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Showing content from https://cplusplus.com/valarray::cshift below:

public member function

<valarray>

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 
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// 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.

See also
valarray::shift
Shift elements (public member function)
valarray operators
Valarray operators (function)

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