20 General utilities library [utilities]

20.6 Optional objects [optional]

20.6.3 Class template optional [optional.optional]

20.6.3.6 Observers [optional.observe]

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