std::same_as
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Concepts library
same_as
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Exposition-only concepts
(C++20)
Defined in header
<concepts>
template< class T, class U >
concept same_as = /* see below */;
(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.
[edit] 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>;
[edit] Example
Run this code
#include <concepts> #include <iostream> template<typename T, typename ... U> concept either = (std::same_as<T, U> || ...); template<typename T> concept is_printable = std::integral <T> || std::floating_point <T> || either<std::remove_cvref_t <std::remove_pointer_t <std::decay_t <T>>>, char, wchar_t>; void println(is_printable 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]
[edit] References
- C++23 standard (ISO/IEC 14882:2024):
- 18.4.2 Concept
same_as[concept.same]
- 18.4.2 Concept
- C++20 standard (ISO/IEC 14882:2020):
- 18.4.2 Concept
same_as[concept.same]
- 18.4.2 Concept