20 General utilities library [utilities]

20.6 Optional objects [optional]

20.6.3 Class template optional [optional.optional]

20.6.3.5 Observers [optional.observe]

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constexpr const T* operator->() const; constexpr T* operator->();
1
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Preconditions: *this contains a value.
2
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Returns: val.
3
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Throws: Nothing.
4
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Remarks: These functions are constexpr functions.
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constexpr const T& operator*() const&; constexpr T& operator*() &;
5
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Preconditions: *this contains a value.
6
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Returns: *val.
7
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Throws: Nothing.
8
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Remarks: These functions are constexpr functions.
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constexpr T&& operator*() &&; constexpr const T&& operator*() const&&;
9
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Preconditions: *this contains a value.
10
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Effects: Equivalent to: return std​::​move(*val);
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constexpr explicit operator bool() const noexcept;
11
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Returns: true if and only if *this contains a value.
12
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Remarks: This function is a constexpr function.
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constexpr bool has_value() const noexcept;
13
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Returns: true if and only if *this contains a value.
14
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Remarks: This function is a constexpr function.
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constexpr const T& value() const&; constexpr T& value() &;
15
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Effects: Equivalent to: 
return bool(*this) ? *val : throw bad_optional_access();
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constexpr T&& value() &&; constexpr const T&& value() const&&;
16
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Effects: Equivalent to: 
return bool(*this) ? std::move(*val) : throw bad_optional_access();
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template<class U> constexpr T value_or(U&& v) const&;
17
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Mandates: is_­copy_­constructible_­v<T> && is_­convertible_­v<U&&, T> is true.
18
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Effects: Equivalent to: 
return bool(*this) ? **this : static_cast<T>(std::forward<U>(v));
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template<class U> constexpr T value_or(U&& v) &&;
19
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Mandates: is_­move_­constructible_­v<T> && is_­convertible_­v<U&&, T> is true.
20
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Effects: Equivalent to: 
return bool(*this) ? std::move(**this) : static_cast<T>(std::forward<U>(v));