std::add_sat
Defined in header <numeric>
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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
, ifq
is 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: 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 |
[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() { constexpr int a = std::add_sat(3, 4); // no saturation occurs, T = int static_assert(a == 7); constexpr unsigned char b = std::add_sat<unsigned char>(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<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::add_sat<signed char>(-123, -3); // not saturated static_assert(f == -126); constexpr signed char g = std::add_sat<signed char>(-123, -13); // saturated static_assert(g == std::numeric_limits<signed char>::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 a 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 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> )
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[edit] External links
1. | A branch-free implementation of saturation arithmetic — Locklessinc.com, 2012 |