std::in_range

template< class R, class T >
constexpr bool in_range( T t ) noexcept;

Returns true if the value of t is in the range of values that can be represented in R, that is, if t can be converted to R without data loss.

It is a compile-time error if either T or R is not a signed or unsigned integer type (including standard integer type and extended integer type).

Parameters

Return value

true if the value of t is representable in R, false otherwise.

Possible implementation

template<class R, class T>
constexpr bool in_range(T t) noexcept
{
    return std::cmp_greater_equal(t, std::numeric_limits<R>::min()) &&
        std::cmp_less_equal(t, std::numeric_limits<R>::max());
}

Notes

This function cannot be used with enums (including std::byte), char, char8_t, char16_t, char32_t, wchar_t and bool.

Example

#include <iostream>
#include <utility>
 
int main()
{
    std::cout << std::boolalpha;
 
    std::cout << std::in_range<std::size_t>(-1) << '\n';
    std::cout << std::in_range<std::size_t>(42) << '\n';
}

false
true

See also