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

NAME
     std::experimental::where_expression - std::experimental::where_expression

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 el-
     ements 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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