funct_ob.cpp

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#include <algorithm>
#include <deque>
#include <functional>
#include <iostream>
#include <iterator>
#include <vector>
 
 
// Create a new function object from unary_function.
template <class Arg, class Result>
struct factorial: public std::unary_function<Arg, Result>
{
    Result operator() (const Arg &arg) {
        Result a = 1;
        for (Arg i = 2; i <= arg; i++)
            a *= i;
        return a;
    }
};
 
 
int main ()
{
    // Typedefs for convenience.
    typedef std::deque<int, std::allocator<int> >    Deque;
    typedef std::vector<long, std::allocator<long> > Vector;
 
    // Initialize a deque with an array of integers.
    Deque::value_type arr[] = { 1, 2, 3, 4, 5, 6, 7 };
    Deque d (arr, arr + sizeof arr / sizeof *arr);
 
    // Create an empty vector to store the factorials.
    Vector v;
 
    // Transform the numbers in the deque to their factorials
    // and store in the vector.
    std::transform (d.begin (), d.end (), 
                    std::back_inserter (v),
                    factorial<Deque::value_type, Vector::value_type>());
 
    // Create an iterator to output deque elements.
    std::ostream_iterator<Deque::value_type, 
                          char, 
                          std::char_traits<char> > outd (std::cout, " ");
 
    // Print the results.
    std::cout << "The following numbers: \n     ";
    std::copy (d.begin (), d.end (), outd);
 
    // Create an iterator to output vector elements.
    std::ostream_iterator<Vector::value_type, 
                          char, 
                          std::char_traits<char> > outv (std::cout, " ");
 
    std::cout << std::endl;
    std::cout << "\nHave the factorials: \n     ";
    std::copy (v.begin (), v.end (), outv);
    std::cout << std::endl;
 
    return 0;
}