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std::sub_sat(3) 	       C++ Standard Libary		 std::sub_sat(3)

NAME
     std::sub_sat - std::sub_sat

Synopsis
	Defined in header <numeric>
	template< class T >			   (since C++26)
	constexpr T sub_sat( T x, T y ) noexcept;

	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 inte-
     ger 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.

Exceptions
	Throws no exceptions.

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

	If two arguments of different type are passed, the call  fails	to  com-
     pile, 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

Possible implementation
	See libstdc++ (gcc).

Example
	Can be previewed on Compiler Explorer

     // Run this code

      #include <climits>
      #include <numeric>

      static_assert
      (""
	  && (std::sub_sat<int>(INT_MIN + 4, 3) == INT_MIN + 1) // not saturated
	  && (std::sub_sat<int>(INT_MIN + 4, 5) == INT_MIN) // saturated
	  && (std::sub_sat<int>(INT_MAX - 4, -3) == INT_MAX - 1)  //  not  satu-
     rated
	  && (std::sub_sat<int>(INT_MAX - 4, -5) == INT_MAX) // saturated
	  && (std::sub_sat<unsigned>(4, 3) == 1) // not saturated
	  && (std::sub_sat<unsigned>(4, 5) == 0) // saturated
      );

      int main() {}

See also
	add_sat       saturating addition operation on two integers
	(C++26)       (function template)
	mul_sat       saturating multiplication operation on two integers
	(C++26)       (function template)
	div_sat       saturating division operation on two integers
	(C++26)       (function template)
	saturate_cast returns an integer value clamped to the range of a another
     integer
	(C++26)       type
		      (function template)
	clamp	      clamps a value between a pair of boundary values
	(C++17)       (function template)
	in_range       checks if an integer value is in the range of a given in-
     teger type
	(C++20)       (function template)
	min	      returns the smallest finite value of the given type
	[static]      (public static member function of std::numeric_limits<T>)
	max	      returns the largest finite value of the given type
	[static]      (public static member function of std::numeric_limits<T>)

External links
	1.  A branch-free implementation of saturation	arithmetic  a  Lockless-
     inc.com, 2012

http://cppreference.com 	   2024.06.10			 std::sub_sat(3)
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