std::saturating_add

#include <climits>
#include <limits>
#include <numeric>

static_assert(CHAR_BIT == 8);
static_assert(UCHAR_MAX == 255);

int main()
{
    constexpr int a = std::saturating_add(3, 4); // no saturation occurs, T = int
    static_assert(a == 7);

    constexpr unsigned char b = std::saturating_add<unsigned char>(UCHAR_MAX, 4); // saturated
    static_assert(b == UCHAR_MAX);

    constexpr unsigned char c = std::saturating_add(UCHAR_MAX, 4); // not saturated, T = int
        // saturating_add(int, int) returns int tmp == 259,
        // then assignment truncates 259 % 256 == 3 (might yield int -> unsigned char warning)
    static_assert(c == 3);

//  unsigned char d = std::saturating_add(252, c); // Error: inconsistent deductions for T

    constexpr unsigned char e = std::saturating_add<unsigned char>(251, a); // saturated
    static_assert(e == UCHAR_MAX);
        // 251 is of type T = unsigned char, `a` is converted to unsigned char value;
        // might yield an int -> unsigned char conversion warning for `a`

    constexpr signed char f = std::saturating_add<signed char>(-123, -3); // not saturated
    static_assert(f == -126);

    constexpr signed char g = std::saturating_add<signed char>(-123, -13); // saturated
    static_assert(g == std::numeric_limits<signed char>::min()); // g == -128
}