22 General utilities library [utilities]

22.8 Expected objects [expected]

22.8.6 Class template expected [expected.expected]

22.8.6.6 Observers [expected.object.obs]

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constexpr const T* operator->() const noexcept; constexpr T* operator->() noexcept;
1
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Preconditions: has_value() is true.
2
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Returns: addressof(val).
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constexpr const T& operator*() const & noexcept; constexpr T& operator*() & noexcept;
3
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Preconditions: has_value() is true.
4
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Returns: val.
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constexpr T&& operator*() && noexcept; constexpr const T&& operator*() const && noexcept;
5
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Preconditions: has_value() is true.
6
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Returns: std​::​move(val).
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constexpr explicit operator bool() const noexcept; constexpr bool has_value() const noexcept;
7
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Returns: has_val.
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constexpr const T& value() const &; constexpr T& value() &;
8
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Mandates: is_copy_constructible_v<E> is true.
9
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Returns: val, if has_value() is true.
10
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Throws: bad_expected_access(as_const(error())) if has_value() is false.
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constexpr T&& value() &&; constexpr const T&& value() const &&;
11
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Mandates: is_copy_constructible_v<E> is true and is_constructible_v<E, decltype(std​::​move(error()))> is true.
12
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Returns: std​::​move(val), if has_value() is true.
13
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Throws: bad_expected_access(std​::​move(error())) if has_value() is false.
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constexpr const E& error() const & noexcept; constexpr E& error() & noexcept;
14
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Preconditions: has_value() is false.
15
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Returns: unex.
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constexpr E&& error() && noexcept; constexpr const E&& error() const && noexcept;
16
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Preconditions: has_value() is false.
17
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Returns: std​::​move(unex).
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template<class U> constexpr T value_or(U&& v) const &;
18
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Mandates: is_copy_constructible_v<T> is true and is_convertible_v<U, T> is true.
19
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Returns: has_value() ? **this : static_cast<T>(std​::​forward<U>(v)).
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template<class U> constexpr T value_or(U&& v) &&;
20
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Mandates: is_move_constructible_v<T> is true and is_convertible_v<U, T> is true.
21
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Returns: has_value() ? std​::​move(**this) : static_cast<T>(std​::​forward<U>(v)).
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template<class G = E> constexpr E error_or(G&& e) const &;
22
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Mandates: is_copy_constructible_v<E> is true and is_convertible_v<G, E> is true.
23
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Returns: std​::​forward<G>(e) if has_value() is true, error() otherwise.
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template<class G = E> constexpr E error_or(G&& e) &&;
24
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Mandates: is_move_constructible_v<E> is true and is_convertible_v<G, E> is true.
25
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Returns: std​::​forward<G>(e) if has_value() is true, std​::​move(error()) otherwise.