Convenience function for the compose_f_gx adapter : predicate « STL Introduction « C++ Tutorial

1. C++ Tutorial
2. STL Introduction
3. predicate

/* 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>
#include <functional>
#include <iterator>
using namespace std;

/* 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;
}




/* class for the compose_f_gx adapter
 */
template <class OP1, class OP2>
class compose_f_gx_t
 : public std::unary_function<typename OP2::argument_type,
                              typename OP1::result_type>
{
  private:
    OP1 op1;    // process: op1(op2(x))
    OP2 op2;
  public:
    // constructor
    compose_f_gx_t(const OP1& o1, const OP2& o2)
     : op1(o1), op2(o2) {
    }

    // function call
    typename OP1::result_type
    operator()(const typename OP2::argument_type& x) const {
        return op1(op2(x));
    }
};

/* convenience function for the compose_f_gx adapter
 */
template <class OP1, class OP2>
inline compose_f_gx_t<OP1,OP2>
compose_f_gx (const OP1& o1, const OP2& o2) {
    return compose_f_gx_t<OP1,OP2>(o1,o2);
}


int main()
{
    vector<int> coll;

    // insert elements from 1 to 9
    for (int i=1; i<=9; ++i) {
        coll.push_back(i);
    }
    PRINT_ELEMENTS(coll);

    // for each element add 10 and multiply by 5
    transform (coll.begin(),coll.end(),
               ostream_iterator<int>(cout," "),
               compose_f_gx(bind2nd(multiplies<int>(),5),
                            bind2nd(plus<int>(),10)));
    cout << endl;
}

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