vmap/libs/generic/constant.h

/*
   Copyright (C) 2001-2006, William Joseph.
   All Rights Reserved.

   This file is part of GtkRadiant.

   GtkRadiant is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   GtkRadiant is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with GtkRadiant; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#if !defined( INCLUDED_GENERIC_CONSTANT_H )
#define INCLUDED_GENERIC_CONSTANT_H

/// \file
/// \brief Language extensions for constants that are guaranteed to be evaluated at compile-time.

/// \brief A compile-time-constant as a type.
template<typename Type>
struct ConstantWrapper
{
	typedef typename Type::Value Value;
	operator Value() const
	{
		return Type::evaluate();
	}
};
template<typename TextOutputStreamType,  typename Type>
inline TextOutputStreamType& ostream_write( TextOutputStreamType& ostream, const ConstantWrapper<Type>& c ){
	return ostream_write( ostream, typename Type::Value( c ) );
}

#define TYPE_CONSTANT( name, value, type ) struct name ## _CONSTANT_ { typedef type Value; static Value evaluate() { return value; } }; typedef ConstantWrapper<name ## _CONSTANT_> name
#define STRING_CONSTANT( name, value ) TYPE_CONSTANT ( name, value, const char* )
#define INTEGER_CONSTANT( name, value ) TYPE_CONSTANT ( name, value, int )
#define UINT_CONSTANT( name, value ) TYPE_CONSTANT ( name, value, unsigned int )

STRING_CONSTANT( EmptyString, "" );

#endif