C++ Tutorial/valarray/valarray subscript indexer — различия между версиями
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Текущая версия на 13:31, 25 мая 2010
Assign value to valarray
<source lang="cpp">#include <iostream>
- include <valarray>
- 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. */
- include <iostream>
- 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>
- include <valarray>
- 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