examples/manual/funct_ob.cpp

/**************************************************************************
 *
 * funct_ob.cpp - Example program for function objects.
 *
 * $Id: //stdlib/dev/examples/stdlib/manual/funct_ob.cpp#12 $
 *
 ***************************************************************************
 *
 * Copyright (c) 1994-2005 Quovadx,  Inc., acting through its  Rogue Wave
 * Software division. Licensed under the Apache License, Version 2.0 (the
 * "License");  you may  not use this file except  in compliance with the
 * License.    You    may   obtain   a   copy   of    the   License    at
 * http://www.apache.org/licenses/LICENSE-2.0.    Unless   required    by
 * applicable law  or agreed to  in writing,  software  distributed under
 * the License is distributed on an "AS IS" BASIS,  WITHOUT WARRANTIES OR
 * CONDITIONS OF  ANY KIND, either  express or implied.  See  the License
 * for the specific language governing permissions  and limitations under
 * the License.
 * 
 **************************************************************************/

#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;
}