tmp/tmp0zqf2w2r/{from.md → to.md}
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| 1 |
+
### Specializations for floating-point types <a id="atomics.ref.float">[[atomics.ref.float]]</a>
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There are specializations of the `atomic_ref` class template for the
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floating-point types `float`, `double`, and `long double`. For each such
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type `floating-point`, the specialization `atomic_ref<floating-point>`
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provides additional atomic operations appropriate to floating-point
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types.
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``` cpp
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+
namespace std {
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template<> struct atomic_ref<floating-point> {
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private:
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floating-point* ptr; // exposition only
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public:
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using value_type = floating-point;
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using difference_type = value_type;
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static constexpr size_t required_alignment = implementation-defined // required alignment for atomic_ref type's operations;
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static constexpr bool is_always_lock_free = implementation-defined // whether a given atomic_ref type's operations are always lock free;
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bool is_lock_free() const noexcept;
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explicit atomic_ref(floating-point&);
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atomic_ref(const atomic_ref&) noexcept;
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atomic_ref& operator=(const atomic_ref&) = delete;
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void store(floating-point, memory_order = memory_order::seq_cst) const noexcept;
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floating-point operator=(floating-point) const noexcept;
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floating-point load(memory_order = memory_order::seq_cst) const noexcept;
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operator floating-point() const noexcept;
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floating-point exchange(floating-point,
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memory_order = memory_order::seq_cst) const noexcept;
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bool compare_exchange_weak(floating-point&, floating-point,
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memory_order, memory_order) const noexcept;
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bool compare_exchange_strong(floating-point&, floating-point,
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memory_order, memory_order) const noexcept;
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bool compare_exchange_weak(floating-point&, floating-point,
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memory_order = memory_order::seq_cst) const noexcept;
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bool compare_exchange_strong(floating-point&, floating-point,
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memory_order = memory_order::seq_cst) const noexcept;
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floating-point fetch_add(floating-point,
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memory_order = memory_order::seq_cst) const noexcept;
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floating-point fetch_sub(floating-point,
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memory_order = memory_order::seq_cst) const noexcept;
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floating-point operator+=(floating-point) const noexcept;
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floating-point operator-=(floating-point) const noexcept;
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void wait(floating-point, memory_order = memory_order::seq_cst) const noexcept;
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void notify_one() const noexcept;
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void notify_all() const noexcept;
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};
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}
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```
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Descriptions are provided below only for members that differ from the
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primary template.
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The following operations perform arithmetic computations. The key,
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| 61 |
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operator, and computation correspondence are identified in
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| 62 |
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[[atomic.types.int.comp]].
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``` cpp
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floating-point fetch_key(floating-point operand,
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memory_order order = memory_order::seq_cst) const noexcept;
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```
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| 68 |
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*Effects:* Atomically replaces the value referenced by `*ptr` with the
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result of the computation applied to the value referenced by `*ptr` and
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the given operand. Memory is affected according to the value of `order`.
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| 72 |
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These operations are atomic read-modify-write
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operations [[intro.races]].
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| 74 |
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| 75 |
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*Returns:* Atomically, the value referenced by `*ptr` immediately before
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| 76 |
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the effects.
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| 77 |
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| 78 |
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*Remarks:* If the result is not a representable value for its
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| 79 |
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type [[expr.pre]], the result is unspecified, but the operations
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| 80 |
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otherwise have no undefined behavior. Atomic arithmetic operations on
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| 81 |
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*`floating-point`* should conform to the
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| 82 |
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`std::numeric_limits<`*`floating-point`*`>` traits associated with the
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| 83 |
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floating-point type [[limits.syn]]. The floating-point
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| 84 |
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environment [[cfenv]] for atomic arithmetic operations on
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| 85 |
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*`floating-point`* may be different than the calling thread’s
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| 86 |
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floating-point environment.
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| 87 |
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| 88 |
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``` cpp
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| 89 |
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floating-point operator op=(floating-point operand) const noexcept;
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| 90 |
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```
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| 91 |
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| 92 |
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*Effects:* Equivalent to:
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| 93 |
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`return fetch_`*`key`*`(operand) `*`op`*` operand;`
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| 94 |
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