std::add_sat - cppreference.com (original) (raw)

| | | | | --------------------------------------------------------------- | | ------------- | | template< class T > constexpr T add_sat( T x, T y ) noexcept; | | (since C++26) |

Computes the saturating addition x + y. This operation (unlike built-in arithmetic operations on integers) behaves as-if it is a mathematical operation with an infinite range. Let _q_ denote the result of such operation. Returns:

• _q_, if _q_ is representable as a value of type T. Otherwise,
• the largest or smallest value of type T, whichever is closer to the _q_.

This overload participates in overload resolution only if T is an integer type, that is: signed char, short, int, long, long long, an extended signed integer type, or an unsigned version of such types. In particular, T must not be (possibly cv-qualified) bool, char, wchar_t, char8_t, char16_t, and char32_t, as these types are not intended for arithmetic.

Contents

• 1 Parameters
• 2 Return value
• 3 Notes
• 4 Possible implementation
• 5 Example
• 6 See also
• 7 External links

[edit] Parameters

[edit] Return value

Saturated x + y.

[edit] Notes

Unlike the built-in arithmetic operators on integers, the integral promotion does not apply to the x and y arguments.

If two arguments of different type are passed, the call fails to compile, i.e. the behavior relative to template argument deduction is the same as for std::min or std::max.

Most modern hardware architectures have efficient support for saturation arithmetic on SIMD vectors, including SSE2 for x86 and NEON for ARM.

[edit] Possible implementation

See libstdc++ (gcc).

[edit] Example

Can be previewed on Compiler Explorer.

#include #include #include   static_assert(CHAR_BIT == 8); static_assert(UCHAR_MAX == 255);   int main() { constexpr int a = std::add_sat(3, 4); // no saturation occurs, T = int static_assert(a == 7);   constexpr unsigned char b = std::add_sat(UCHAR_MAX, 4); // saturated static_assert(b == UCHAR_MAX);   constexpr unsigned char c = std::add_sat(UCHAR_MAX, 4); // not saturated, T = int // add_sat(int, int) returns int tmp == 259, // then assignment truncates 259 % 256 == 3 static_assert(c == 3);   // unsigned char d = std::add_sat(252, c); // Error: inconsistent deductions for T   constexpr unsigned char e = std::add_sat(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::add_sat(-123, -3); // not saturated static_assert(f == -126);   constexpr signed char g = std::add_sat(-123, -13); // saturated static_assert(g == std::numeric_limits::min()); // g == -128 }

[edit] See also

[edit] External links