transform

#include <iostream>
#include <algorithm>
#include <vector>
#include <functional>
 
using namespace std;
 
// the function object multiplies an element by a Factor
template <class Type>
class MultValue
{
  private:
    Type Factor; // the value to multiply by
  public:
    // constructor initializes the value to multiply by
    MultValue(const Type& _Val) : Factor(_Val) {    } 
 
    // the function call for the element to be multiplied
    int operator()(Type& elem) const
      {return (elem * Factor);}
};
 
int main()
{
  vector <int> vec1, vec2(7), vec3(7);
  vector <int>::iterator Iter1, Iter2, Iter3;
 
  // constructing vector vec1
  for (int i = -4; i <= 2; i++)
    vec1.push_back(i);
  cout <<"Original vector vec1 data: ";
  for (Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)
    cout <<*Iter1<<" ";
  cout <<endl;
 
  // modifying the vector vec1 in place
  transform(vec1.begin(), vec1.end(), vec1.begin(),
                                      MultValue<int>(2));
  cout <<"\nThe elements of the vector vec1 multiplied by 2 in place gives:"
         "\nvec1mod data: ";
  for (Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)
    cout <<*Iter1<<" ";
  cout <<endl;
 
  // using transform() to multiply each element by a factor of 5
  transform(vec1.begin(), vec1.end(), vec2.begin(),
                                      MultValue<int>(5));
  cout <<"\nMultiplying the elements of the vector vec1mod"
         "\nby the factor 5 & copying to vec2 gives:\nvec2 data: ";
  for (Iter2 = vec2.begin(); Iter2 != vec2.end(); Iter2++)
    cout <<*Iter2<<" ";
  cout <<endl;
 
  // the second version of transform used to multiply the elements of the vectors vec1mod & vec2 pairwise
  transform(vec1.begin(), vec1.end(), vec2.begin(), vec3.begin(), 
                                                    multiplies<int>());
  cout <<"\nMultiplying elements of the vectors vec1mod and" 
         "vec2 pairwise gives:\nvec3 data: ";
  for (Iter3 = vec3.begin(); Iter3 != vec3.end(); Iter3++)
    cout <<*Iter3<<" ";
  cout <<endl;
 
  return 0;
}