# std::same_as

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< cpp‎ | concepts

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

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]

### References

- C++23 standard (ISO/IEC 14882:2024):

  - 18.4.2 Concept `same_as` [concept.same]

- C++20 standard (ISO/IEC 14882:2020):

  - 18.4.2 Concept `same_as` [concept.same]

### See also

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

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