NAME¶

std::same_as - std::same_as

Synopsis¶

Defined in header <concepts>
template< class T, class U > (since C++20)
concept same_as = /* see below */;

The concept same_as<T, U> is satisfied if and only if T and U denote the same type.

std::same_as<T, U> subsumes std::same_as<U, T> and vice versa.

Possible implementation¶

namespace detail
{
template< class T, class U >
concept SameHelper = std::is_same_v<T, U>;
}

template< class T, class U >
concept same_as = detail::SameHelper<T, U> && detail::SameHelper<U, T>;

Example¶

// Run this code

#include <concepts>
#include <iostream>

template<typename T, typename ... U>
concept IsAnyOf = (std::same_as<T, U> || ...);

template<typename T>
concept IsPrintable = std::integral<T> || std::floating_point<T> ||
IsAnyOf<std::remove_cvref_t<std::remove_pointer_t<std::decay_t<T>>>, char, wchar_t>;

void println(IsPrintable auto const ... arguments)
{
(std::wcout << ... << arguments) << '\n';
}

int main()
{
println("Example: ", 3.14, " : ", 42, " : [", 'a', L'-', L"Z]");
}

Output:¶

Example: 3.14 : 42 : [a-Z]

See also¶

is_same checks if two types are the same
(C++11) (class template)