cppdraft_translate/cppdraft/expected/object/obs.md

[expected.object.obs]

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;

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Hardened preconditions: has_value() is true.

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Returns: addressof(val).

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constexpr const T& operator*() const & noexcept; constexpr T& operator*() & noexcept;

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Hardened preconditions: has_value() is true.

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Returns: val.

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constexpr T&& operator*() && noexcept; constexpr const T&& operator*() const && noexcept;

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Hardened preconditions: has_value() is true.

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Returns: std​::​move(val).

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constexpr explicit operator bool() const noexcept; constexpr bool has_value() const noexcept;

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Returns: has_val.

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constexpr const T& value() const &; constexpr T& value() &;

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Mandates: is_copy_constructible_v is true.

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Returns: val, if has_value() is true.

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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 &&;

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Mandates: is_copy_constructible_v is true andis_constructible_v<E, decltype(std​::​move(error()))> is true.

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Returns: std​::​move(val), if has_value() is true.

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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;

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Hardened preconditions: has_value() is false.

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Returns: unex.

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constexpr E&& error() && noexcept; constexpr const E&& error() const && noexcept;

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Hardened preconditions: has_value() is false.

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Returns: std​::​move(unex).

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template<class U = remove_cv_t<T>> constexpr T value_or(U&& v) const &;

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Mandates: is_copy_constructible_v is true andis_convertible_v<U, T> is true.

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Returns: has_value() ? **this : static_cast(std​::​forward(v)).

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template<class U = remove_cv_t<T>> constexpr T value_or(U&& v) &&;

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Mandates: is_move_constructible_v is true andis_convertible_v<U, T> is true.

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Returns: has_value() ? std​::​move(**this) : static_cast(std​::​forward(v)).

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template<class G = E> constexpr E error_or(G&& e) const &;

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Mandates: is_copy_constructible_v is true andis_convertible_v<G, E> is true.

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Returns: std​::​forward(e) if has_value() is true,error() otherwise.

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template<class G = E> constexpr E error_or(G&& e) &&;

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Mandates: is_move_constructible_v is true andis_convertible_v<G, E> is true.

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Returns: std​::​forward(e) if has_value() is true,std​::​move(error()) otherwise.