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

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C++ Tutorial » STL Introduction » predicate 
14.9.8.Convenience function for the compose_f_gx_hy adapter
/* 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 <algorithm>
#include <functional>
#include <string>
#include <cctype>

using namespace std;


#include <functional>

/* class for the compose_f_gx_hy adapter
 */
template <class OP1, class OP2, class OP3>
class compose_f_gx_hy_t
 public std::binary_function<typename OP2::argument_type,
                               typename OP3::argument_type,
                               typename OP1::result_type>
{
  private:
    OP1 op1;    // process: op1(op2(x),op3(y))
    OP2 op2;
    OP3 op3;
  public:
    // constructor
    compose_f_gx_hy_t (const OP1& o1, const OP2& o2, const OP3& o3)
     : op1(o1), op2(o2), op3(o3) {
    }

    // function call
    typename OP1::result_type
    operator()(const typename OP2::argument_type& x,
               const typename OP3::argument_type& yconst {
        return op1(op2(x),op3(y));
    }
};

/* convenience function for the compose_f_gx_hy adapter
 */
template <class OP1, class OP2, class OP3>
inline compose_f_gx_hy_t<OP1,OP2,OP3>
compose_f_gx_hy (const OP1& o1, const OP2& o2, const OP3& o3) {
    return compose_f_gx_hy_t<OP1,OP2,OP3>(o1,o2,o3);
}


int main()
{
    string s("Internationalization");
    string sub("Nation");

    // search substring case insensitive
    string::iterator pos;
    pos = search (s.begin(),s.end(),           // string to search in
                  sub.begin(),sub.end(),       // substring to search
                  compose_f_gx_hy(equal_to<int>()// compar. criterion
                                  ptr_fun(::toupper),
                                  ptr_fun(::toupper)));

    if (pos != s.end()) {
        cout << "\"" << sub << "\" is part of \"" << s << "\""
             << endl;
    }
}
"Nation" is part of "Internationalization"
14.9.predicate
14.9.1.Create your own unary function
14.9.2.use generic function as predicate
14.9.3.Function object to process the mean value
14.9.4.Illustrating the use of an adaptor for pointers to functions
14.9.5.Use predicate, which returns whether an integer is a prime number, with a list
14.9.6.Convenience function for the compose_f_gx adapter
14.9.7.Convenience function for the compose_f_gx_hx adapter
14.9.8.Convenience function for the compose_f_gx_hy adapter
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