std::add_sat
Defined in header <numeric> | ||
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, ifqis representable as a value of typeT. Otherwise,- the largest or smallest value of type
T, whichever is closer to theq.
This overload participates in overload resolution only if T is an integer type, that is: signedchar, short, int, long, longlong, 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 |
[edit]Parameters
| x, y | - | integer values |
[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.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_saturation_arithmetic | 202311L | (C++26) | Saturation arithmetic |
[edit]Possible implementation
See libstdc++ (gcc).
[edit]Example
Can be previewed on Compiler Explorer.
#include <climits>#include <limits>#include <numeric> static_assert(CHAR_BIT==8); static_assert(UCHAR_MAX==255); int main(){constexprint a = std::add_sat(3, 4);// no saturation occurs, T = int static_assert(a ==7); constexprunsignedchar b = std::add_sat<unsignedchar>(UCHAR_MAX, 4);// saturated static_assert(b ==UCHAR_MAX); constexprunsignedchar 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 constexprunsignedchar e = std::add_sat<unsignedchar>(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` constexprsignedchar f = std::add_sat<signedchar>(-123, -3);// not saturated static_assert(f ==-126); constexprsignedchar g = std::add_sat<signedchar>(-123, -13);// saturated static_assert(g ==std::numeric_limits<signedchar>::min());// g == -128}
[edit]See also
(C++26) | saturating subtraction operation on two integers (function template) |
(C++26) | saturating multiplication operation on two integers (function template) |
(C++26) | saturating division operation on two integers (function template) |
(C++26) | returns an integer value clamped to the range of another integer type (function template) |
(C++17) | clamps a value between a pair of boundary values (function template) |
(C++20) | checks if an integer value is in the range of a given integer type (function template) |
[static] | returns the smallest finite value of the given non-floating-point type, or the smallest positive normal value of the given floating-point type (public static member function of std::numeric_limits<T>) |
[static] | returns the largest finite value of the given type (public static member function of std::numeric_limits<T>) |
[edit]External links
| 1. | A branch-free implementation of saturation arithmetic — Locklessinc.com, 2012 |
| 2. | C++ Weekly - Ep 459 - C++26's Saturating Math Operations — Youtube.com, 2024-12-16 |
