if_contains_type.h
Go to the documentation of this file.00001 /******************************************************************************* 00002 * 00003 * Copyright (c) 2008-2010 Michael Schulze <mschulze@ivs.cs.uni-magdeburg.de> 00004 * All rights reserved. 00005 * 00006 * Redistribution and use in source and binary forms, with or without 00007 * modification, are permitted provided that the following conditions 00008 * are met: 00009 * 00010 * * Redistributions of source code must retain the above copyright 00011 * notice, this list of conditions and the following disclaimer. 00012 * 00013 * * Redistributions in binary form must reproduce the above copyright 00014 * notice, this list of conditions and the following disclaimer in 00015 * the documentation and/or other materials provided with the 00016 * distribution. 00017 * 00018 * * Neither the name of the copyright holders nor the names of 00019 * contributors may be used to endorse or promote products derived 00020 * from this software without specific prior written permission. 00021 * 00022 * 00023 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS 00024 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 00025 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 00026 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 00027 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 00028 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 00029 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 00030 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 00031 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 00032 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 00033 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 00034 * 00035 * 00036 * $Id$ 00037 * 00038 ******************************************************************************/ 00039 #ifndef __if_contains_type_h__ 00040 #define __if_contains_type_h__ 00041 00042 #include "config/policies/EmptyPolicy.h" 00043 #include "config/type_traits/contains_type.h" 00044 00098 #define IF_CONTAINS_TYPE_(NAME) \ 00099 template < typename T, typename R = void> \ 00100 class if_contains_type_##NAME { \ 00101 CONTAINS_TYPE_(NAME); \ 00102 /* Generates Comile-Time Error if used in an ElsePolicy */ \ 00103 struct NAME; \ 00104 \ 00105 /* a compile time selector for the policies the first is */ \ 00106 /* the general purpose template and the second is a */ \ 00107 /* specialization that is used if the subtype exists */ \ 00108 template<bool U, typename ThenPolicy, \ 00109 typename ElsePolicy> \ 00110 struct PolicySelect_##NAME { \ 00111 static inline R do_it() { \ 00112 return ElsePolicy::template process<T, NAME, R>(); \ 00113 } \ 00114 }; \ 00115 \ 00116 template<typename ThenPolicy, typename ElsePolicy> \ 00117 struct PolicySelect_##NAME<true, ThenPolicy, ElsePolicy> { \ 00118 static inline R do_it() { \ 00119 return ThenPolicy::template process<T, \ 00120 typename T::NAME, \ 00121 R \ 00122 >(); \ 00123 } \ 00124 }; \ 00125 \ 00126 public: \ 00127 /* the value signalise if the subtype is defined or not */ \ 00128 static const bool value = contains_type_##NAME<T>::value; \ 00129 \ 00130 /* processes dependent on the value the respective template */ \ 00131 /* which leads to generating code */ \ 00132 template <typename ThenPolicy, \ 00133 typename ElsePolicy=EmptyPolicy > \ 00134 struct ThenElse { \ 00135 static inline R process() { \ 00136 return PolicySelect_##NAME< \ 00137 value, \ 00138 ThenPolicy, \ 00139 ElsePolicy \ 00140 >::do_it(); \ 00141 } \ 00142 }; \ 00143 } 00144 00145 #endif 00146