std::abs(std::valarray) (3) - Linux Manuals

std::abs(std::valarray): std::abs(std::valarray)

NAME

std::abs(std::valarray) - std::abs(std::valarray)

Synopsis

Defined in header <valarray>
template< class T >
valarray<T> abs( const valarray<T>& va );

Computes absolute value of each element in the value array.

Parameters

va - value array to apply the operation to

Return value

Value array containing absolute values of the values in va.

Notes

Unqualified function (abs) is used to perform the computation. If such function is not available, std::abs is used due to argument dependent lookup.
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 provided.
      * std::valarray, std::slice_array, std::gslice_array, std::mask_array and std::indirect_array can be constructed from the replacement 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

  template< class T >
  valarray<T> abs( const valarray<T>& va )
  {
      valarray<T> other = va;
      for (T &i : other) {
          i = abs(i);
      }
      return other; // proxy object may be returned
  }

Example

// Run this code

  #include <valarray>
  #include <iostream>

  int main()
  {
      std::valarray<int> v{1, -2, 3, -4, 5, -6, 7, -8};
      std::valarray<int> v2 = std::abs(v);
      for(auto n : v2) {
          std::cout << n << ' ';
      }
      std::cout << '\n';
  }

Output:

  1 2 3 4 5 6 7 8