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    std::saturating_sub

    From cppreference.net
     
    C++
     
    Numerics library
     
    Saturation arithmetic
    Functions
    (C++26)
    (C++26)
    (C++26)
    (C++26)
    (C++26)
     
    Defined in header <numeric> 
    template< class T >
constexpr T saturating_sub( T x, T y ) noexcept;
    		(since C++26)

    Computes the saturating subtraction 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.

    Parameters

    x, y - integer values

    Return value

    Saturated x - y.

    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
    202603L (C++26) Renaming saturation arithmetic functions

    Possible implementation

    See libstdc++ (GCC), libc++ (Clang).

    Example

    Can be previewed on Compiler Explorer

    Run this code
    #include <climits>
#include <numeric>
 
static_assert
(""
    && (std::saturating_sub<int>(INT_MIN + 4, 3) == INT_MIN + 1) // not saturated
    && (std::saturating_sub<int>(INT_MIN + 4, 5) == INT_MIN) // saturated
    && (std::saturating_sub<int>(INT_MAX - 4, -3) == INT_MAX - 1) // not saturated
    && (std::saturating_sub<int>(INT_MAX - 4, -5) == INT_MAX) // saturated
    && (std::saturating_sub<unsigned>(4, 3) == 1) // not saturated
    && (std::saturating_sub<unsigned>(4, 5) == 0) // saturated
);

int main() {}

    See also

    (C++26)
    		 saturating addition 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 & algorithm function object)
    (C++20)
    (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>)

    External links

    1.  A branch-free implementation of saturation arithmetic — Locklessinc.com, 2012