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std::experimental::optional::value(3) C++ Standard Libary std::experimental::optional::value(3)

NAME

std::experimental::optional::value - std::experimental::optional::value

Synopsis


constexpr T& value() &; (1) (library fundamentals TS)
constexpr const T & value() const &;
constexpr T&& value() &&; (2) (library fundamentals TS)
constexpr const T&& value() const &&;


Returns the contained value.


1) Equivalent to return bool(*this) ? *val : throw bad_optional_access();.
2) Equivalent to return bool(*this) ? std::move(*val) : throw
bad_optional_access();.

Parameters


(none)

Return value


A reference to the contained value.

Exceptions


std::experimental::bad_optional_access if *this does not contain a value.

Notes


The dereference operator operator*() does not check if this optional contains a
value, which may be more efficient than value().

Example

// Run this code


#include <experimental/optional>
#include <iostream>


int main()
{
std::experimental::optional<int> opt = {};


try
{
int n = opt.value();
}
catch (const std::logic_error& e)
{
std::cout << e.what() << '\n';
}
}

Possible output:


optional<T>::value: not engaged

See also


returns the contained value if available, another value
value_or otherwise
(public member function)
operator-> accesses the contained value
operator* (public member function)
bad_optional_access exception indicating checked access to an optional that
(library fundamentals TS) doesn't contain a value
(class)

Category:


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2024.06.10 http://cppreference.com