pair_comparator.hh

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00001 /*
00002    The lestes compiler suite
00003    Copyright (C) 2002, 2003, 2004, 2005 Miroslav Tichy
00004    Copyright (C) 2002, 2003, 2004, 2005 Petr Zika
00005    Copyright (C) 2002, 2003, 2004, 2005 Vojtech Hala
00006    Copyright (C) 2002, 2003, 2004, 2005 Jiri Kosina
00007    Copyright (C) 2002, 2003, 2004, 2005 Pavel Sanda
00008    Copyright (C) 2002, 2003, 2004, 2005 Jan Zouhar
00009    Copyright (C) 2002, 2003, 2004, 2005 Rudolf Thomas
00010 
00011    This program is free software; you can redistribute it and/or modify
00012    it under the terms of the GNU General Public License as published by
00013    the Free Software Foundation; version 2 of the License.
00014 
00015    This program is distributed in the hope that it will be useful,
00016    but WITHOUT ANY WARRANTY; without even the implied warranty of
00017    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00018    GNU General Public License for more details.
00019 
00020    See the full text of the GNU General Public License version 2, and
00021    the limitations in the file doc/LICENSE.
00022 
00023    By accepting the license the licensee waives any and all claims
00024    against the copyright holder(s) related in whole or in part to the
00025    work, its use, and/or the inability to use it.
00026  
00027  */
00028 #ifndef lestes__std___pair_comparator_hh___included
00029 #define lestes__std___pair_comparator_hh___included
00030 
00031 #include <lestes/common.hh>
00032 #include <functional>
00033 
00034 /*! \file
00035   \brief lexicographic ordering on pairs
00036   \author TMA
00037 
00038   This file provvides one template class ::lestes::std::pair_comparator, which
00039   performs lexicographic ordering.
00040  */
00041 
00042 package(lestes);
00043 package(std);
00044 
00045 #ifdef _MSC_VER
00046 #define NO_TEMPLATE_TEMPLATE_PARAMETERS 1
00047 #else
00048 #define NO_TEMPLATE_TEMPLATE_PARAMETERS 0
00049 #endif
00050 
00051 #if NO_TEMPLATE_TEMPLATE_PARAMETERS
00052 template < typename T >
00053 #else
00054 template < typename T, template < typename U > class ComparatorFirst = ::std::less, template < typename U > class ComparatorSecond = ComparatorFirst >
00055 #endif
00056 class pair_comparator {
00057 public:
00058 
00059 #if NO_TEMPLATE_TEMPLATE_PARAMETERS
00060         typedef ::std::less < typename T::pointee_type::first_type > comparator_first;
00061         typedef ::std::less < typename T::pointee_type::second_type > comparator_second;
00062 #else
00063         typedef ComparatorFirst < typename T::pointee_type::first_type > comparator_first;
00064         typedef ComparatorSecond < typename T::pointee_type::second_type > comparator_second;
00065 #endif
00066 
00067         /*!
00068          * \brief compares lexicographically a pair
00069          *
00070          * The inner workings determine the ordering by examining first the
00071          * first part of the pair.  If the first pair's first element is
00072          * strictly less (where less is the relation of \p ComparatorFirst)
00073          * than the second's, the whole first pair is less (the relation
00074          * imposed by this comparator) than the second. If however the second's
00075          * first is less than the first's, the first pair is not less than
00076          * second.  In the remaining case, i.e. neither first's first nor
00077          * second's first is less than the other, the relation on the pair is
00078          * determined solely by \p ComparatorSecond on the seconds of both
00079          * pairs.
00080          */
00081          bool operator() (const T & a, const T & b) const
00082          {
00083                  comparator_first ftc;
00084                  bool ab = ftc(a->first, b->first);
00085                  if (ab)
00086                          return true;
00087                  bool ba = ftc(b->first, a->first);
00088                  if (ba)
00089                          return false;
00090                  comparator_second stc;
00091                  return stc(a->second, b->second);
00092          }
00093 };
00094 
00095 end_package(std);
00096 end_package(lestes);
00097 
00098 #endif  // lestes__std___pair_comparator_hh___included
00099 /* vim: set ft=lestes : */

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