cppdraft_translate/cppdraft/optional/observe.md

[optional.observe]

22 General utilities library [utilities]

22.5 Optional objects [optional]

22.5.3 Class template optional [optional.optional]

22.5.3.7 Observers [optional.observe]

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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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Remarks: These functions are constexpr functions.

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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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Remarks: These functions are constexpr functions.

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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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Effects: Equivalent to: return std​::​move(*val);

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constexpr explicit operator bool() const noexcept;

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Returns: true if and only if *this contains a value.

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Remarks: This function is a constexpr function.

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constexpr bool has_value() const noexcept;

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Returns: true if and only if *this contains a value.

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Remarks: This function is a constexpr function.

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

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Effects: Equivalent to:return has_value() ? *val : throw bad_optional_access();

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

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Effects: Equivalent to:return has_value() ? std::move(*val) : throw bad_optional_access();

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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_convertible_v<U&&, T> is true.

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Effects: Equivalent to:return 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_convertible_v<U&&, T> is true.

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Effects: Equivalent to:return has_value() ? std::move(**this) : static_cast(std::forward(v));