C++ Tutorial/valarray/valarray subscript indexer

Assign value to valarray

<source lang="cpp">#include <iostream>

1. include <valarray>
2. include <cmath>

using namespace std;

int main() {

 valarray<int> v(10);
 int i;
  
 for(i=0; i<10; i++) v[i] = i;
  
 cout << "Original contents: ";
 for(i=0; i<10; i++)
   cout << v[i] << " ";
 cout << endl;
  
  
 return 0;

}</source>

Manipulate the value in a valarray

<source lang="cpp">/* The following code example is taken from the book

* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/

1. include <iostream>
2. include <valarray>

using namespace std; // print valarray template <class T> void printValarray (const valarray<T>& va) {

   for (int i=0; i<va.size(); i++) {
       cout << va[i] << " ";
   }
   cout << endl;

} int main() {

   // create and initialize valarray with nine elements
   valarray<double> va(9);
   for (int i=0; i<va.size(); i++) {
       va[i] = i * 1.1;
   }
   // print valarray
   printValarray(va);
   // double values in the valarray
   va *= 2.0;
   // print valarray again
   printValarray(va);
   // create second valarray initialized by the values of the first plus 10
   valarray<double> vb(va+10.0);
   // print second valarray
   printValarray(vb);
   // create third valarray as a result of processing both existing valarrays
   valarray<double> vc;
   vc = sqrt(va) + vb/2.0 - 1.0;
   
   // print third valarray
   printValarray(vc);

}</source>

0 1.1 2.2 3.3 4.4 5.5 6.6 7.7 8.8
0 2.2 4.4 6.6 8.8 11 13.2 15.4 17.6
10 12.2 14.4 16.6 18.8 21 23.2 25.4 27.6

Use subscript to assign value to valarray

<source lang="cpp">#include <iostream>

1. include <valarray>
2. include <cmath>

using namespace std; int main() {

 valarray<int> v(10);
 int i;
 for(i=0; i<10; i++) v[i] = i;
 cout << "Original contents: ";
 for(i=0; i<10; i++)
   cout << v[i] << " ";
 cout << endl;

}</source>

Original contents: 0 1 2 3 4 5 6 7 8 9