std::experimental::optional<T>::value
From cppreference.com
constexpr T& value() &;
constexpr const T & value() const &;
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(1) | (library fundamentals TS) |
constexpr T&& value() &&;
constexpr const T&& value() const &&;
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(2) | (library fundamentals TS) |
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