/* 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 <vector>#include <algorithm>using namespace std;// function object to process the mean valueclass 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;}