Milena (Olena)  User documentation 2.0a Id
zero.hh
00001 // Copyright (C) 2007, 2008, 2009, 2011 EPITA Research and Development
00002 // Laboratory (LRDE)
00003 //
00004 // This file is part of Olena.
00005 //
00006 // Olena is free software: you can redistribute it and/or modify it under
00007 // the terms of the GNU General Public License as published by the Free
00008 // Software Foundation, version 2 of the License.
00009 //
00010 // Olena is distributed in the hope that it will be useful,
00011 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00012 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013 // General Public License for more details.
00014 //
00015 // You should have received a copy of the GNU General Public License
00016 // along with Olena.  If not, see <http://www.gnu.org/licenses/>.
00017 //
00018 // As a special exception, you may use this file as part of a free
00019 // software project without restriction.  Specifically, if other files
00020 // instantiate templates or use macros or inline functions from this
00021 // file, or you compile this file and link it with other files to produce
00022 // an executable, this file does not by itself cause the resulting
00023 // executable to be covered by the GNU General Public License.  This
00024 // exception does not however invalidate any other reasons why the
00025 // executable file might be covered by the GNU General Public License.
00026 
00027 #ifndef MLN_LITERAL_ZERO_HH
00028 # define MLN_LITERAL_ZERO_HH
00029 
00035 
00036 # include <mln/core/concept/literal.hh>
00037 # include <mln/metal/converts_to.hh>
00038 
00039 
00040 namespace mln
00041 {
00042 
00043   namespace literal
00044   {
00045 
00047     struct zero_t : public Literal<zero_t>
00048     {
00049       // This default constructor is needed for compilation with gcc
00050       // 4.6.0, gcc 4.6.1 and Clang.
00051       zero_t();
00052 
00053       // FIXME: (for the record) Add "friend class Literal<zero_t>;" and a protected ctor.
00054 
00055       template <typename T>
00056       operator const T () const;
00057     };
00058 
00060     extern const zero_t zero;
00061 
00062 # ifndef MLN_INCLUDE_ONLY
00063 
00064     inline
00065     zero_t::zero_t()
00066     {
00067     }
00068 
00069     template <typename T>
00070     inline
00071     zero_t::operator const T () const
00072     {
00073       mlc_converts_to(int, T)::check();
00074       return 0;
00075     }
00076 
00077 #  ifndef MLN_WO_GLOBAL_VARS
00078 
00079     const zero_t zero;
00080 
00081 #  endif // !MLN_WO_GLOBAL_VARS
00082 
00083 # endif // ! MLN_INCLUDE_ONLY
00084 
00085   } // end of namespace mln::literal
00086 
00087 } // end of namespace mln
00088 
00089 
00090 #endif // ! MLN_LITERAL_ZERO_HH
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