Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help 
std::valarray::apply(3)	      C++ Standard Libary      std::valarray::apply(3)

NAME
       std::valarray::apply - std::valarray::apply

Synopsis
	  valarray<T> apply( T func(T) ) const;
	  valarray<T> apply( T func(const T&) )	const;

	  Returns  a  new  valarray of the same	size with values which are ac-
       quired by applying
	  function func	to the previous	values of the elements.

Parameters
	  func - function to apply to the values

Return value
	  The resulting	valarray with values  acquired	by  applying  function
       func.

Notes
	  The  function	can be implemented with	the return type	different from
       std::valarray.
	  In this case,	the replacement	type has the following properties:

		     * All const member	functions of  std::valarray  are  pro-
       vided.
		     *	 std::valarray,	 std::slice_array,  std::gslice_array,
       std::mask_array and
		       std::indirect_array can be  constructed	from  the  re-
       placement type.
		     *	All  functions	accepting  an  argument	 of type const
       std::valarray&
		       except begin() and end()
		       (since C++11) should also accept	the replacement	type.
		     * All functions accepting two  arguments  of  type	 const
       std::valarray&
		       should accept every combination of const	std::valarray&
       and the
		       replacement type.
		     *	The  return  type does not add more than two levels of
       template	nesting
		       over the	most deeply-nested argument type.

Possible implementation
	  Following straightforward implementations can	be replaced by expres-
       sion templates
	  for a	higher efficiency.

	  template<class T>
	  valarray<T> valarray<T>::apply( T func(T) ) const
	  {
	      valarray<T> other	= *this;
	      for (T &i	: other) {
		  i = func(i);
	      }
	      return other;
	  }

	  template<class T>
	  valarray<T> valarray<T>::apply( T func(const T&) ) const
	  {
	      valarray<T> other	= *this;
	      for (T &i	: other) {
		  i = func(i);
	      }
	      return other;
	  }

Example
	  calculates and prints	the first 10 factorials

       // Run this code

	#include <iostream>
	#include <valarray>
	#include <cmath>

	int main()
	{
	    std::valarray<int> v = {1,2,3,4,5,6,7,8,9,10};
	    v =	v.apply([](int n)->int {
			    return std::round(std::tgamma(n+1));
			});
	    for(auto n : v) {
		std::cout << n << ' ';
	    }
	    std::cout << '\n';
	}

Output:
	1 2 6 24 120 720 5040 40320 362880 3628800

See also
	  for_each	   applies a function to a range of elements
			   (function template)
	  ranges::for_each applies a function to a range of elements
	  (C++20)	   (niebloid)

http://cppreference.com		  2022.07.31	       std::valarray::apply(3)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=std::valarray::apply&sektion=3&manpath=FreeBSD+Ports+15.0>

home | help