examples/manual/negator.cpp

/**************************************************************************
 *
 * negator.cpp - Example program for reversing the sense of predicate 
 *               function objects by using function adaptors and function
 *               objects.
 *
 * $Id: //stdlib/dev/examples/stdlib/manual/negator.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 <functional>   // for unary_function
#include <ios>          // for boolalpha
#include <iostream>     // for cout, endl

#include <examples.h>


// Create a new predicate from unary_function.
template <class Arg>
struct is_odd : public std::unary_function<Arg, bool>
{
    bool operator() (const Arg &arg1) const {
        return arg1 % 2 != 0;
    }
};


int main ()
{
    std::less<int> less_func;

    // Use not2 on less.
    std::cout << std::boolalpha
              << less_func (1, 4) << '\n'
              << less_func (4, 1) << '\n'
              << std::not2 (std::less<int>())(1, 4) << '\n'
              << std::not2 (std::less<int>())(4, 1) << '\n';

    // Create an instance of our predicate.
    is_odd<int> odd;

    // Use not1 on our user defined predicate.
    std::cout << odd (1) << '\n'
              << odd (4) << '\n'
              << std::not1 (odd)(1) << '\n'
              << std::not1 (odd)(4) << std::endl;

    return 0;
}