public member function

std::valarray::cshift

valarray cshift (int n) const;

Circularly shift elements

Returns a copy of the valarray object with its elements rotated left n spaces (or right if n is negative).

The valarray returned has the same length as *this.

By cyclically shifting (rotating) an array, the I-th element in the resulting valarray corresponds to the element with position (I+n)%size() in the original valarray.

Unlike valarray::shift, the valarray returned by cshift does not initialize new elements with their default constructor to fill the last n elements in *this (or the first -n elements if n is negative). Instead, it uses the first (or last) elements of *this.

Parameters

n: Number of elements to rotate. If positive, it is rotated left. If negative, it is rotated right.

Return value

A new valarray object with the elements of *this rotated n spaces left.

Example

// valarray::cshift example
#include <iostream>     // std::cout
#include <cstddef>      // std::size_t
#include <valarray>     // std::valarray

int main ()
{
  int init[]={10,20,30,40,50};

  std::valarray<int> myvalarray (init,5);   // 10 20 30 40 50
  myvalarray = myvalarray.cshift(2);   // 30 40 50 10 20
  myvalarray = myvalarray.cshift(-1);  // 20 30 40 50 10

  std::cout << "myvalarray contains:";
  for (std::size_t n=0; n<myvalarray.size(); n++)
	  std::cout << ' ' << myvalarray[n];
  std::cout << '\n';

  return 0;
}

Output:


myvalarray contains: 20 30 40 50 10

Complexity

Depends on library implementation.

Iterator validity

No changes: Valid iterators, references and sub-arrays of the source valarray keep their validity.

Data races

Both the valarray and its elements are accessed.

Exception safety

If the function implementation constructs or assigns to elements, and any such operation throws an exception, it causes undefined behavior.
If the function needs to allocate internal storage and fails, it may throw an exception (such as bad_alloc), although this is not mandated.