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std::experi...e_expression(3) C++ Standard Libarystd::experi...e_expression(3)

NAME
       std::experimental::where_expression  - std::experimental::where_expres-
       sion

Synopsis
	  Defined in header <experimental/simd>
	  template< class M, class V >		 (parallelism TS v2)
	  class	where_expression;

	  The class template where_expression abstracts	the notion of selected
       elements	of a
	  given	lvalue of arithmetic or	data-parallel type. Selected  elements
       are the elements
	  of the lvalue	(of type V) for	which the corresponding	element	of the
       mask (of	type
	  M) is	true. Operators	applied	to objects of type where_expression<M,
       V> are applied
	  only to selected elements. All other elements	are left unchanged.

	  Use the where	function to construct where_expression objects.

Template parameters
	  M - The mask type
	  V - The value	type M applies on

	  Valid	combinations of	(M, V) are:

	    * (simd_mask<T, Abi>, simd<T, Abi>),
	    * (simd_mask<T, Abi>, simd_mask<T, Abi>),
	    * (bool, T).

Member functions
	  operator=   assigns to selected positions
		      (public member function)
	  operator+=
	  operator-=
	  operator*=
	  operator/=
	  operator%=  compound operators
	  operator&=  (public member function)
	  operator|=
	  operator^=
	  operator<<=
	  operator>>=
	  operator++  increment	and decrement operators
	  operator--  (public member function)
	  copy_from   loads from address to selected positions
		      (public member function)

Example
       // Run this code

	#include <cstddef>
	#include <experimental/simd>
	#include <iostream>
	namespace stdx = std::experimental;

	void print(auto	const& a)
	{
	    for	(std::size_t i{}; i != std::size(a); ++i)
		std::cout << a[i] << ' ';
	    std::cout << '\n';
	}

	template<class A>
	stdx::simd<int,	A> my_abs(stdx::simd<int, A> x)
	{
	    where(x < 0, x) = -x;
	    return x;
	}

	int main()
	{
	    const stdx::native_simd<int> a([](int i) { return i	- 2; });
	    print(a);
	    const auto b = my_abs(a);
	    print(b);
	}

Possible output:
	-2 -1 0	1
	2 1 0 1

http://cppreference.com		  2024.06.10	 std::experi...e_expression(3)

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