examples/manual/binders.cpp

/**************************************************************************
 *
 * binders.cpp - Example program for binder1st & binder2nd.
 *
 * $Id: //stdlib/dev/examples/stdlib/manual/binders.cpp#13 $
 *
 ***************************************************************************
 *
 * 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>   // for find_if
#include <functional>  // for equal_to, bind1st, bind2nd
#include <iostream>    // for cout, endl
#include <vector>      // for vector

#include <examples.h>


int main ()
{
    typedef std::vector<int, std::allocator<int> > Vector;
    typedef std::equal_to<Vector::value_type>      equal_to;

    const Vector::value_type arr [] = { 1, 2, 3, 4 };

    // Set up a vector.
    Vector v1 (arr + 0, arr + sizeof arr / sizeof *arr);

    // Create an 'equal to 3' unary predicate by binding 3 to
    // the equal_to binary predicate.
    std::binder1st<equal_to> equal_to_3 = std::bind1st (equal_to (), 3);

    // Now use this new predicate in a call to find_if.
    Vector::iterator it1 = std::find_if (v1.begin (), v1.end (),
                                         equal_to_3);

    // Even better, construct the new predicate on the fly.
    Vector::iterator it2 =
        std::find_if (v1.begin (), v1.end (),
                      std::bind1st (equal_to (), 3)); 

    // And now the same thing using bind2nd.
    // Same result since equal_to is commutative.
    Vector::iterator it3 =
        std::find_if (v1.begin (), v1.end (),
                      std::bind2nd (equal_to (), 3)); 

    // Output results.
    std::cout << *it1 << " " << *it2 << " " << *it3 << std::endl;

    return 0;
}