The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference
by Nicolai M. Josuttis, Addison-Wesley, 1999
© Copyright Nicolai M. Josuttis 1999
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
// function object to process the mean value
class MeanValue {
private:
long num; // number of elements
long sum; // sum of all element values
public:
// constructor
MeanValue () : num(0), sum(0) {
}
// ``function call''
// - process one more element of the sequence
void operator() (int elem) {
num++; // increment count
sum += elem; // add value
}
// return mean value
double value () {
return static_cast<double>(sum) / static_cast<double>(num);
}
};
int main()
{
vector<int> coll;
// insert elments from 1 to 8
for (int i=1; i<=8; ++i) {
coll.push_back(i);
}
// process and print mean value
MeanValue mv = for_each (coll.begin(), coll.end(), // range
MeanValue()); // operation
cout << "mean value: " << mv.value() << endl;
}