59 lines
2.2 KiB
C++
59 lines
2.2 KiB
C++
/* Copyright 2006-2008 Joaquin M Lopez Munoz.
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* See http://www.boost.org/libs/flyweight for library home page.
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*/
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#ifndef BOOST_FLYWEIGHT_DETAIL_NOT_PLACEHOLDER_EXPR_HPP
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#define BOOST_FLYWEIGHT_DETAIL_NOT_PLACEHOLDER_EXPR_HPP
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#if defined(_MSC_VER)&&(_MSC_VER>=1200)
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#pragma once
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#endif
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/* BOOST_FLYWEIGHT_NOT_A_PLACEHOLDER_EXPRESSION can be inserted at the end
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* of a class template parameter declaration:
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* template<
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* typename X0,...,typename Xn
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* BOOST_FLYWEIGHT_NOT_A_PLACEHOLDER_EXPRESSION
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* >
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* struct foo...
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* to prevent instantiations from being treated as MPL placeholder
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* expressions in the presence of placeholder arguments; this is useful
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* to avoid masking of a metafunction class nested ::apply during
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* MPL invocation.
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*/
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#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
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#include <boost/detail/workaround.hpp>
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#if BOOST_WORKAROUND(__GNUC__, <4)||\
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BOOST_WORKAROUND(__GNUC__,==4)&&(__GNUC_MINOR__<2)
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/* The default trick on which the macro is based, namely adding a int=0
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* defaulted template parameter, does not work in GCC prior to 4.2 due to
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* an unfortunate compiler non-standard extension, as explained in
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* http://lists.boost.org/boost-users/2007/07/29866.php
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* We resort to an uglier technique, adding defaulted template parameters
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* so as to exceed BOOST_MPL_LIMIT_METAFUNCTION_ARITY.
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*/
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#include <boost/mpl/limits/arity.hpp>
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#include <boost/preprocessor/facilities/intercept.hpp>
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#include <boost/preprocessor/repetition/enum_trailing_params.hpp>
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#define BOOST_FLYWEIGHT_NOT_A_PLACEHOLDER_EXPRESSION \
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BOOST_PP_ENUM_TRAILING_PARAMS( \
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BOOST_MPL_LIMIT_METAFUNCTION_ARITY,typename=int BOOST_PP_INTERCEPT)
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#define BOOST_FLYWEIGHT_NOT_A_PLACEHOLDER_EXPRESSION_DEF \
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BOOST_PP_ENUM_TRAILING_PARAMS( \
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BOOST_MPL_LIMIT_METAFUNCTION_ARITY,typename BOOST_PP_INTERCEPT)
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#else
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#define BOOST_FLYWEIGHT_NOT_A_PLACEHOLDER_EXPRESSION ,int=0
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#define BOOST_FLYWEIGHT_NOT_A_PLACEHOLDER_EXPRESSION_DEF ,int
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#endif
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#endif
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