/* 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 <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#include <numeric>
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
typename T::const_iterator pos;
std::cout << optcstr;
for (pos=coll.begin(); pos!=coll.end(); ++pos) {
std::cout << *pos << ' ';
}
std::cout << std::endl;
}
/* INSERT_ELEMENTS (collection, first, last)
* - fill values from first to last into the collection
* - NOTE: NO half-open range
*/
template <class T>
inline void INSERT_ELEMENTS (T& coll, int first, int last)
{
for (int i=first; i<=last; ++i) {
coll.insert(coll.end(),i);
}
}
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 (implicit type conversion)
operator double() {
return static_cast<double>(sum) / static_cast<double>(num);
}
};
int main()
{
vector<int> coll;
INSERT_ELEMENTS(coll,1,8);
// process and print mean value
double mv = for_each (coll.begin(), coll.end(), // range
MeanValue()); // operation
cout << "mean value: " << mv << endl;
}
/*
mean value: 4.5
*/
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