A valarray object is designed to hold an array of elements, and easily perform mathematical operations on them.

// valarray constructor example

#include <iostream>

#include <valarray>

using namespace std;

int main ()

{

  int init[]= {10,20,30,40};

  valarray<int> first;           // (empty)

  valarray<int> second (5);      // 0 0 0 0 0

  valarray<int> third (10,3);    // 10 10 10

  valarray<int> fourth (init,4); // 10 20 30 40

  valarray<int> fifth (fourth);  // 10 20 30 40

  cout << "fifth sums " << fifth.sum() << endl;

  return 0;

}

Output:

fifth sums 100

int init[]={10,20,30,40,50};  　valarray
    
      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
    

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

每个元素都按照(１+n)%size() 这种方式旋转

int increment (int x) {
   return ++x;}

int init[]={10,20,30,40,50};  　valarray
    
      foo (init,5); 　 valarray
     
       bar = foo.apply(increment);  　for (size_t n=0; n
     
    

Output:

11 21 31 41 51