T>`. Descriptions are
+provided here only for operations on `multimap` that are not described
+in one of those tables or for operations where there is additional
+semantic information.
 ``` cpp
 namespace std {
   template<class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T>>>
   class multimap {
   public:
+    // types
     using key_type               = Key;
     using mapped_type            = T;
     using value_type             = pair<const Key, T>;
     using key_compare            = Compare;
     using allocator_type         = Allocator;
       noexcept(allocator_traits<Allocator>::is_always_equal::value &&
                is_nothrow_move_assignable_v<Compare>);
     multimap& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
+    // iterators
     iterator               begin() noexcept;
     const_iterator         begin() const noexcept;
     iterator               end() noexcept;
     const_iterator         end() const noexcept;
     const_iterator         cbegin() const noexcept;
     const_iterator         cend() const noexcept;
     const_reverse_iterator crbegin() const noexcept;
     const_reverse_iterator crend() const noexcept;
+    // capacity
+ [[nodiscard]] bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
     // [multimap.modifiers], modifiers
     template<class... Args> iterator emplace(Args&&... args);
     template<class C2>
       void merge(map<Key, T, C2, Allocator>& source);
     template<class C2>
       void merge(map<Key, T, C2, Allocator>&& source);
+    // observers
     key_compare key_comp() const;
     value_compare value_comp() const;
+    // map operations
     iterator       find(const key_type& x);
     const_iterator find(const key_type& x) const;
     template<class K> iterator       find(const K& x);
     template<class K> const_iterator find(const K& x) const;
     size_type      count(const key_type& x) const;
     template<class K> size_type count(const K& x) const;
+    bool           contains(const key_type& x) const;
+    template<class K> bool contains(const K& x) const;
     iterator       lower_bound(const key_type& x);
     const_iterator lower_bound(const key_type& x) const;
     template<class K> iterator       lower_bound(const K& x);
     template<class K> const_iterator lower_bound(const K& x) const;
       pair<iterator, iterator>             equal_range(const K& x);
     template<class K>
       pair<const_iterator, const_iterator> equal_range(const K& x) const;
   };
+  template<class InputIterator, class Compare = less<iter-key-type<InputIterator>>,
+           class Allocator = allocator<iter-to-alloc-type<InputIterator>>>
     multimap(InputIterator, InputIterator, Compare = Compare(), Allocator = Allocator())
+      -> multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+                  Compare, Allocator>;
   template<class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T>>>
+    multimap(initializer_list<pair<Key, T>>, Compare = Compare(), Allocator = Allocator())
       -> multimap<Key, T, Compare, Allocator>;
   template<class InputIterator, class Allocator>
     multimap(InputIterator, InputIterator, Allocator)
+      -> multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+                  less<iter-key-type<InputIterator>>, Allocator>;
   template<class Key, class T, class Allocator>
+    multimap(initializer_list<pair<Key, T>>, Allocator)
       -> multimap<Key, T, less<Key>, Allocator>;
+ // swap
   template<class Key, class T, class Compare, class Allocator>
     void swap(multimap<Key, T, Compare, Allocator>& x,
               multimap<Key, T, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
+#### Constructors <a id="multimap.cons">[[multimap.cons]]</a>
 ``` cpp
 explicit multimap(const Compare& comp, const Allocator& = Allocator());
 ```
 `last`).
 *Complexity:* Linear in N if the range \[`first`, `last`) is already
 sorted using `comp` and otherwise N log N, where N is `last - first`.
+#### Modifiers <a id="multimap.modifiers">[[multimap.modifiers]]</a>
 ``` cpp
 template<class P> iterator insert(P&& x);
 template<class P> iterator insert(const_iterator position, P&& x);
 ```
+*Constraints:* `is_constructible_v<value_type, P&&>` is `true`.
 *Effects:* The first form is equivalent to
 `return emplace(std::forward<P>(x))`. The second form is equivalent to
 `return emplace_hint(position, std::forward<P>(x))`.
+#### Erasure <a id="multimap.erasure">[[multimap.erasure]]</a>
 ``` cpp
+template<class Key, class T, class Compare, class Allocator, class Predicate>
+ typename multimap<Key, T, Compare, Allocator>::size_type
+    erase_if(multimap<Key, T, Compare, Allocator>& c, Predicate pred);
 ```
+*Effects:* Equivalent to:
+``` cpp
+auto original_size = c.size();
+for (auto i = c.begin(), last = c.end(); i != last; ) {
+  if (pred(*i)) {
+    i = c.erase(i);
+  } else {
+    ++i;
+  }
+}
+return original_size - c.size();
+```
 ### Class template `set` <a id="set">[[set]]</a>
+#### Overview <a id="set.overview">[[set.overview]]</a>
 A `set` is an associative container that supports unique keys (contains
 at most one of each key value) and provides for fast retrieval of the
 keys themselves. The `set` class supports bidirectional iterators.
+A `set` meets all of the requirements of a container, of a reversible
+container [[container.requirements]], of an associative container
+[[associative.reqmts]], and of an allocator-aware container (
+[[container.alloc.req]]). A `set` also provides most operations
+described in  [[associative.reqmts]] for unique keys. This means that a
+`set` supports the `a_uniq` operations in  [[associative.reqmts]] but
+not the `a_eq` operations. For a `set<Key>` both the `key_type` and
+`value_type` are `Key`. Descriptions are provided here only for
+operations on `set` that are not described in one of these tables and
+for operations where there is additional semantic information.
 ``` cpp
 namespace std {
   template<class Key, class Compare = less<Key>,
            class Allocator = allocator<Key>>
   class set {
   public:
+    // types
     using key_type               = Key;
     using key_compare            = Compare;
     using value_type             = Key;
     using value_compare          = Compare;
     using allocator_type         = Allocator;
     using iterator               = implementation-defined  // type of set::iterator; // see [container.requirements]
     using const_iterator         = implementation-defined  // type of set::const_iterator; // see [container.requirements]
     using reverse_iterator       = std::reverse_iterator<iterator>;
     using const_reverse_iterator = std::reverse_iterator<const_iterator>;
     using node_type              = unspecified;
+    using insert_return_type     = insert-return-type<iterator, node_type>;
     // [set.cons], construct/copy/destroy
     set() : set(Compare()) { }
     explicit set(const Compare& comp, const Allocator& = Allocator());
     template<class InputIterator>
       noexcept(allocator_traits<Allocator>::is_always_equal::value &&
                is_nothrow_move_assignable_v<Compare>);
     set& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
+    // iterators
     iterator               begin() noexcept;
     const_iterator         begin() const noexcept;
     iterator               end() noexcept;
     const_iterator         end() const noexcept;
     const_iterator         cbegin() const noexcept;
     const_iterator         cend() const noexcept;
     const_reverse_iterator crbegin() const noexcept;
     const_reverse_iterator crend() const noexcept;
+    // capacity
+ [[nodiscard]] bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
+    // modifiers
     template<class... Args> pair<iterator, bool> emplace(Args&&... args);
     template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
     pair<iterator,bool> insert(const value_type& x);
     pair<iterator,bool> insert(value_type&& x);
     iterator insert(const_iterator position, const value_type& x);
     template<class C2>
       void merge(multiset<Key, C2, Allocator>& source);
     template<class C2>
       void merge(multiset<Key, C2, Allocator>&& source);
+    // observers
     key_compare key_comp() const;
     value_compare value_comp() const;
+    // set operations
     iterator       find(const key_type& x);
     const_iterator find(const key_type& x) const;
     template<class K> iterator       find(const K& x);
     template<class K> const_iterator find(const K& x) const;
     size_type      count(const key_type& x) const;
     template<class K> size_type count(const K& x) const;
+    bool           contains(const key_type& x) const;
+    template<class K> bool contains(const K& x) const;
     iterator       lower_bound(const key_type& x);
     const_iterator lower_bound(const key_type& x) const;
     template<class K> iterator       lower_bound(const K& x);
     template<class K> const_iterator lower_bound(const K& x) const;
     template<class K>
       pair<const_iterator, const_iterator> equal_range(const K& x) const;
   };
   template<class InputIterator,
+           class Compare = less<iter-value-type<InputIterator>>,
+           class Allocator = allocator<iter-value-type<InputIterator>>>
     set(InputIterator, InputIterator,
         Compare = Compare(), Allocator = Allocator())
+      -> set<iter-value-type<InputIterator>, Compare, Allocator>;
   template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
     set(initializer_list<Key>, Compare = Compare(), Allocator = Allocator())
       -> set<Key, Compare, Allocator>;
   template<class InputIterator, class Allocator>
     set(InputIterator, InputIterator, Allocator)
+      -> set<iter-value-type<InputIterator>,
+             less<iter-value-type<InputIterator>>, Allocator>;
   template<class Key, class Allocator>
     set(initializer_list<Key>, Allocator) -> set<Key, less<Key>, Allocator>;
+ // swap
   template<class Key, class Compare, class Allocator>
     void swap(set<Key, Compare, Allocator>& x,
               set<Key, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
+#### Constructors, copy, and assignment <a id="set.cons">[[set.cons]]</a>
 ``` cpp
 explicit set(const Compare& comp, const Allocator& = Allocator());
 ```
 `last`).
 *Complexity:* Linear in N if the range \[`first`, `last`) is already
 sorted using `comp` and otherwise N log N, where N is `last - first`.
+#### Erasure <a id="set.erasure">[[set.erasure]]</a>
 ``` cpp
+template<class Key, class Compare, class Allocator, class Predicate>
+ typename set<Key, Compare, Allocator>::size_type
+    erase_if(set<Key, Compare, Allocator>& c, Predicate pred);
 ```
+*Effects:* Equivalent to:
+``` cpp
+auto original_size = c.size();
+for (auto i = c.begin(), last = c.end(); i != last; ) {
+  if (pred(*i)) {
+    i = c.erase(i);
+  } else {
+    ++i;
+  }
+}
+return original_size - c.size();
+```
 ### Class template `multiset` <a id="multiset">[[multiset]]</a>
+#### Overview <a id="multiset.overview">[[multiset.overview]]</a>
 A `multiset` is an associative container that supports equivalent keys
 (possibly contains multiple copies of the same key value) and provides
 for fast retrieval of the keys themselves. The `multiset` class supports
 bidirectional iterators.
+A `multiset` meets all of the requirements of a container, of a
+reversible container [[container.requirements]], of an associative
+container [[associative.reqmts]], and of an allocator-aware container (
+[[container.alloc.req]]). `multiset` also provides most operations
+described in  [[associative.reqmts]] for duplicate keys. This means that
+a `multiset` supports the `a_eq` operations in  [[associative.reqmts]]
+but not the `a_uniq` operations. For a `multiset<Key>` both the
+`key_type` and `value_type` are `Key`. Descriptions are provided here
+only for operations on `multiset` that are not described in one of these
+tables and for operations where there is additional semantic
+information.
 ``` cpp
 namespace std {
   template<class Key, class Compare = less<Key>,
            class Allocator = allocator<Key>>
   class multiset {
   public:
+    // types
     using key_type               = Key;
     using key_compare            = Compare;
     using value_type             = Key;
     using value_compare          = Compare;
     using allocator_type         = Allocator;
       noexcept(allocator_traits<Allocator>::is_always_equal::value &&
                is_nothrow_move_assignable_v<Compare>);
     multiset& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
+    // iterators
     iterator               begin() noexcept;
     const_iterator         begin() const noexcept;
     iterator               end() noexcept;
     const_iterator         end() const noexcept;
     const_iterator         cbegin() const noexcept;
     const_iterator         cend() const noexcept;
     const_reverse_iterator crbegin() const noexcept;
     const_reverse_iterator crend() const noexcept;
+    // capacity
+ [[nodiscard]] bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
+    // modifiers
     template<class... Args> iterator emplace(Args&&... args);
     template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
     iterator insert(const value_type& x);
     iterator insert(value_type&& x);
     iterator insert(const_iterator position, const value_type& x);
     template<class C2>
       void merge(set<Key, C2, Allocator>& source);
     template<class C2>
       void merge(set<Key, C2, Allocator>&& source);
+    // observers
     key_compare key_comp() const;
     value_compare value_comp() const;
+    // set operations
     iterator       find(const key_type& x);
     const_iterator find(const key_type& x) const;
     template<class K> iterator       find(const K& x);
     template<class K> const_iterator find(const K& x) const;
     size_type      count(const key_type& x) const;
     template<class K> size_type count(const K& x) const;
+    bool           contains(const key_type& x) const;
+    template<class K> bool contains(const K& x) const;
     iterator       lower_bound(const key_type& x);
     const_iterator lower_bound(const key_type& x) const;
     template<class K> iterator       lower_bound(const K& x);
     template<class K> const_iterator lower_bound(const K& x) const;
     template<class K>
       pair<const_iterator, const_iterator> equal_range(const K& x) const;
   };
   template<class InputIterator,
+           class Compare = less<iter-value-type<InputIterator>>,
+           class Allocator = allocator<iter-value-type<InputIterator>>>
     multiset(InputIterator, InputIterator,
              Compare = Compare(), Allocator = Allocator())
+      -> multiset<iter-value-type<InputIterator>, Compare, Allocator>;
   template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
     multiset(initializer_list<Key>, Compare = Compare(), Allocator = Allocator())
       -> multiset<Key, Compare, Allocator>;
   template<class InputIterator, class Allocator>
     multiset(InputIterator, InputIterator, Allocator)
+      -> multiset<iter-value-type<InputIterator>,
+                  less<iter-value-type<InputIterator>>, Allocator>;
   template<class Key, class Allocator>
     multiset(initializer_list<Key>, Allocator) -> multiset<Key, less<Key>, Allocator>;
+ // swap
   template<class Key, class Compare, class Allocator>
     void swap(multiset<Key, Compare, Allocator>& x,
               multiset<Key, Compare, Allocator>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
+#### Constructors <a id="multiset.cons">[[multiset.cons]]</a>
 ``` cpp
 explicit multiset(const Compare& comp, const Allocator& = Allocator());
 ```
 `last`).
 *Complexity:* Linear in N if the range \[`first`, `last`) is already
 sorted using `comp` and otherwise N log N, where N is `last - first`.
+#### Erasure <a id="multiset.erasure">[[multiset.erasure]]</a>
 ``` cpp
+template<class Key, class Compare, class Allocator, class Predicate>
+ typename multiset<Key, Compare, Allocator>::size_type
+    erase_if(multiset<Key, Compare, Allocator>& c, Predicate pred);
 ```
+*Effects:* Equivalent to:
+``` cpp
+auto original_size = c.size();
+for (auto i = c.begin(), last = c.end(); i != last; ) {
+  if (pred(*i)) {
+    i = c.erase(i);
+  } else {
+    ++i;
+  }
+}
+return original_size - c.size();
+```
 ## Unordered associative containers <a id="unord">[[unord]]</a>
 ### In general <a id="unord.general">[[unord.general]]</a>
 The header `<unordered_map>` defines the class templates `unordered_map`
 and `unordered_multimap`; the header `<unordered_set>` defines the class
 templates `unordered_set` and `unordered_multiset`.
+The exposition-only alias templates *`iter-value-type`*,
+*`iter-key-type`*, *`iter-mapped-type`*, and *`iter-to-alloc-type`*
+defined in [[associative.general]] may appear in deduction guides for
+unordered containers.
 ### Header `<unordered_map>` synopsis <a id="unord.map.syn">[[unord.map.syn]]</a>
 ``` cpp
+#include <compare>              // see [compare.syn]
+#include <initializer_list>     // see [initializer.list.syn]
 namespace std {
   // [unord.map], class template unordered_map
   template<class Key,
            class T,
            class Hash = hash<Key>,
            class Pred = equal_to<Key>,
            class Alloc = allocator<pair<const Key, T>>>
     class unordered_multimap;
+  template<class Key, class T, class Hash, class Pred, class Alloc>
+    bool operator==(const unordered_map<Key, T, Hash, Pred, Alloc>& a,
+                    const unordered_map<Key, T, Hash, Pred, Alloc>& b);
+  template<class Key, class T, class Hash, class Pred, class Alloc>
+    bool operator==(const unordered_multimap<Key, T, Hash, Pred, Alloc>& a,
+                    const unordered_multimap<Key, T, Hash, Pred, Alloc>& b);
   template<class Key, class T, class Hash, class Pred, class Alloc>
     void swap(unordered_map<Key, T, Hash, Pred, Alloc>& x,
               unordered_map<Key, T, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
   template<class Key, class T, class Hash, class Pred, class Alloc>
     void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x,
               unordered_multimap<Key, T, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
+  template<class K, class T, class H, class P, class A, class Predicate>
+ typename unordered_map<K, T, H, P, A>::size_type
+      erase_if(unordered_map<K, T, H, P, A>& c, Predicate pred);
+  template<class K, class T, class H, class P, class A, class Predicate>
+    typename unordered_multimap<K, T, H, P, A>::size_type
+      erase_if(unordered_multimap<K, T, H, P, A>& c, Predicate pred);
   namespace pmr {
     template<class Key,
              class T,
              class Hash = hash<Key>,
 ```
 ### Header `<unordered_set>` synopsis <a id="unord.set.syn">[[unord.set.syn]]</a>
 ``` cpp
+#include <compare>              // see [compare.syn]
+#include <initializer_list>     // see [initializer.list.syn]
 namespace std {
   // [unord.set], class template unordered_set
   template<class Key,
            class Hash = hash<Key>,
            class Hash = hash<Key>,
            class Pred = equal_to<Key>,
            class Alloc = allocator<Key>>
     class unordered_multiset;
+  template<class Key, class Hash, class Pred, class Alloc>
+    bool operator==(const unordered_set<Key, Hash, Pred, Alloc>& a,
+                    const unordered_set<Key, Hash, Pred, Alloc>& b);
+  template<class Key, class Hash, class Pred, class Alloc>
+    bool operator==(const unordered_multiset<Key, Hash, Pred, Alloc>& a,
+                    const unordered_multiset<Key, Hash, Pred, Alloc>& b);
   template<class Key, class Hash, class Pred, class Alloc>
     void swap(unordered_set<Key, Hash, Pred, Alloc>& x,
               unordered_set<Key, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
   template<class Key, class Hash, class Pred, class Alloc>
     void swap(unordered_multiset<Key, Hash, Pred, Alloc>& x,
               unordered_multiset<Key, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
+  template<class K, class H, class P, class A, class Predicate>
+ typename unordered_set<K, H, P, A>::size_type
+      erase_if(unordered_set<K, H, P, A>& c, Predicate pred);
+  template<class K, class H, class P, class A, class Predicate>
+    typename unordered_multiset<K, H, P, A>::size_type
+      erase_if(unordered_multiset<K, H, P, A>& c, Predicate pred);
   namespace pmr {
     template<class Key,
              class Hash = hash<Key>,
              class Pred = equal_to<Key>>
 }
 ```
 ### Class template `unordered_map` <a id="unord.map">[[unord.map]]</a>
+#### Overview <a id="unord.map.overview">[[unord.map.overview]]</a>
 An `unordered_map` is an unordered associative container that supports
 unique keys (an `unordered_map` contains at most one of each key value)
 and that associates values of another type `mapped_type` with the keys.
 The `unordered_map` class supports forward iterators.
+An `unordered_map` meets all of the requirements of a container, of an
+unordered associative container, and of an allocator-aware container (
+[[container.alloc.req]]). It provides the operations described in the
+preceding requirements table for unique keys; that is, an
+`unordered_map` supports the `a_uniq` operations in that table, not the
+`a_eq` operations. For an `unordered_map<Key, T>` the `key type` is
 `Key`, the mapped type is `T`, and the value type is
 `pair<const Key, T>`.
+Subclause  [[unord.map]] only describes operations on `unordered_map`
+that are not described in one of the requirement tables, or for which
+there is additional semantic information.
 ``` cpp
 namespace std {
   template<class Key,
            class T,
            class Hash = hash<Key>,
            class Pred = equal_to<Key>,
            class Allocator = allocator<pair<const Key, T>>>
   class unordered_map {
   public:
+    // types
     using key_type             = Key;
     using mapped_type          = T;
     using value_type           = pair<const Key, T>;
     using hasher               = Hash;
     using key_equal            = Pred;
     using iterator             = implementation-defined  // type of unordered_map::iterator; // see [container.requirements]
     using const_iterator       = implementation-defined  // type of unordered_map::const_iterator; // see [container.requirements]
     using local_iterator       = implementation-defined  // type of unordered_map::local_iterator; // see [container.requirements]
     using const_local_iterator = implementation-defined  // type of unordered_map::const_local_iterator; // see [container.requirements]
     using node_type            = unspecified;
+    using insert_return_type   = insert-return-type<iterator, node_type>;
     // [unord.map.cnstr], construct/copy/destroy
     unordered_map();
     explicit unordered_map(size_type n,
                            const hasher& hf = hasher(),
                is_nothrow_move_assignable_v<Hash> &&
                is_nothrow_move_assignable_v<Pred>);
     unordered_map& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
+    // iterators
     iterator       begin() noexcept;
     const_iterator begin() const noexcept;
     iterator       end() noexcept;
     const_iterator end() const noexcept;
     const_iterator cbegin() const noexcept;
     const_iterator cend() const noexcept;
+    // capacity
+ [[nodiscard]] bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
     // [unord.map.modifiers], modifiers
     template<class... Args> pair<iterator, bool> emplace(Args&&... args);
     template<class H2, class P2>
       void merge(unordered_multimap<Key, T, H2, P2, Allocator>& source);
     template<class H2, class P2>
       void merge(unordered_multimap<Key, T, H2, P2, Allocator>&& source);
+    // observers
     hasher hash_function() const;
     key_equal key_eq() const;
+    // map operations
     iterator         find(const key_type& k);
     const_iterator   find(const key_type& k) const;
+    template<class K>
+      iterator       find(const K& k);
+    template<class K>
+      const_iterator find(const K& k) const;
+    template<class K>
     size_type        count(const key_type& k) const;
+    template<class K>
+      size_type      count(const K& k) const;
+    bool             contains(const key_type& k) const;
+    template<class K>
+      bool           contains(const K& k) const;
     pair<iterator, iterator>               equal_range(const key_type& k);
     pair<const_iterator, const_iterator>   equal_range(const key_type& k) const;
+    template<class K>
+      pair<iterator, iterator>             equal_range(const K& k);
+    template<class K>
+      pair<const_iterator, const_iterator> equal_range(const K& k) const;
     // [unord.map.elem], element access
     mapped_type& operator[](const key_type& k);
     mapped_type& operator[](key_type&& k);
     mapped_type& at(const key_type& k);
     const mapped_type& at(const key_type& k) const;
+    // bucket interface
     size_type bucket_count() const noexcept;
     size_type max_bucket_count() const noexcept;
     size_type bucket_size(size_type n) const;
     size_type bucket(const key_type& k) const;
     local_iterator begin(size_type n);
     local_iterator end(size_type n);
     const_local_iterator end(size_type n) const;
     const_local_iterator cbegin(size_type n) const;
     const_local_iterator cend(size_type n) const;
+    // hash policy
     float load_factor() const noexcept;
     float max_load_factor() const noexcept;
     void max_load_factor(float z);
     void rehash(size_type n);
     void reserve(size_type n);
   };
   template<class InputIterator,
+           class Hash = hash<iter-key-type<InputIterator>>,
+           class Pred = equal_to<iter-key-type<InputIterator>>,
+           class Allocator = allocator<iter-to-alloc-type<InputIterator>>>
     unordered_map(InputIterator, InputIterator, typename see below::size_type = see below,
                   Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+      -> unordered_map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>, Hash, Pred,
                        Allocator>;
   template<class Key, class T, class Hash = hash<Key>,
            class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>>
+    unordered_map(initializer_list<pair<Key, T>>,
                   typename see below::size_type = see below, Hash = Hash(),
                   Pred = Pred(), Allocator = Allocator())
       -> unordered_map<Key, T, Hash, Pred, Allocator>;
   template<class InputIterator, class Allocator>
     unordered_map(InputIterator, InputIterator, typename see below::size_type, Allocator)
+      -> unordered_map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+                       hash<iter-key-type<InputIterator>>,
+ equal_to<iter-key-type<InputIterator>>, Allocator>;
   template<class InputIterator, class Allocator>
     unordered_map(InputIterator, InputIterator, Allocator)
+      -> unordered_map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+                       hash<iter-key-type<InputIterator>>,
+ equal_to<iter-key-type<InputIterator>>, Allocator>;
   template<class InputIterator, class Hash, class Allocator>
     unordered_map(InputIterator, InputIterator, typename see below::size_type, Hash, Allocator)
+      -> unordered_map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>, Hash,
+                       equal_to<iter-key-type<InputIterator>>, Allocator>;
+  template<class Key, class T, class Allocator>
+    unordered_map(initializer_list<pair<Key, T>>, typename see below::size_type,
                   Allocator)
       -> unordered_map<Key, T, hash<Key>, equal_to<Key>, Allocator>;
+  template<class Key, class T, class Allocator>
+    unordered_map(initializer_list<pair<Key, T>>, Allocator)
       -> unordered_map<Key, T, hash<Key>, equal_to<Key>, Allocator>;
   template<class Key, class T, class Hash, class Allocator>
+    unordered_map(initializer_list<pair<Key, T>>, typename see below::size_type, Hash,
                   Allocator)
       -> unordered_map<Key, T, Hash, equal_to<Key>, Allocator>;
+ // swap
   template<class Key, class T, class Hash, class Pred, class Alloc>
     void swap(unordered_map<Key, T, Hash, Pred, Alloc>& x,
               unordered_map<Key, T, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
 }
 A `size_type` parameter type in an `unordered_map` deduction guide
 refers to the `size_type` member type of the type deduced by the
 deduction guide.
+#### Constructors <a id="unord.map.cnstr">[[unord.map.cnstr]]</a>
 ``` cpp
 unordered_map() : unordered_map(size_type(see below)) { }
 explicit unordered_map(size_type n,
                        const hasher& hf = hasher(),
 `l`) for the first form, or from the range \[`il.begin()`, `il.end()`)
 for the second form. `max_load_factor()` returns `1.0`.
 *Complexity:* Average case linear, worst case quadratic.
+#### Element access <a id="unord.map.elem">[[unord.map.elem]]</a>
 ``` cpp
 mapped_type& operator[](const key_type& k);
 ```
 whose key is equivalent to `k`.
 *Throws:* An exception object of type `out_of_range` if no such element
 is present.
+#### Modifiers <a id="unord.map.modifiers">[[unord.map.modifiers]]</a>
 ``` cpp
 template<class P>
   pair<iterator, bool> insert(P&& obj);
 ```
+*Constraints:* `is_constructible_v<value_type, P&&>` is `true`.
 *Effects:* Equivalent to: `return emplace(std::forward<P>(obj));`
 ``` cpp
 template<class P>
   iterator insert(const_iterator hint, P&& obj);
 ```
+*Constraints:* `is_constructible_v<value_type, P&&>` is `true`.
 *Effects:* Equivalent to:
 `return emplace_hint(hint, std::forward<P>(obj));`
 ``` cpp
 template<class... Args>
   pair<iterator, bool> try_emplace(const key_type& k, Args&&... args);
 template<class... Args>
   iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args);
 ```
+*Preconditions:* `value_type` is *Cpp17EmplaceConstructible* into
 `unordered_map` from `piecewise_construct`, `forward_as_tuple(k)`,
 `forward_as_tuple(std::forward<Args>(args)...)`.
 *Effects:* If the map already contains an element whose key is
 equivalent to `k`, there is no effect. Otherwise inserts an object of
   pair<iterator, bool> try_emplace(key_type&& k, Args&&... args);
 template<class... Args>
   iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args);
 ```
+*Preconditions:* `value_type` is *Cpp17EmplaceConstructible* into
 `unordered_map` from `piecewise_construct`,
 `forward_as_tuple(std::move(k))`,
 `forward_as_tuple(std::forward<Args>(args)...)`.
 *Effects:* If the map already contains an element whose key is
   pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj);
 template<class M>
   iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj);
 ```
+*Mandates:* `is_assignable_v<mapped_type&, M&&>` is `true`.
+*Preconditions:* `value_type` is *Cpp17EmplaceConstructible* into
+`unordered_map` from `k`, `std::forward<M>(obj)`.
 *Effects:* If the map already contains an element `e` whose key is
 equivalent to `k`, assigns `std::forward<M>(obj)` to `e.second`.
 Otherwise inserts an object of type `value_type` constructed with `k`,
 `std::forward<M>(obj)`.
   pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj);
 template<class M>
   iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj);
 ```
+*Mandates:* `is_assignable_v<mapped_type&, M&&>` is `true`.
+*Preconditions:* `value_type` is *Cpp17EmplaceConstructible* into
+`unordered_map` from `std::move(k)`, `std::forward<M>(obj)`.
 *Effects:* If the map already contains an element `e` whose key is
 equivalent to `k`, assigns `std::forward<M>(obj)` to `e.second`.
 Otherwise inserts an object of type `value_type` constructed with
 `std::move(k)`, `std::forward<M>(obj)`.
 pair is `true` if and only if the insertion took place. The returned
 iterator points to the map element whose key is equivalent to `k`.
 *Complexity:* The same as `emplace` and `emplace_hint`, respectively.
+#### Erasure <a id="unord.map.erasure">[[unord.map.erasure]]</a>
 ``` cpp
+template<class K, class T, class H, class P, class A, class Predicate>
+ typename unordered_map<K, T, H, P, A>::size_type
+    erase_if(unordered_map<K, T, H, P, A>& c, Predicate pred);
 ```
+*Effects:* Equivalent to:
+``` cpp
+auto original_size = c.size();
+for (auto i = c.begin(), last = c.end(); i != last; ) {
+  if (pred(*i)) {
+    i = c.erase(i);
+  } else {
+    ++i;
+  }
+}
+return original_size - c.size();
+```
 ### Class template `unordered_multimap` <a id="unord.multimap">[[unord.multimap]]</a>
+#### Overview <a id="unord.multimap.overview">[[unord.multimap.overview]]</a>
 An `unordered_multimap` is an unordered associative container that
 supports equivalent keys (an instance of `unordered_multimap` may
 contain multiple copies of each key value) and that associates values of
 another type `mapped_type` with the keys. The `unordered_multimap` class
 supports forward iterators.
+An `unordered_multimap` meets all of the requirements of a container, of
+an unordered associative container, and of an allocator-aware container
+([[container.alloc.req]]). It provides the operations described in the
+preceding requirements table for equivalent keys; that is, an
+`unordered_multimap` supports the `a_eq` operations in that table, not
+the `a_uniq` operations. For an `unordered_multimap<Key, T>` the
+`key type` is `Key`, the mapped type is `T`, and the value type is
+`pair<const Key, T>`.
+Subclause  [[unord.multimap]] only describes operations on
+`unordered_multimap` that are not described in one of the requirement
+tables, or for which there is additional semantic information.
 ``` cpp
 namespace std {
   template<class Key,
            class T,
            class Hash = hash<Key>,
            class Pred = equal_to<Key>,
            class Allocator = allocator<pair<const Key, T>>>
   class unordered_multimap {
   public:
+    // types
     using key_type             = Key;
     using mapped_type          = T;
     using value_type           = pair<const Key, T>;
     using hasher               = Hash;
     using key_equal            = Pred;
                is_nothrow_move_assignable_v<Hash> &&
                is_nothrow_move_assignable_v<Pred>);
     unordered_multimap& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
+    // iterators
     iterator       begin() noexcept;
     const_iterator begin() const noexcept;
     iterator       end() noexcept;
     const_iterator end() const noexcept;
     const_iterator cbegin() const noexcept;
     const_iterator cend() const noexcept;
+    // capacity
+ [[nodiscard]] bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
     // [unord.multimap.modifiers], modifiers
     template<class... Args> iterator emplace(Args&&... args);
     template<class H2, class P2>
       void merge(unordered_map<Key, T, H2, P2, Allocator>& source);
     template<class H2, class P2>
       void merge(unordered_map<Key, T, H2, P2, Allocator>&& source);
+    // observers
     hasher hash_function() const;
     key_equal key_eq() const;
+    // map operations
     iterator         find(const key_type& k);
     const_iterator   find(const key_type& k) const;
+    template<class K>
+      iterator       find(const K& k);
+    template<class K>
+      const_iterator find(const K& k) const;
     size_type        count(const key_type& k) const;
+    template<class K>
+      size_type      count(const K& k) const;
+    bool             contains(const key_type& k) const;
+    template<class K>
+      bool           contains(const K& k) const;
     pair<iterator, iterator>               equal_range(const key_type& k);
     pair<const_iterator, const_iterator>   equal_range(const key_type& k) const;
+    template<class K>
+      pair<iterator, iterator>             equal_range(const K& k);
+    template<class K>
+      pair<const_iterator, const_iterator> equal_range(const K& k) const;
+    // bucket interface
     size_type bucket_count() const noexcept;
     size_type max_bucket_count() const noexcept;
     size_type bucket_size(size_type n) const;
     size_type bucket(const key_type& k) const;
     local_iterator begin(size_type n);
     void rehash(size_type n);
     void reserve(size_type n);
   };
   template<class InputIterator,
+           class Hash = hash<iter-key-type<InputIterator>>,
+           class Pred = equal_to<iter-key-type<InputIterator>>,
+           class Allocator = allocator<iter-to-alloc-type<InputIterator>>>
     unordered_multimap(InputIterator, InputIterator,
                        typename see below::size_type = see below,
                        Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+      -> unordered_multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+ Hash, Pred, Allocator>;
   template<class Key, class T, class Hash = hash<Key>,
            class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>>
+    unordered_multimap(initializer_list<pair<Key, T>>,
                        typename see below::size_type = see below,
                        Hash = Hash(), Pred = Pred(), Allocator = Allocator())
       -> unordered_multimap<Key, T, Hash, Pred, Allocator>;
   template<class InputIterator, class Allocator>
     unordered_multimap(InputIterator, InputIterator, typename see below::size_type, Allocator)
+      -> unordered_multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+                            hash<iter-key-type<InputIterator>>,
+                            equal_to<iter-key-type<InputIterator>>, Allocator>;
   template<class InputIterator, class Allocator>
     unordered_multimap(InputIterator, InputIterator, Allocator)
+      -> unordered_multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+                            hash<iter-key-type<InputIterator>>,
+                            equal_to<iter-key-type<InputIterator>>, Allocator>;
   template<class InputIterator, class Hash, class Allocator>
     unordered_multimap(InputIterator, InputIterator, typename see below::size_type, Hash,
                        Allocator)
+      -> unordered_multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>, Hash,
+                            equal_to<iter-key-type<InputIterator>>, Allocator>;
+  template<class Key, class T, class Allocator>
+    unordered_multimap(initializer_list<pair<Key, T>>, typename see below::size_type,
                        Allocator)
       -> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>;
+  template<class Key, class T, class Allocator>
+    unordered_multimap(initializer_list<pair<Key, T>>, Allocator)
       -> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>;
   template<class Key, class T, class Hash, class Allocator>
+    unordered_multimap(initializer_list<pair<Key, T>>, typename see below::size_type,
                        Hash, Allocator)
       -> unordered_multimap<Key, T, Hash, equal_to<Key>, Allocator>;
+ // swap
   template<class Key, class T, class Hash, class Pred, class Alloc>
     void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x,
               unordered_multimap<Key, T, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
 }
 A `size_type` parameter type in an `unordered_multimap` deduction guide
 refers to the `size_type` member type of the type deduced by the
 deduction guide.
+#### Constructors <a id="unord.multimap.cnstr">[[unord.multimap.cnstr]]</a>
 ``` cpp
 unordered_multimap() : unordered_multimap(size_type(see below)) { }
 explicit unordered_multimap(size_type n,
                             const hasher& hf = hasher(),
 `l`) for the first form, or from the range \[`il.begin()`, `il.end()`)
 for the second form. `max_load_factor()` returns `1.0`.
 *Complexity:* Average case linear, worst case quadratic.
+#### Modifiers <a id="unord.multimap.modifiers">[[unord.multimap.modifiers]]</a>
 ``` cpp
 template<class P>
   iterator insert(P&& obj);
 ```
+*Constraints:* `is_constructible_v<value_type, P&&>` is `true`.
 *Effects:* Equivalent to: `return emplace(std::forward<P>(obj));`
 ``` cpp
 template<class P>
   iterator insert(const_iterator hint, P&& obj);
 ```
+*Constraints:* `is_constructible_v<value_type, P&&>` is `true`.
 *Effects:* Equivalent to:
 `return emplace_hint(hint, std::forward<P>(obj));`
+#### Erasure <a id="unord.multimap.erasure">[[unord.multimap.erasure]]</a>
 ``` cpp
+template<class K, class T, class H, class P, class A, class Predicate>
+ typename unordered_multimap<K, T, H, P, A>::size_type
+    erase_if(unordered_multimap<K, T, H, P, A>& c, Predicate pred);
 ```
+*Effects:* Equivalent to:
+``` cpp
+auto original_size = c.size();
+for (auto i = c.begin(), last = c.end(); i != last; ) {
+  if (pred(*i)) {
+    i = c.erase(i);
+  } else {
+    ++i;
+  }
+}
+return original_size - c.size();
+```
 ### Class template `unordered_set` <a id="unord.set">[[unord.set]]</a>
+#### Overview <a id="unord.set.overview">[[unord.set.overview]]</a>
 An `unordered_set` is an unordered associative container that supports
 unique keys (an `unordered_set` contains at most one of each key value)
 and in which the elements’ keys are the elements themselves. The
 `unordered_set` class supports forward iterators.
+An `unordered_set` meets all of the requirements of a container, of an
+unordered associative container, and of an allocator-aware container (
+[[container.alloc.req]]). It provides the operations described in the
+preceding requirements table for unique keys; that is, an
+`unordered_set` supports the `a_uniq` operations in that table, not the
+`a_eq` operations. For an `unordered_set<Key>` the `key type` and the
+value type are both `Key`. The `iterator` and `const_iterator` types are
+both constant iterator types. It is unspecified whether they are the
 same type.
+Subclause  [[unord.set]] only describes operations on `unordered_set`
+that are not described in one of the requirement tables, or for which
+there is additional semantic information.
 ``` cpp
 namespace std {
   template<class Key,
            class Hash = hash<Key>,
            class Pred = equal_to<Key>,
            class Allocator = allocator<Key>>
   class unordered_set {
   public:
+    // types
     using key_type             = Key;
     using value_type           = Key;
     using hasher               = Hash;
     using key_equal            = Pred;
     using allocator_type       = Allocator;
     using iterator             = implementation-defined  // type of unordered_set::iterator; // see [container.requirements]
     using const_iterator       = implementation-defined  // type of unordered_set::const_iterator; // see [container.requirements]
     using local_iterator       = implementation-defined  // type of unordered_set::local_iterator; // see [container.requirements]
     using const_local_iterator = implementation-defined  // type of unordered_set::const_local_iterator; // see [container.requirements]
     using node_type            = unspecified;
+    using insert_return_type   = insert-return-type<iterator, node_type>;
     // [unord.set.cnstr], construct/copy/destroy
     unordered_set();
     explicit unordered_set(size_type n,
                            const hasher& hf = hasher(),
                is_nothrow_move_assignable_v<Hash> &&
                is_nothrow_move_assignable_v<Pred>);
     unordered_set& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
+    // iterators
     iterator       begin() noexcept;
     const_iterator begin() const noexcept;
     iterator       end() noexcept;
     const_iterator end() const noexcept;
     const_iterator cbegin() const noexcept;
     const_iterator cend() const noexcept;
+    // capacity
+ [[nodiscard]] bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
+    // modifiers
     template<class... Args> pair<iterator, bool> emplace(Args&&... args);
     template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
     pair<iterator, bool> insert(const value_type& obj);
     pair<iterator, bool> insert(value_type&& obj);
     iterator insert(const_iterator hint, const value_type& obj);
     template<class H2, class P2>
       void merge(unordered_multiset<Key, H2, P2, Allocator>& source);
     template<class H2, class P2>
       void merge(unordered_multiset<Key, H2, P2, Allocator>&& source);
+    // observers
     hasher hash_function() const;
     key_equal key_eq() const;
+    // set operations
     iterator         find(const key_type& k);
     const_iterator   find(const key_type& k) const;
+    template<class K>
+      iterator       find(const K& k);
+    template<class K>
+      const_iterator find(const K& k) const;
     size_type        count(const key_type& k) const;
+    template<class K>
+      size_type      count(const K& k) const;
+    bool             contains(const key_type& k) const;
+    template<class K>
+      bool           contains(const K& k) const;
     pair<iterator, iterator>               equal_range(const key_type& k);
     pair<const_iterator, const_iterator>   equal_range(const key_type& k) const;
+    template<class K>
+      pair<iterator, iterator>             equal_range(const K& k);
+    template<class K>
+      pair<const_iterator, const_iterator> equal_range(const K& k) const;
+    // bucket interface
     size_type bucket_count() const noexcept;
     size_type max_bucket_count() const noexcept;
     size_type bucket_size(size_type n) const;
     size_type bucket(const key_type& k) const;
     local_iterator begin(size_type n);
     local_iterator end(size_type n);
     const_local_iterator end(size_type n) const;
     const_local_iterator cbegin(size_type n) const;
     const_local_iterator cend(size_type n) const;
+    // hash policy
     float load_factor() const noexcept;
     float max_load_factor() const noexcept;
     void max_load_factor(float z);
     void rehash(size_type n);
     void reserve(size_type n);
   };
   template<class InputIterator,
+           class Hash = hash<iter-value-type<InputIterator>>,
+           class Pred = equal_to<iter-value-type<InputIterator>>,
+           class Allocator = allocator<iter-value-type<InputIterator>>>
     unordered_set(InputIterator, InputIterator, typename see below::size_type = see below,
                   Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+      -> unordered_set<iter-value-type<InputIterator>,
                        Hash, Pred, Allocator>;
   template<class T, class Hash = hash<T>,
            class Pred = equal_to<T>, class Allocator = allocator<T>>
     unordered_set(initializer_list<T>, typename see below::size_type = see below,
                   Hash = Hash(), Pred = Pred(), Allocator = Allocator())
       -> unordered_set<T, Hash, Pred, Allocator>;
   template<class InputIterator, class Allocator>
     unordered_set(InputIterator, InputIterator, typename see below::size_type, Allocator)
+      -> unordered_set<iter-value-type<InputIterator>,
+                       hash<iter-value-type<InputIterator>>,
+                       equal_to<iter-value-type<InputIterator>>,
                        Allocator>;
   template<class InputIterator, class Hash, class Allocator>
     unordered_set(InputIterator, InputIterator, typename see below::size_type,
                   Hash, Allocator)
+      -> unordered_set<iter-value-type<InputIterator>, Hash,
+                       equal_to<iter-value-type<InputIterator>>,
                        Allocator>;
   template<class T, class Allocator>
     unordered_set(initializer_list<T>, typename see below::size_type, Allocator)
       -> unordered_set<T, hash<T>, equal_to<T>, Allocator>;
   template<class T, class Hash, class Allocator>
     unordered_set(initializer_list<T>, typename see below::size_type, Hash, Allocator)
       -> unordered_set<T, Hash, equal_to<T>, Allocator>;
+ // swap
   template<class Key, class Hash, class Pred, class Alloc>
     void swap(unordered_set<Key, Hash, Pred, Alloc>& x,
               unordered_set<Key, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
 A `size_type` parameter type in an `unordered_set` deduction guide
+refers to the `size_type` member type of the type deduced by the
+deduction guide.
+#### Constructors <a id="unord.set.cnstr">[[unord.set.cnstr]]</a>
 ``` cpp
 unordered_set() : unordered_set(size_type(see below)) { }
 explicit unordered_set(size_type n,
                        const hasher& hf = hasher(),
 `l`) for the first form, or from the range \[`il.begin()`, `il.end()`)
 for the second form. `max_load_factor()` returns `1.0`.
 *Complexity:* Average case linear, worst case quadratic.
+#### Erasure <a id="unord.set.erasure">[[unord.set.erasure]]</a>
 ``` cpp
+template<class K, class H, class P, class A, class Predicate>
+ typename unordered_set<K, H, P, A>::size_type
+    erase_if(unordered_set<K, H, P, A>& c, Predicate pred);
 ```
+*Effects:* Equivalent to:
+``` cpp
+auto original_size = c.size();
+for (auto i = c.begin(), last = c.end(); i != last; ) {
+  if (pred(*i)) {
+    i = c.erase(i);
+  } else {
+    ++i;
+  }
+}
+return original_size - c.size();
+```
 ### Class template `unordered_multiset` <a id="unord.multiset">[[unord.multiset]]</a>
+#### Overview <a id="unord.multiset.overview">[[unord.multiset.overview]]</a>
 An `unordered_multiset` is an unordered associative container that
 supports equivalent keys (an instance of `unordered_multiset` may
 contain multiple copies of the same key value) and in which each
 element’s key is the element itself. The `unordered_multiset` class
 supports forward iterators.
+An `unordered_multiset` meets all of the requirements of a container, of
+an unordered associative container, and of an allocator-aware container
+([[container.alloc.req]]). It provides the operations described in the
+preceding requirements table for equivalent keys; that is, an
+`unordered_multiset` supports the `a_eq` operations in that table, not
+the `a_uniq` operations. For an `unordered_multiset<Key>` the `key type`
+and the value type are both `Key`. The `iterator` and `const_iterator`
+types are both constant iterator types. It is unspecified whether they
+are the same type.
+Subclause  [[unord.multiset]] only describes operations on
+`unordered_multiset` that are not described in one of the requirement
+tables, or for which there is additional semantic information.
 ``` cpp
 namespace std {
   template<class Key,
            class Hash = hash<Key>,
            class Pred = equal_to<Key>,
            class Allocator = allocator<Key>>
   class unordered_multiset {
   public:
+    // types
     using key_type             = Key;
     using value_type           = Key;
     using hasher               = Hash;
     using key_equal            = Pred;
     using allocator_type       = Allocator;
                is_nothrow_move_assignable_v<Hash> &&
                is_nothrow_move_assignable_v<Pred>);
     unordered_multiset& operator=(initializer_list<value_type>);
     allocator_type get_allocator() const noexcept;
+    // iterators
     iterator       begin() noexcept;
     const_iterator begin() const noexcept;
     iterator       end() noexcept;
     const_iterator end() const noexcept;
     const_iterator cbegin() const noexcept;
     const_iterator cend() const noexcept;
+    // capacity
+ [[nodiscard]] bool empty() const noexcept;
     size_type size() const noexcept;
     size_type max_size() const noexcept;
+    // modifiers
     template<class... Args> iterator emplace(Args&&... args);
     template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
     iterator insert(const value_type& obj);
     iterator insert(value_type&& obj);
     iterator insert(const_iterator hint, const value_type& obj);
     template<class H2, class P2>
       void merge(unordered_set<Key, H2, P2, Allocator>& source);
     template<class H2, class P2>
       void merge(unordered_set<Key, H2, P2, Allocator>&& source);
+    // observers
     hasher hash_function() const;
     key_equal key_eq() const;
+    // set operations
     iterator         find(const key_type& k);
     const_iterator   find(const key_type& k) const;
+    template<class K>
+      iterator       find(const K& k);
+    template<class K>
+      const_iterator find(const K& k) const;
     size_type        count(const key_type& k) const;
+    template<class K>
+      size_type      count(const K& k) const;
+    bool             contains(const key_type& k) const;
+    template<class K>
+      bool           contains(const K& k) const;
     pair<iterator, iterator>               equal_range(const key_type& k);
     pair<const_iterator, const_iterator>   equal_range(const key_type& k) const;
+    template<class K>
+      pair<iterator, iterator>             equal_range(const K& k);
+    template<class K>
+      pair<const_iterator, const_iterator> equal_range(const K& k) const;
+    // bucket interface
     size_type bucket_count() const noexcept;
     size_type max_bucket_count() const noexcept;
     size_type bucket_size(size_type n) const;
     size_type bucket(const key_type& k) const;
     local_iterator begin(size_type n);
     local_iterator end(size_type n);
     const_local_iterator end(size_type n) const;
     const_local_iterator cbegin(size_type n) const;
     const_local_iterator cend(size_type n) const;
+    // hash policy
     float load_factor() const noexcept;
     float max_load_factor() const noexcept;
     void max_load_factor(float z);
     void rehash(size_type n);
     void reserve(size_type n);
   };
   template<class InputIterator,
+           class Hash = hash<iter-value-type<InputIterator>>,
+           class Pred = equal_to<iter-value-type<InputIterator>>,
+           class Allocator = allocator<iter-value-type<InputIterator>>>
     unordered_multiset(InputIterator, InputIterator, see below::size_type = see below,
                        Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+      -> unordered_multiset<iter-value-type<InputIterator>,
                             Hash, Pred, Allocator>;
   template<class T, class Hash = hash<T>,
            class Pred = equal_to<T>, class Allocator = allocator<T>>
     unordered_multiset(initializer_list<T>, typename see below::size_type = see below,
                        Hash = Hash(), Pred = Pred(), Allocator = Allocator())
       -> unordered_multiset<T, Hash, Pred, Allocator>;
   template<class InputIterator, class Allocator>
     unordered_multiset(InputIterator, InputIterator, typename see below::size_type, Allocator)
+      -> unordered_multiset<iter-value-type<InputIterator>,
+                            hash<iter-value-type<InputIterator>>,
+                            equal_to<iter-value-type<InputIterator>>,
                             Allocator>;
   template<class InputIterator, class Hash, class Allocator>
     unordered_multiset(InputIterator, InputIterator, typename see below::size_type,
                        Hash, Allocator)
+      -> unordered_multiset<iter-value-type<InputIterator>, Hash,
+                            equal_to<iter-value-type<InputIterator>>,
                             Allocator>;
   template<class T, class Allocator>
     unordered_multiset(initializer_list<T>, typename see below::size_type, Allocator)
       -> unordered_multiset<T, hash<T>, equal_to<T>, Allocator>;
   template<class T, class Hash, class Allocator>
     unordered_multiset(initializer_list<T>, typename see below::size_type, Hash, Allocator)
       -> unordered_multiset<T, Hash, equal_to<T>, Allocator>;
+ // swap
   template<class Key, class Hash, class Pred, class Alloc>
     void swap(unordered_multiset<Key, Hash, Pred, Alloc>& x,
               unordered_multiset<Key, Hash, Pred, Alloc>& y)
       noexcept(noexcept(x.swap(y)));
 }
 ```
 A `size_type` parameter type in an `unordered_multiset` deduction guide
+refers to the `size_type` member type of the type deduced by the
+deduction guide.
+#### Constructors <a id="unord.multiset.cnstr">[[unord.multiset.cnstr]]</a>
 ``` cpp
 unordered_multiset() : unordered_multiset(size_type(see below)) { }
 explicit unordered_multiset(size_type n,
                             const hasher& hf = hasher(),
 `l`) for the first form, or from the range \[`il.begin()`, `il.end()`)
 for the second form. `max_load_factor()` returns `1.0`.
 *Complexity:* Average case linear, worst case quadratic.
+#### Erasure <a id="unord.multiset.erasure">[[unord.multiset.erasure]]</a>
 ``` cpp
+template<class K, class H, class P, class A, class Predicate>
+ typename unordered_multiset<K, H, P, A>::size_type
+    erase_if(unordered_multiset<K, H, P, A>& c, Predicate pred);
 ```
+*Effects:* Equivalent to:
+``` cpp
+auto original_size = c.size();
+for (auto i = c.begin(), last = c.end(); i != last; ) {
+  if (pred(*i)) {
+    i = c.erase(i);
+  } else {
+    ++i;
+  }
+}
+return original_size - c.size();
+```
 ## Container adaptors <a id="container.adaptors">[[container.adaptors]]</a>
 ### In general <a id="container.adaptors.general">[[container.adaptors.general]]</a>
   `uses_allocator_v<Container, Allocator>` is `false`.
 ### Header `<queue>` synopsis <a id="queue.syn">[[queue.syn]]</a>
 ``` cpp
+#include <compare>              // see [compare.syn]
+#include <initializer_list>     // see [initializer.list.syn]
 namespace std {
   template<class T, class Container = deque<T>> class queue;
+  template<class T, class Container>
+    bool operator==(const queue<T, Container>& x, const queue<T, Container>& y);
+  template<class T, class Container>
+    bool operator!=(const queue<T, Container>& x, const queue<T, Container>& y);
+  template<class T, class Container>
+    bool operator< (const queue<T, Container>& x, const queue<T, Container>& y);
+  template<class T, class Container>
+    bool operator> (const queue<T, Container>& x, const queue<T, Container>& y);
+  template<class T, class Container>
+    bool operator<=(const queue<T, Container>& x, const queue<T, Container>& y);
+  template<class T, class Container>
+    bool operator>=(const queue<T, Container>& x, const queue<T, Container>& y);
+  template<class T, three_way_comparable Container>
+    compare_three_way_result_t<Container>
+      operator<=>(const queue<T, Container>& x, const queue<T, Container>& y);
+  template<class T, class Container>
+    void swap(queue<T, Container>& x, queue<T, Container>& y) noexcept(noexcept(x.swap(y)));
+  template<class T, class Container, class Alloc>
+    struct uses_allocator<queue<T, Container>, Alloc>;
   template<class T, class Container = vector<T>,
            class Compare = less<typename Container::value_type>>
     class priority_queue;
   template<class T, class Container, class Compare>
     void swap(priority_queue<T, Container, Compare>& x,
               priority_queue<T, Container, Compare>& y) noexcept(noexcept(x.swap(y)));
+  template<class T, class Container, class Compare, class Alloc>
+    struct uses_allocator<priority_queue<T, Container, Compare>, Alloc>;
 }
 ```
 ### Header `<stack>` synopsis <a id="stack.syn">[[stack.syn]]</a>
 ``` cpp
+#include <compare>              // see [compare.syn]
+#include <initializer_list>     // see [initializer.list.syn]
 namespace std {
   template<class T, class Container = deque<T>> class stack;
   template<class T, class Container>
     bool operator==(const stack<T, Container>& x, const stack<T, Container>& y);
   template<class T, class Container>
     bool operator!=(const stack<T, Container>& x, const stack<T, Container>& y);
+  template<class T, class Container>
+    bool operator< (const stack<T, Container>& x, const stack<T, Container>& y);
   template<class T, class Container>
     bool operator> (const stack<T, Container>& x, const stack<T, Container>& y);
   template<class T, class Container>
     bool operator<=(const stack<T, Container>& x, const stack<T, Container>& y);
+  template<class T, class Container>
+    bool operator>=(const stack<T, Container>& x, const stack<T, Container>& y);
+  template<class T, three_way_comparable Container>
+    compare_three_way_result_t<Container>
+      operator<=>(const stack<T, Container>& x, const stack<T, Container>& y);
   template<class T, class Container>
     void swap(stack<T, Container>& x, stack<T, Container>& y) noexcept(noexcept(x.swap(y)));
+  template<class T, class Container, class Alloc>
+    struct uses_allocator<stack<T, Container>, Alloc>;
 }
 ```
 ### Class template `queue` <a id="queue">[[queue]]</a>
+#### Definition <a id="queue.defn">[[queue.defn]]</a>
 Any sequence container supporting operations `front()`, `back()`,
 `push_back()` and `pop_front()` can be used to instantiate `queue`. In
+particular, `list` [[list]] and `deque` [[deque]] can be used.
 ``` cpp
 namespace std {
   template<class T, class Container = deque<T>>
   class queue {
   protected:
     Container c;
   public:
+    queue() : queue(Container()) {}
     explicit queue(const Container&);
+    explicit queue(Container&&);
     template<class Alloc> explicit queue(const Alloc&);
     template<class Alloc> queue(const Container&, const Alloc&);
     template<class Alloc> queue(Container&&, const Alloc&);
     template<class Alloc> queue(const queue&, const Alloc&);
     template<class Alloc> queue(queue&&, const Alloc&);
+ [[nodiscard]] bool empty() const { return c.empty(); }
     size_type         size()  const     { return c.size(); }
     reference         front()           { return c.front(); }
     const_reference   front() const     { return c.front(); }
     reference         back()            { return c.back(); }
     const_reference   back() const      { return c.back(); }
     void push(const value_type& x)      { c.push_back(x); }
     void push(value_type&& x)           { c.push_back(std::move(x)); }
     template<class... Args>
+ decltype(auto) emplace(Args&&... args)
+        { return c.emplace_back(std::forward<Args>(args)...); }
     void pop()                          { c.pop_front(); }
     void swap(queue& q) noexcept(is_nothrow_swappable_v<Container>)
       { using std::swap; swap(c, q.c); }
   };
     queue(Container) -> queue<typename Container::value_type, Container>;
   template<class Container, class Allocator>
     queue(Container, Allocator) -> queue<typename Container::value_type, Container>;
   template<class T, class Container>
     void swap(queue<T, Container>& x, queue<T, Container>& y) noexcept(noexcept(x.swap(y)));
   template<class T, class Container, class Alloc>
     struct uses_allocator<queue<T, Container>, Alloc>
       : uses_allocator<Container, Alloc>::type { };
 }
 ```
+#### Constructors <a id="queue.cons">[[queue.cons]]</a>
 ``` cpp
 explicit queue(const Container& cont);
 ```
+*Effects:* Initializes `c` with `cont`.
 ``` cpp
+explicit queue(Container&& cont);
 ```
+*Effects:* Initializes `c` with `std::move(cont)`.
+#### Constructors with allocators <a id="queue.cons.alloc">[[queue.cons.alloc]]</a>
 If `uses_allocator_v<container_type, Alloc>` is `false` the constructors
 in this subclause shall not participate in overload resolution.
 ``` cpp
 template<class Alloc> explicit queue(const Alloc& a);
 ```
+*Effects:* Initializes `c` with `a`.
 ``` cpp
 template<class Alloc> queue(const container_type& cont, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `cont` as the first argument and `a` as
 the second argument.
 ``` cpp
 template<class Alloc> queue(container_type&& cont, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `std::move(cont)` as the first argument
 and `a` as the second argument.
 ``` cpp
 template<class Alloc> queue(const queue& q, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `q.c` as the first argument and `a` as
 the second argument.
 ``` cpp
 template<class Alloc> queue(queue&& q, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `std::move(q.c)` as the first argument
 and `a` as the second argument.
+#### Operators <a id="queue.ops">[[queue.ops]]</a>
 ``` cpp
 template<class T, class Container>
   bool operator==(const queue<T, Container>& x, const queue<T, Container>& y);
 ```
   bool operator< (const queue<T, Container>& x, const queue<T, Container>& y);
 ```
 *Returns:* `x.c < y.c`.
 ``` cpp
 template<class T, class Container>
   bool operator> (const queue<T, Container>& x, const queue<T, Container>& y);
 ```
 *Returns:* `x.c > y.c`.
+``` cpp
+template<class T, class Container>
+  bool operator<=(const queue<T, Container>& x, const queue<T, Container>& y);
+```
+*Returns:* `x.c <= y.c`.
 ``` cpp
 template<class T, class Container>
     bool operator>=(const queue<T, Container>& x,
                     const queue<T, Container>& y);
 ```
 *Returns:* `x.c >= y.c`.
+``` cpp
+template<class T, three_way_comparable Container>
+  compare_three_way_result_t<Container>
+    operator<=>(const queue<T, Container>& x, const queue<T, Container>& y);
+```
+*Returns:* `x.c <=> y.c`.
+#### Specialized algorithms <a id="queue.special">[[queue.special]]</a>
 ``` cpp
 template<class T, class Container>
   void swap(queue<T, Container>& x, queue<T, Container>& y) noexcept(noexcept(x.swap(y)));
 ```
+*Constraints:* `is_swappable_v<Container>` is `true`.
 *Effects:* As if by `x.swap(y)`.
 ### Class template `priority_queue` <a id="priority.queue">[[priority.queue]]</a>
+#### Overview <a id="priqueue.overview">[[priqueue.overview]]</a>
 Any sequence container with random access iterator and supporting
 operations `front()`, `push_back()` and `pop_back()` can be used to
+instantiate `priority_queue`. In particular, `vector` [[vector]] and
+`deque` [[deque]] can be used. Instantiating `priority_queue` also
 involves supplying a function or function object for making priority
 comparisons; the library assumes that the function or function object
+defines a strict weak ordering [[alg.sorting]].
 ``` cpp
 namespace std {
   template<class T, class Container = vector<T>,
            class Compare = less<typename Container::value_type>>
   protected:
     Container c;
     Compare comp;
   public:
+    priority_queue() : priority_queue(Compare()) {}
+    explicit priority_queue(const Compare& x) : priority_queue(x, Container()) {}
     priority_queue(const Compare& x, const Container&);
+    priority_queue(const Compare& x, Container&&);
     template<class InputIterator>
+      priority_queue(InputIterator first, InputIterator last, const Compare& x,
+ const Container&);
     template<class InputIterator>
       priority_queue(InputIterator first, InputIterator last,
                      const Compare& x = Compare(), Container&& = Container());
     template<class Alloc> explicit priority_queue(const Alloc&);
     template<class Alloc> priority_queue(const Compare&, const Alloc&);
     template<class Alloc> priority_queue(const Compare&, const Container&, const Alloc&);
     template<class Alloc> priority_queue(const Compare&, Container&&, const Alloc&);
     template<class Alloc> priority_queue(const priority_queue&, const Alloc&);
     template<class Alloc> priority_queue(priority_queue&&, const Alloc&);
+ [[nodiscard]] bool empty() const { return c.empty(); }
     size_type size()  const          { return c.size(); }
     const_reference   top() const    { return c.front(); }
     void push(const value_type& x);
     void push(value_type&& x);
     template<class... Args> void emplace(Args&&... args);
     struct uses_allocator<priority_queue<T, Container, Compare>, Alloc>
       : uses_allocator<Container, Alloc>::type { };
 }
 ```
+#### Constructors <a id="priqueue.cons">[[priqueue.cons]]</a>
 ``` cpp
 priority_queue(const Compare& x, const Container& y);
+priority_queue(const Compare& x, Container&& y);
 ```
+*Preconditions:* `x` defines a strict weak ordering [[alg.sorting]].
 *Effects:* Initializes `comp` with `x` and `c` with `y` (copy
 constructing or move constructing as appropriate); calls
 `make_heap(c.begin(), c.end(), comp)`.
 ``` cpp
 template<class InputIterator>
+  priority_queue(InputIterator first, InputIterator last, const Compare& x, const Container& y);
 template<class InputIterator>
+  priority_queue(InputIterator first, InputIterator last, const Compare& x = Compare(),
                  Container&& y = Container());
 ```
+*Preconditions:* `x` defines a strict weak ordering [[alg.sorting]].
 *Effects:* Initializes `comp` with `x` and `c` with `y` (copy
 constructing or move constructing as appropriate); calls
 `c.insert(c.end(), first, last)`; and finally calls
 `make_heap(c.begin(), c.end(), comp)`.
+#### Constructors with allocators <a id="priqueue.cons.alloc">[[priqueue.cons.alloc]]</a>
 If `uses_allocator_v<container_type, Alloc>` is `false` the constructors
 in this subclause shall not participate in overload resolution.
 ``` cpp
 template<class Alloc> explicit priority_queue(const Alloc& a);
 ```
+*Effects:* Initializes `c` with `a` and value-initializes `comp`.
 ``` cpp
 template<class Alloc> priority_queue(const Compare& compare, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `a` and initializes `comp` with
 `compare`.
 ``` cpp
 template<class Alloc>
   priority_queue(const Compare& compare, const Container& cont, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `cont` as the first argument and `a` as
 the second argument, and initializes `comp` with `compare`; calls
 `make_heap(c.begin(), c.end(), comp)`.
 ``` cpp
 template<class Alloc>
   priority_queue(const Compare& compare, Container&& cont, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `std::move(cont)` as the first argument
 and `a` as the second argument, and initializes `comp` with `compare`;
 calls `make_heap(c.begin(), c.end(), comp)`.
 ``` cpp
 template<class Alloc> priority_queue(const priority_queue& q, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `q.c` as the first argument and `a` as
 the second argument, and initializes `comp` with `q.comp`.
 ``` cpp
 template<class Alloc> priority_queue(priority_queue&& q, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `std::move(q.c)` as the first argument
 and `a` as the second argument, and initializes `comp` with
 `std::move(q.comp)`.
+#### Members <a id="priqueue.members">[[priqueue.members]]</a>
 ``` cpp
 void push(const value_type& x);
 ```
 c.push_back(std::move(x));
 push_heap(c.begin(), c.end(), comp);
 ```
 ``` cpp
+template<class... Args> void emplace(Args&&... args);
 ```
 *Effects:* As if by:
 ``` cpp
 ``` cpp
 pop_heap(c.begin(), c.end(), comp);
 c.pop_back();
 ```
+#### Specialized algorithms <a id="priqueue.special">[[priqueue.special]]</a>
 ``` cpp
 template<class T, class Container, class Compare>
   void swap(priority_queue<T, Container, Compare>& x,
             priority_queue<T, Container, Compare>& y) noexcept(noexcept(x.swap(y)));
 ```
+*Constraints:* `is_swappable_v<Container>` is `true` and
 `is_swappable_v<Compare>` is `true`.
 *Effects:* As if by `x.swap(y)`.
 ### Class template `stack` <a id="stack">[[stack]]</a>
 Any sequence container supporting operations `back()`, `push_back()` and
+`pop_back()` can be used to instantiate `stack`. In particular, `vector`
+[[vector]], `list` [[list]] and `deque` [[deque]] can be used.
+#### Definition <a id="stack.defn">[[stack.defn]]</a>
 ``` cpp
 namespace std {
   template<class T, class Container = deque<T>>
   class stack {
   protected:
     Container c;
   public:
+    stack() : stack(Container()) {}
     explicit stack(const Container&);
+    explicit stack(Container&&);
     template<class Alloc> explicit stack(const Alloc&);
     template<class Alloc> stack(const Container&, const Alloc&);
     template<class Alloc> stack(Container&&, const Alloc&);
     template<class Alloc> stack(const stack&, const Alloc&);
     template<class Alloc> stack(stack&&, const Alloc&);
+ [[nodiscard]] bool empty() const { return c.empty(); }
     size_type size()  const             { return c.size(); }
     reference         top()             { return c.back(); }
     const_reference   top() const       { return c.back(); }
     void push(const value_type& x)      { c.push_back(x); }
     void push(value_type&& x)           { c.push_back(std::move(x)); }
     template<class... Args>
+ decltype(auto) emplace(Args&&... args)
+        { return c.emplace_back(std::forward<Args>(args)...); }
     void pop()                          { c.pop_back(); }
     void swap(stack& s) noexcept(is_nothrow_swappable_v<Container>)
       { using std::swap; swap(c, s.c); }
   };
     stack(Container) -> stack<typename Container::value_type, Container>;
   template<class Container, class Allocator>
     stack(Container, Allocator) -> stack<typename Container::value_type, Container>;
   template<class T, class Container, class Alloc>
     struct uses_allocator<stack<T, Container>, Alloc>
       : uses_allocator<Container, Alloc>::type { };
 }
 ```
+#### Constructors <a id="stack.cons">[[stack.cons]]</a>
 ``` cpp
 explicit stack(const Container& cont);
 ```
 *Effects:* Initializes `c` with `cont`.
 ``` cpp
+explicit stack(Container&& cont);
 ```
 *Effects:* Initializes `c` with `std::move(cont)`.
+#### Constructors with allocators <a id="stack.cons.alloc">[[stack.cons.alloc]]</a>
 If `uses_allocator_v<container_type, Alloc>` is `false` the constructors
 in this subclause shall not participate in overload resolution.
 ``` cpp
 template<class Alloc> explicit stack(const Alloc& a);
 ```
+*Effects:* Initializes `c` with `a`.
 ``` cpp
 template<class Alloc> stack(const container_type& cont, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `cont` as the first argument and `a` as
 the second argument.
 ``` cpp
 template<class Alloc> stack(container_type&& cont, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `std::move(cont)` as the first argument
 and `a` as the second argument.
 ``` cpp
 template<class Alloc> stack(const stack& s, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `s.c` as the first argument and `a` as
 the second argument.
 ``` cpp
 template<class Alloc> stack(stack&& s, const Alloc& a);
 ```
+*Effects:* Initializes `c` with `std::move(s.c)` as the first argument
 and `a` as the second argument.
+#### Operators <a id="stack.ops">[[stack.ops]]</a>
 ``` cpp
 template<class T, class Container>
   bool operator==(const stack<T, Container>& x, const stack<T, Container>& y);
 ```
   bool operator< (const stack<T, Container>& x, const stack<T, Container>& y);
 ```
 *Returns:* `x.c < y.c`.
 ``` cpp
 template<class T, class Container>
   bool operator> (const stack<T, Container>& x, const stack<T, Container>& y);
 ```
 *Returns:* `x.c > y.c`.
+``` cpp
+template<class T, class Container>
+  bool operator<=(const stack<T, Container>& x, const stack<T, Container>& y);
+```
+*Returns:* `x.c <= y.c`.
 ``` cpp
 template<class T, class Container>
     bool operator>=(const stack<T, Container>& x, const stack<T, Container>& y);
 ```
 *Returns:* `x.c >= y.c`.
+``` cpp
+template<class T, three_way_comparable Container>
+  compare_three_way_result_t<Container>
+    operator<=>(const stack<T, Container>& x, const stack<T, Container>& y);
+```
+*Returns:* `x.c <=> y.c`.
+#### Specialized algorithms <a id="stack.special">[[stack.special]]</a>
 ``` cpp
 template<class T, class Container>
   void swap(stack<T, Container>& x, stack<T, Container>& y) noexcept(noexcept(x.swap(y)));
 ```
+*Constraints:* `is_swappable_v<Container>` is `true`.
 *Effects:* As if by `x.swap(y)`.
+## Views <a id="views">[[views]]</a>
+### General <a id="views.general">[[views.general]]</a>
+The header `<span>` defines the view `span`.
+### Header `<span>` synopsis <a id="span.syn">[[span.syn]]</a>
+``` cpp
+namespace std {
+  // constants
+  inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
+  // [views.span], class template span
+  template<class ElementType, size_t Extent = dynamic_extent>
+    class span;
+  template<class ElementType, size_t Extent>
+    inline constexpr bool ranges::enable_view<span<ElementType, Extent>> =
+      Extent == 0 || Extent == dynamic_extent;
+  template<class ElementType, size_t Extent>
+    inline constexpr bool ranges::enable_borrowed_range<span<ElementType, Extent>> = true;
+  // [span.objectrep], views of object representation
+  template<class ElementType, size_t Extent>
+    span<const byte, Extent == dynamic_extent ? dynamic_extent : sizeof(ElementType) * Extent>
+      as_bytes(span<ElementType, Extent> s) noexcept;
+  template<class ElementType, size_t Extent>
+    span<byte, Extent == dynamic_extent ? dynamic_extent : sizeof(ElementType) * Extent>
+      as_writable_bytes(span<ElementType, Extent> s) noexcept;
+}
+```
+### Class template `span` <a id="views.span">[[views.span]]</a>
+#### Overview <a id="span.overview">[[span.overview]]</a>
+A `span` is a view over a contiguous sequence of objects, the storage of
+which is owned by some other object.
+All member functions of `span` have constant time complexity.
+``` cpp
+namespace std {
+  template<class ElementType, size_t Extent = dynamic_extent>
+  class span {
+  public:
+    // constants and types
+    using element_type = ElementType;
+    using value_type = remove_cv_t<ElementType>;
+    using size_type = size_t;
+    using difference_type = ptrdiff_t;
+    using pointer = element_type*;
+    using const_pointer = const element_type*;
+    using reference = element_type&;
+    using const_reference = const element_type&;
+    using iterator = implementation-defined  // type of span::iterator;        // see [span.iterators]
+    using reverse_iterator = std::reverse_iterator<iterator>;
+    static constexpr size_type extent = Extent;
+    // [span.cons], constructors, copy, and assignment
+    constexpr span() noexcept;
+    template<class It>
+      constexpr explicit(extent != dynamic_extent) span(It first, size_type count);
+    template<class It, class End>
+      constexpr explicit(extent != dynamic_extent) span(It first, End last);
+    template<size_t N>
+      constexpr span(type_identity_t<element_type> (&arr)[N]) noexcept;
+    template<class T, size_t N>
+      constexpr span(array<T, N>& arr) noexcept;
+    template<class T, size_t N>
+      constexpr span(const array<T, N>& arr) noexcept;
+    template<class R>
+      constexpr explicit(extent != dynamic_extent) span(R&& r);
+    constexpr span(const span& other) noexcept = default;
+    template<class OtherElementType, size_t OtherExtent>
+      constexpr explicit(see below) span(const span<OtherElementType, OtherExtent>& s) noexcept;
+    ~span() noexcept = default;
+    constexpr span& operator=(const span& other) noexcept = default;
+    // [span.sub], subviews
+    template<size_t Count>
+      constexpr span<element_type, Count> first() const;
+    template<size_t Count>
+      constexpr span<element_type, Count> last() const;
+    template<size_t Offset, size_t Count = dynamic_extent>
+      constexpr span<element_type, see below> subspan() const;
+    constexpr span<element_type, dynamic_extent> first(size_type count) const;
+    constexpr span<element_type, dynamic_extent> last(size_type count) const;
+    constexpr span<element_type, dynamic_extent> subspan(
+      size_type offset, size_type count = dynamic_extent) const;
+    // [span.obs], observers
+    constexpr size_type size() const noexcept;
+    constexpr size_type size_bytes() const noexcept;
+    [[nodiscard]] constexpr bool empty() const noexcept;
+    // [span.elem], element access
+    constexpr reference operator[](size_type idx) const;
+    constexpr reference front() const;
+    constexpr reference back() const;
+    constexpr pointer data() const noexcept;
+    // [span.iterators], iterator support
+    constexpr iterator begin() const noexcept;
+    constexpr iterator end() const noexcept;
+    constexpr reverse_iterator rbegin() const noexcept;
+    constexpr reverse_iterator rend() const noexcept;
+  private:
+    pointer data_;              // exposition only
+    size_type size_;            // exposition only
+  };
+  template<class It, class EndOrSize>
+    span(It, EndOrSize) -> span<remove_reference_t<iter_reference_t<It>>>;
+  template<class T, size_t N>
+    span(T (&)[N]) -> span<T, N>;
+  template<class T, size_t N>
+    span(array<T, N>&) -> span<T, N>;
+  template<class T, size_t N>
+    span(const array<T, N>&) -> span<const T, N>;
+  template<class R>
+    span(R&&) -> span<remove_reference_t<ranges::range_reference_t<R>>>;
+}
+```
+`ElementType` is required to be a complete object type that is not an
+abstract class type.
+#### Constructors, copy, and assignment <a id="span.cons">[[span.cons]]</a>
+``` cpp
+constexpr span() noexcept;
+```
+*Constraints:* `Extent == dynamic_extent || Extent == 0` is `true`.
+*Ensures:* `size() == 0 && data() == nullptr`.
+``` cpp
+template<class It>
+  constexpr explicit(extent != dynamic_extent) span(It first, size_type count);
+```
+*Constraints:* Let `U` be `remove_reference_t<iter_reference_t<It>>`.
+- `It` satisfies `contiguous_iterator`.
+- `is_convertible_v<U(*)[], element_type(*)[]>` is `true`.
+  \[*Note 1*: The intent is to allow only qualification conversions of
+  the iterator reference type to `element_type`. — *end note*]
+*Preconditions:*
+- \[`first`, `first + count`) is a valid range.
+- `It` models `contiguous_iterator`.
+- If `extent` is not equal to `dynamic_extent`, then `count` is equal to
+  `extent`.
+*Effects:* Initializes `data_` with `to_address(first)` and `size_` with
+`count`.
+*Throws:* Nothing.
+``` cpp
+template<class It, class End>
+  constexpr explicit(extent != dynamic_extent) span(It first, End last);
+```
+*Constraints:* Let `U` be `remove_reference_t<iter_reference_t<It>>`.
+- `is_convertible_v<U(*)[], element_type(*)[]>` is `true`.
+  \[*Note 2*: The intent is to allow only qualification conversions of
+  the iterator reference type to `element_type`. — *end note*]
+- `It` satisfies `contiguous_iterator`.
+- `End` satisfies `sized_sentinel_for<It>`.
+- `is_convertible_v<End, size_t>` is `false`.
+*Preconditions:*
+- If `extent` is not equal to `dynamic_extent`, then `last - first` is
+  equal to `extent`.
+- \[`first`, `last`) is a valid range.
+- `It` models `contiguous_iterator`.
+- `End` models `sized_sentinel_for<It>`.
+*Effects:* Initializes `data_` with `to_address(first)` and `size_` with
+`last - first`.
+*Throws:* When and what `last - first` throws.
+``` cpp
+template<size_t N> constexpr span(type_identity_t<element_type> (&arr)[N]) noexcept;
+template<class T, size_t N> constexpr span(array<T, N>& arr) noexcept;
+template<class T, size_t N> constexpr span(const array<T, N>& arr) noexcept;
+```
+*Constraints:* Let `U` be `remove_pointer_t<decltype(data(arr))>`.
+- `extent == dynamic_extent || N == extent` is `true`, and
+- `is_convertible_v<U(*)[], element_type(*)[]>` is `true`.
+  \[*Note 3*: The intent is to allow only qualification conversions of
+  the array element type to `element_type`. — *end note*]
+*Effects:* Constructs a `span` that is a view over the supplied array.
+[*Note 1*: `type_identity_t` affects class template argument
+deduction. — *end note*]
+*Ensures:* `size() == N && data() == data(arr)` is `true`.
+``` cpp
+template<class R> constexpr explicit(extent != dynamic_extent) span(R&& r);
+```
+*Constraints:* Let `U` be
+`remove_reference_t<ranges::range_reference_t<R>>`.
+- `R` satisfies `ranges::contiguous_range` and `ranges::sized_range`.
+- Either `R` satisfies `ranges::borrowed_range` or
+  `is_const_v<element_type>` is `true`.
+- `remove_cvref_t<R>` is not a specialization of `span`.
+- `remove_cvref_t<R>` is not a specialization of `array`.
+- `is_array_v<remove_cvref_t<R>>` is `false`.
+- `is_convertible_v<U(*)[], element_type(*)[]>` is `true`.
+  \[*Note 4*: The intent is to allow only qualification conversions of
+  the range reference type to `element_type`. — *end note*]
+*Preconditions:*
+- If `extent` is not equal to `dynamic_extent`, then `ranges::size(r)`
+  is equal to `extent`.
+- `R` models `ranges::contiguous_range` and `ranges::sized_range`.
+- If `is_const_v<element_type>` is `false`, `R` models
+  `ranges::borrowed_range`.
+*Effects:* Initializes `data_` with `ranges::data(r)` and `size_` with
+`ranges::size(r)`.
+*Throws:* What and when `ranges::data(r)` and `ranges::size(r)` throw.
+``` cpp
+constexpr span(const span& other) noexcept = default;
+```
+*Ensures:* `other.size() == size() && other.data() == data()`.
+``` cpp
+template<class OtherElementType, size_t OtherExtent>
+  constexpr explicit(see below) span(const span<OtherElementType, OtherExtent>& s) noexcept;
+```
+*Constraints:*
+- `extent == dynamic_extent` `||` `OtherExtent == dynamic_extent` `||`
+  `extent == OtherExtent` is `true`, and
+- `is_convertible_v<OtherElementType(*)[], element_type(*)[]>` is
+  `true`. \[*Note 5*: The intent is to allow only qualification
+  conversions of the `OtherElementType` to
+  `element_type`. — *end note*]
+*Preconditions:* If `extent` is not equal to `dynamic_extent`, then
+`s.size()` is equal to `extent`.
+*Effects:* Constructs a `span` that is a view over the range
+\[`s.data()`, `s.data() + s.size()`).
+*Ensures:* `size() == s.size() && data() == s.data()`.
+*Remarks:* The expression inside `explicit` is equivalent to:
+``` cpp
+extent != dynamic_extent && OtherExtent == dynamic_extent
+```
+``` cpp
+constexpr span& operator=(const span& other) noexcept = default;
+```
+*Ensures:* `size() == other.size() && data() == other.data()`.
+#### Deduction guides <a id="span.deduct">[[span.deduct]]</a>
+``` cpp
+template<class It, class EndOrSize>
+  span(It, EndOrSize) -> span<remove_reference_t<iter_reference_t<It>>>;
+```
+*Constraints:* `It` satisfies `contiguous_iterator`.
+``` cpp
+template<class R>
+  span(R&&) -> span<remove_reference_t<ranges::range_reference_t<R>>>;
+```
+*Constraints:* `R` satisfies `ranges::contiguous_range`.
+#### Subviews <a id="span.sub">[[span.sub]]</a>
+``` cpp
+template<size_t Count> constexpr span<element_type, Count> first() const;
+```
+*Mandates:* `Count <= Extent` is `true`.
+*Preconditions:* `Count <= size()` is `true`.
+*Effects:* Equivalent to: `return R{data(), Count};` where `R` is the
+return type.
+``` cpp
+template<size_t Count> constexpr span<element_type, Count> last() const;
+```
+*Mandates:* `Count <= Extent` is `true`.
+*Preconditions:* `Count <= size()` is `true`.
+*Effects:* Equivalent to: `return R{data() + (size() - Count), Count};`
+where `R` is the return type.
+``` cpp
+template<size_t Offset, size_t Count = dynamic_extent>
+  constexpr span<element_type, see below> subspan() const;
+```
+*Mandates:*
+``` cpp
+Offset <= Extent && (Count == dynamic_extent || Count <= Extent - Offset)
+```
+is `true`.
+*Preconditions:*
+``` cpp
+Offset <= size() && (Count == dynamic_extent || Count <= size() - Offset)
+```
+is `true`.
+*Effects:* Equivalent to:
+``` cpp
+return span<ElementType, see below>(
+  data() + Offset, Count != dynamic_extent ? Count : size() - Offset);
+```
+*Remarks:* The second template argument of the returned `span` type is:
+``` cpp
+Count != dynamic_extent ? Count
+                        : (Extent != dynamic_extent ? Extent - Offset
+                                                    : dynamic_extent)
+```
+``` cpp
+constexpr span<element_type, dynamic_extent> first(size_type count) const;
+```
+*Preconditions:* `count <= size()` is `true`.
+*Effects:* Equivalent to: `return {data(), count};`
+``` cpp
+constexpr span<element_type, dynamic_extent> last(size_type count) const;
+```
+*Preconditions:* `count <= size()` is `true`.
+*Effects:* Equivalent to: `return {data() + (size() - count), count};`
+``` cpp
+constexpr span<element_type, dynamic_extent> subspan(
+  size_type offset, size_type count = dynamic_extent) const;
+```
+*Preconditions:*
+``` cpp
+offset <= size() && (count == dynamic_extent || count <= size() - offset)
+```
+is `true`.
+*Effects:* Equivalent to:
+``` cpp
+return {data() + offset, count == dynamic_extent ? size() - offset : count};
+```
+#### Observers <a id="span.obs">[[span.obs]]</a>
+``` cpp
+constexpr size_type size() const noexcept;
+```
+*Effects:* Equivalent to: `return size_;`
+``` cpp
+constexpr size_type size_bytes() const noexcept;
+```
+*Effects:* Equivalent to: `return size() * sizeof(element_type);`
+``` cpp
+[[nodiscard]] constexpr bool empty() const noexcept;
+```
+*Effects:* Equivalent to: `return size() == 0;`
+#### Element access <a id="span.elem">[[span.elem]]</a>
+``` cpp
+constexpr reference operator[](size_type idx) const;
+```
+*Preconditions:* `idx < size()` is `true`.
+*Effects:* Equivalent to: `return *(data() + idx);`
+``` cpp
+constexpr reference front() const;
+```
+*Preconditions:* `empty()` is `false`.
+*Effects:* Equivalent to: `return *data();`
+``` cpp
+constexpr reference back() const;
+```
+*Preconditions:* `empty()` is `false`.
+*Effects:* Equivalent to: `return *(data() + (size() - 1));`
+``` cpp
+constexpr pointer data() const noexcept;
+```
+*Effects:* Equivalent to: `return data_;`
+#### Iterator support <a id="span.iterators">[[span.iterators]]</a>
+``` cpp
+using iterator = implementation-defined  // type of span::iterator;
+```
+The type models `contiguous_iterator` [[iterator.concept.contiguous]],
+meets the *Cpp17RandomAccessIterator*
+requirements [[random.access.iterators]], and meets the requirements for
+constexpr iterators [[iterator.requirements.general]]. All requirements
+on container iterators [[container.requirements]] apply to
+`span::iterator` as well.
+``` cpp
+constexpr iterator begin() const noexcept;
+```
+*Returns:* An iterator referring to the first element in the span. If
+`empty()` is `true`, then it returns the same value as `end()`.
+``` cpp
+constexpr iterator end() const noexcept;
+```
+*Returns:* An iterator which is the past-the-end value.
+``` cpp
+constexpr reverse_iterator rbegin() const noexcept;
+```
+*Effects:* Equivalent to: `return reverse_iterator(end());`
+``` cpp
+constexpr reverse_iterator rend() const noexcept;
+```
+*Effects:* Equivalent to: `return reverse_iterator(begin());`
+#### Views of object representation <a id="span.objectrep">[[span.objectrep]]</a>
+``` cpp
+template<class ElementType, size_t Extent>
+  span<const byte, Extent == dynamic_extent ? dynamic_extent : sizeof(ElementType) * Extent>
+    as_bytes(span<ElementType, Extent> s) noexcept;
+```
+*Effects:* Equivalent to:
+`return R{reinterpret_cast<const byte*>(s.data()), s.size_bytes()};`
+where `R` is the return type.
+``` cpp
+template<class ElementType, size_t Extent>
+  span<byte, Extent == dynamic_extent ? dynamic_extent : sizeof(ElementType) * Extent>
+    as_writable_bytes(span<ElementType, Extent> s) noexcept;
+```
+*Constraints:* `is_const_v<ElementType>` is `false`.
+*Effects:* Equivalent to:
+`return R{reinterpret_cast<byte*>(s.data()), s.size_bytes()};` where `R`
+is the return type.
 <!-- Link reference definitions -->
 [alg.sorting]: algorithms.md#alg.sorting
 [algorithm.stable]: library.md#algorithm.stable
 [algorithms]: algorithms.md#algorithms
+[algorithms.requirements]: algorithms.md#algorithms.requirements
 [allocator.requirements]: library.md#allocator.requirements
 [allocator.requirements.completeness]: library.md#allocator.requirements.completeness
 [allocator.traits.members]: utilities.md#allocator.traits.members
 [array]: #array
 [array.cons]: #array.cons
+[array.creation]: #array.creation
+[array.members]: #array.members
 [array.overview]: #array.overview
 [array.special]: #array.special
 [array.syn]: #array.syn
 [array.tuple]: #array.tuple
 [array.zero]: #array.zero
 [associative]: #associative
 [associative.general]: #associative.general
 [associative.map.syn]: #associative.map.syn
 [associative.reqmts]: #associative.reqmts
 [associative.reqmts.except]: #associative.reqmts.except
 [associative.set.syn]: #associative.set.syn
 [basic.string]: strings.md#basic.string
+[class.copy.ctor]: class.md#class.copy.ctor
+[class.default.ctor]: class.md#class.default.ctor
+[class.dtor]: class.md#class.dtor
 [container.adaptors]: #container.adaptors
 [container.adaptors.general]: #container.adaptors.general
+[container.alloc.req]: #container.alloc.req
+[container.assoc.req]: #container.assoc.req
+[container.hash.req]: #container.hash.req
 [container.insert.return]: #container.insert.return
 [container.node]: #container.node
+[container.node.compat]: #container.node.compat
 [container.node.cons]: #container.node.cons
 [container.node.dtor]: #container.node.dtor
 [container.node.modifiers]: #container.node.modifiers
 [container.node.observers]: #container.node.observers
 [container.node.overview]: #container.node.overview
+[container.opt]: #container.opt
+[container.req]: #container.req
 [container.requirements]: #container.requirements
 [container.requirements.dataraces]: #container.requirements.dataraces
 [container.requirements.general]: #container.requirements.general
+[container.rev.req]: #container.rev.req
+[container.seq.opt]: #container.seq.opt
+[container.seq.req]: #container.seq.req
 [containers]: #containers
 [containers.general]: #containers.general
+[containers.summary]: #containers.summary
 [dcl.init.aggr]: dcl.md#dcl.init.aggr
 [deque]: #deque
 [deque.capacity]: #deque.capacity
 [deque.cons]: #deque.cons
+[deque.erasure]: #deque.erasure
 [deque.modifiers]: #deque.modifiers
 [deque.overview]: #deque.overview
 [deque.syn]: #deque.syn
+[forward.list.erasure]: #forward.list.erasure
+[forward.list.syn]: #forward.list.syn
 [forwardlist]: #forwardlist
 [forwardlist.access]: #forwardlist.access
 [forwardlist.cons]: #forwardlist.cons
 [forwardlist.iter]: #forwardlist.iter
 [forwardlist.modifiers]: #forwardlist.modifiers
 [forwardlist.ops]: #forwardlist.ops
 [forwardlist.overview]: #forwardlist.overview
 [hash.requirements]: library.md#hash.requirements
+[iterator.concept.contiguous]: iterators.md#iterator.concept.contiguous
 [iterator.requirements]: iterators.md#iterator.requirements
 [iterator.requirements.general]: iterators.md#iterator.requirements.general
 [list]: #list
 [list.capacity]: #list.capacity
 [list.cons]: #list.cons
+[list.erasure]: #list.erasure
 [list.modifiers]: #list.modifiers
 [list.ops]: #list.ops
 [list.overview]: #list.overview
 [list.syn]: #list.syn
 [map]: #map
 [map.access]: #map.access
 [map.cons]: #map.cons
+[map.erasure]: #map.erasure
 [map.modifiers]: #map.modifiers
 [map.overview]: #map.overview
 [multimap]: #multimap
 [multimap.cons]: #multimap.cons
+[multimap.erasure]: #multimap.erasure
 [multimap.modifiers]: #multimap.modifiers
 [multimap.overview]: #multimap.overview
 [multiset]: #multiset
 [multiset.cons]: #multiset.cons
+[multiset.erasure]: #multiset.erasure
 [multiset.overview]: #multiset.overview
 [priority.queue]: #priority.queue
 [priqueue.cons]: #priqueue.cons
 [priqueue.cons.alloc]: #priqueue.cons.alloc
 [priqueue.members]: #priqueue.members
+[priqueue.overview]: #priqueue.overview
 [priqueue.special]: #priqueue.special
 [queue]: #queue
 [queue.cons]: #queue.cons
 [queue.cons.alloc]: #queue.cons.alloc
 [queue.defn]: #queue.defn
 [sequence.reqmts]: #sequence.reqmts
 [sequences]: #sequences
 [sequences.general]: #sequences.general
 [set]: #set
 [set.cons]: #set.cons
+[set.erasure]: #set.erasure
 [set.overview]: #set.overview
+[span.cons]: #span.cons
+[span.deduct]: #span.deduct
+[span.elem]: #span.elem
+[span.iterators]: #span.iterators
+[span.objectrep]: #span.objectrep
+[span.obs]: #span.obs
+[span.overview]: #span.overview
+[span.sub]: #span.sub
+[span.syn]: #span.syn
 [stack]: #stack
 [stack.cons]: #stack.cons
 [stack.cons.alloc]: #stack.cons.alloc
 [stack.defn]: #stack.defn
 [stack.ops]: #stack.ops
 [stack.special]: #stack.special
 [stack.syn]: #stack.syn
 [strings]: strings.md#strings
 [swappable.requirements]: library.md#swappable.requirements
+[tab:container.opt]: #tab:container.opt
+[tab:container.req]: #tab:container.req
+[tab:container.rev.req]: #tab:container.rev.req
+[tab:container.seq.opt]: #tab:container.seq.opt
+[tab:container.seq.req]: #tab:container.seq.req
 [temp.deduct]: temp.md#temp.deduct
+[temp.param]: temp.md#temp.param
+[temp.type]: temp.md#temp.type
 [unord]: #unord
 [unord.general]: #unord.general
 [unord.hash]: utilities.md#unord.hash
 [unord.map]: #unord.map
 [unord.map.cnstr]: #unord.map.cnstr
 [unord.map.elem]: #unord.map.elem
+[unord.map.erasure]: #unord.map.erasure
 [unord.map.modifiers]: #unord.map.modifiers
 [unord.map.overview]: #unord.map.overview
 [unord.map.syn]: #unord.map.syn
 [unord.multimap]: #unord.multimap
 [unord.multimap.cnstr]: #unord.multimap.cnstr
+[unord.multimap.erasure]: #unord.multimap.erasure
 [unord.multimap.modifiers]: #unord.multimap.modifiers
 [unord.multimap.overview]: #unord.multimap.overview
 [unord.multiset]: #unord.multiset
 [unord.multiset.cnstr]: #unord.multiset.cnstr
+[unord.multiset.erasure]: #unord.multiset.erasure
 [unord.multiset.overview]: #unord.multiset.overview
 [unord.req]: #unord.req
 [unord.req.except]: #unord.req.except
 [unord.set]: #unord.set
 [unord.set.cnstr]: #unord.set.cnstr
+[unord.set.erasure]: #unord.set.erasure
 [unord.set.overview]: #unord.set.overview
 [unord.set.syn]: #unord.set.syn
 [vector]: #vector
 [vector.bool]: #vector.bool
 [vector.capacity]: #vector.capacity
 [vector.cons]: #vector.cons
 [vector.data]: #vector.data
+[vector.erasure]: #vector.erasure
 [vector.modifiers]: #vector.modifiers
 [vector.overview]: #vector.overview
 [vector.syn]: #vector.syn
+[views]: #views
+[views.general]: #views.general
+[views.span]: #views.span
 [^1]: Equality comparison is a refinement of partitioning if no two
     objects that compare equal fall into different partitions.
 [^2]: These member functions are only provided by containers whose

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