Sams Teach Yourself C++ in 21 Days

21: vInt[i] = i * 3;

22:

23: cout << “for_each()” << endl;

24: for_each(vInt.begin(), vInt.end(), DoPrint);

25: cout << endl;

26:

27: return 0;

28: }

for_each()

0 3 6 9 12

Note that all C++ standard algorithms are defined in <algorithm>, so it is

included on line 2 of the listing. Although most of the program should be easy

for you, one line, however, is worth reviewing. On line 24, the for_each()function is

called to go through each element in the vector vInt. For each element in the vector, it

invokes the DoPrintfunction object and passes the element to DoPrint.operator().

This results in the value of the element to be printed on the screen.

Mutating Sequence Operations

Mutating sequence operations perform operations that change the elements in a

sequence, including operations that fill or reorder collections. Listing 19.13 shows the

fill()algorithm.

LISTING19.13 A Mutating Sequence Algorithm

0: #include <iostream>

1: #include <vector>

2: #include <algorithm>

3: using namespace std;

4:

5: template<class T>

6: class Print

7: {

8: public:

9: void operator()(const T& t)

10: {

11: cout << t << “ “;

12: }

13: };

14:

15: int main()

16: {

17: Print<int> DoPrint;

18: vector<int> vInt(10);

OUTPUT

710 Day 19

LISTING19.12 continued

ANALYSIS