simple_visitor_cast.hh

00001 /* vim: set sw=4 sts=4 et foldmethod=syntax : */
00002 
00003 /*
00004  * Copyright (c) 2008 Ciaran McCreesh
00005  *
00006  * This file is part of the Paludis package manager. Paludis is free software;
00007  * you can redistribute it and/or modify it under the terms of the GNU General
00008  * Public License version 2, as published by the Free Software Foundation.
00009  *
00010  * Paludis is distributed in the hope that it will be useful, but WITHOUT ANY
00011  * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
00012  * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
00013  * details.
00014  *
00015  * You should have received a copy of the GNU General Public License along with
00016  * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
00017  * Place, Suite 330, Boston, MA  02111-1307  USA
00018  */
00019 
00020 #ifndef PALUDIS_GUARD_PALUDIS_UTIL_SIMPLE_VISITOR_CAST_HH
00021 #define PALUDIS_GUARD_PALUDIS_UTIL_SIMPLE_VISITOR_CAST_HH 1
00022 
00023 #include <paludis/util/simple_visitor_cast-fwd.hh>
00024 #include <paludis/util/simple_visitor.hh>
00025 #include <tr1/type_traits>
00026 
00027 namespace paludis
00028 {
00029     template <typename To_, typename From_>
00030     struct SimpleVisitorCaster
00031     {
00032         To_ * visit(const To_ & t)
00033         {
00034             return &t;
00035         }
00036 
00037         To_ * visit(const From_ &)
00038         {
00039             return 0;
00040         }
00041     };
00042 
00043     template <typename To_, typename From_>
00044     To_ * simple_visitor_cast(const From_ & from)
00045     {
00046         SimpleVisitorCaster<To_, From_> q;
00047         return from.template accept_returning<To_ *>(q);
00048     }
00049 }
00050 
00051 #endif

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