tmp/tmpbo1h8nay/{from.md → to.md}
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| 1 |
+
#### General <a id="expected.void.general">[[expected.void.general]]</a>
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| 2 |
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| 3 |
+
``` cpp
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| 4 |
+
template<class T, class E> requires is_void_v<T>
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| 5 |
+
class expected<T, E> {
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| 6 |
+
public:
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| 7 |
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using value_type = T;
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| 8 |
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using error_type = E;
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using unexpected_type = unexpected<E>;
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| 10 |
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template<class U>
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+
using rebind = expected<U, error_type>;
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+
// [expected.void.cons], constructors
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| 15 |
+
constexpr expected() noexcept;
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| 16 |
+
constexpr expected(const expected&);
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| 17 |
+
constexpr expected(expected&&) noexcept(see below);
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template<class U, class G>
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constexpr explicit(see below) expected(const expected<U, G>&);
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template<class U, class G>
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constexpr explicit(see below) expected(expected<U, G>&&);
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| 22 |
+
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| 23 |
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template<class G>
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| 24 |
+
constexpr explicit(see below) expected(const unexpected<G>&);
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| 25 |
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template<class G>
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| 26 |
+
constexpr explicit(see below) expected(unexpected<G>&&);
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| 27 |
+
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| 28 |
+
constexpr explicit expected(in_place_t) noexcept;
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| 29 |
+
template<class... Args>
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| 30 |
+
constexpr explicit expected(unexpect_t, Args&&...);
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| 31 |
+
template<class U, class... Args>
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| 32 |
+
constexpr explicit expected(unexpect_t, initializer_list<U>, Args&&...);
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+
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+
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// [expected.void.dtor], destructor
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| 36 |
+
constexpr ~expected();
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| 37 |
+
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| 38 |
+
// [expected.void.assign], assignment
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| 39 |
+
constexpr expected& operator=(const expected&);
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| 40 |
+
constexpr expected& operator=(expected&&) noexcept(see below);
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| 41 |
+
template<class G>
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| 42 |
+
constexpr expected& operator=(const unexpected<G>&);
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| 43 |
+
template<class G>
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| 44 |
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constexpr expected& operator=(unexpected<G>&&);
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| 45 |
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constexpr void emplace() noexcept;
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| 46 |
+
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| 47 |
+
// [expected.void.swap], swap
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| 48 |
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constexpr void swap(expected&) noexcept(see below);
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| 49 |
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friend constexpr void swap(expected& x, expected& y) noexcept(noexcept(x.swap(y)));
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| 50 |
+
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| 51 |
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// [expected.void.obs], observers
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| 52 |
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constexpr explicit operator bool() const noexcept;
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| 53 |
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constexpr bool has_value() const noexcept;
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| 54 |
+
constexpr void operator*() const noexcept;
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| 55 |
+
constexpr void value() const &;
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| 56 |
+
constexpr void value() &&;
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| 57 |
+
constexpr const E& error() const & noexcept;
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| 58 |
+
constexpr E& error() & noexcept;
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| 59 |
+
constexpr const E&& error() const && noexcept;
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| 60 |
+
constexpr E&& error() && noexcept;
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| 61 |
+
template<class G = E> constexpr E error_or(G&&) const &;
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| 62 |
+
template<class G = E> constexpr E error_or(G&&) &&;
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| 63 |
+
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| 64 |
+
// [expected.void.monadic], monadic operations
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| 65 |
+
template<class F> constexpr auto and_then(F&& f) &;
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| 66 |
+
template<class F> constexpr auto and_then(F&& f) &&;
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| 67 |
+
template<class F> constexpr auto and_then(F&& f) const &;
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| 68 |
+
template<class F> constexpr auto and_then(F&& f) const &&;
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| 69 |
+
template<class F> constexpr auto or_else(F&& f) &;
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| 70 |
+
template<class F> constexpr auto or_else(F&& f) &&;
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| 71 |
+
template<class F> constexpr auto or_else(F&& f) const &;
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| 72 |
+
template<class F> constexpr auto or_else(F&& f) const &&;
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| 73 |
+
template<class F> constexpr auto transform(F&& f) &;
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| 74 |
+
template<class F> constexpr auto transform(F&& f) &&;
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| 75 |
+
template<class F> constexpr auto transform(F&& f) const &;
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| 76 |
+
template<class F> constexpr auto transform(F&& f) const &&;
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| 77 |
+
template<class F> constexpr auto transform_error(F&& f) &;
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| 78 |
+
template<class F> constexpr auto transform_error(F&& f) &&;
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| 79 |
+
template<class F> constexpr auto transform_error(F&& f) const &;
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| 80 |
+
template<class F> constexpr auto transform_error(F&& f) const &&;
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| 81 |
+
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| 82 |
+
// [expected.void.eq], equality operators
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| 83 |
+
template<class T2, class E2> requires is_void_v<T2>
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| 84 |
+
friend constexpr bool operator==(const expected& x, const expected<T2, E2>& y);
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| 85 |
+
template<class E2>
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| 86 |
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friend constexpr bool operator==(const expected&, const unexpected<E2>&);
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| 87 |
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| 88 |
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private:
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| 89 |
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bool has_val; // exposition only
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| 90 |
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union {
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| 91 |
+
E unex; // exposition only
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| 92 |
+
};
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| 93 |
+
};
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| 94 |
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```
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| 95 |
+
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| 96 |
+
Any object of type `expected<T, E>` either represents a value of type
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| 97 |
+
`T`, or contains a value of type `E` within its own storage.
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| 98 |
+
Implementations are not permitted to use additional storage, such as
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| 99 |
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dynamic memory, to allocate the object of type `E`. Member *`has_val`*
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| 100 |
+
indicates whether the `expected<T, E>` object represents a value of type
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| 101 |
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`T`.
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| 102 |
+
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| 103 |
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A program that instantiates the definition of the template
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| 104 |
+
`expected<T, E>` with a type for the `E` parameter that is not a valid
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| 105 |
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template argument for `unexpected` is ill-formed.
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| 106 |
+
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| 107 |
+
`E` shall meet the requirements of *Cpp17Destructible* (
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| 108 |
+
[[cpp17.destructible]]).
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| 109 |
+
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