stde/select.h

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/** @file
 *  @author Bram de Greve (bramz@users.sourceforge.net)
 *  @author Tom De Muer (tomdemuer@users.sourceforge.net)
 *
 *  *** BEGIN LICENSE INFORMATION ***
 *  
 *  The contents of this file are subject to the Common Public Attribution License 
 *  Version 1.0 (the "License"); you may not use this file except in compliance with 
 *  the License. You may obtain a copy of the License at 
 *  http://lass.sourceforge.net/cpal-license. The License is based on the 
 *  Mozilla Public License Version 1.1 but Sections 14 and 15 have been added to cover 
 *  use of software over a computer network and provide for limited attribution for 
 *  the Original Developer. In addition, Exhibit A has been modified to be consistent 
 *  with Exhibit B.
 *  
 *  Software distributed under the License is distributed on an "AS IS" basis, WITHOUT 
 *  WARRANTY OF ANY KIND, either express or implied. See the License for the specific 
 *  language governing rights and limitations under the License.
 *  
 *  The Original Code is LASS - Library of Assembled Shared Sources.
 *  
 *  The Initial Developer of the Original Code is Bram de Greve and Tom De Muer.
 *  The Original Developer is the Initial Developer.
 *  
 *  All portions of the code written by the Initial Developer are:
 *  Copyright (C) 2004-2007 the Initial Developer.
 *  All Rights Reserved.
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 *
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 *  GNU General Public License Version 2 or later (the GPL), in which case the 
 *  provisions of GPL are applicable instead of those above.  If you wish to allow use
 *  of your version of this file only under the terms of the GPL and not to allow 
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 *  *** END LICENSE INFORMATION ***
 */



/** @defgroup stde_select
 *  @brief functors to select element of std::pair or stde::triple
 *
 *  @code
 *  typedef std::map<std::string, int> map_type;
 *  map_type a;
 *  a["one"] = 1;
 *  a["two"] = 2;
 *  a["three"] = 3;
 *  std::transform(a.begin(), a.end(), 
 *      std::ostream_iterator<map_type::key_type>(std::cout, " "),
 *      stde::select_1st<map_type::value_type>());
 *  @endcode
 */


#ifndef LASS_GUARDIAN_OF_INCLUSION_STDE_SELECT_H
#define LASS_GUARDIAN_OF_INCLUSION_STDE_SELECT_H

#include "stde_common.h"
#include "../util/call_traits.h"

namespace lass
{
namespace stde
{

/** selects first element of std::pair or stde::triple and applies supplied operator on it
 *  @ingroup stde_select
 */
template <typename Pair>
struct select_1st: public std::unary_function<Pair, typename Pair::first_type>
{
    typename util::CallTraits<typename Pair::first_type>::TParam 
    operator()(typename util::CallTraits<Pair>::TParam iArgument) 
    { 
        return iArgument.first; 
    }
};



/** selects second element of std::pair or stde::triple and applies supplied operator on it
 *  @ingroup stde_select
 */
template <typename Pair>
struct select_2nd: public std::unary_function<Pair, typename Pair::second_type>
{
    typename util::CallTraits<typename Pair::second_type>::TParam 
    operator()(typename util::CallTraits<Pair>::TParam iArgument) 
    { 
        return iArgument.second; 
    }
};



/** selects second element of std::pair or stde::triple and applies supplied operator on it
 *  @ingroup stde_select
 */
template <typename Triple>
struct select_3rd: public std::unary_function<Triple, typename Triple::third_type>
{
    typename util::CallTraits<typename Triple::third_type>::TParam 
    operator()(typename util::CallTraits<Triple>::TParam iArgument) 
    { 
        return iArgument.third; 
    }
};

}

}

#endif

// EOF