142 lines
3.2 KiB
C++
142 lines
3.2 KiB
C++
// Copyright Daniel Wallin 2006. Use, modification and distribution is
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// subject to the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_PARAMETER_CAST_060902_HPP
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# define BOOST_PARAMETER_CAST_060902_HPP
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# include <boost/detail/workaround.hpp>
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# if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
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# include <boost/type_traits/add_reference.hpp>
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# include <boost/type_traits/remove_const.hpp>
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# endif
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namespace boost { namespace parameter { namespace aux {
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struct use_default_tag {};
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# if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
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# define BOOST_PARAMETER_FUNCTION_CAST(value, predicate) value
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# else
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// Handles possible implicit casts. Used by preprocessor.hpp to
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// normalize user input.
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//
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// cast<void*>::execute() is identity
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// cast<void*(X)>::execute() is identity
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// cast<void(X)>::execute() casts to X
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//
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// preprocessor.hpp uses this like this:
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//
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// #define X(value, predicate)
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// cast<void predicate>::execute(value)
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//
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// X(something, *)
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// X(something, *(predicate))
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// X(something, (int))
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template <class T, class Args>
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struct cast;
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template <class Args>
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struct cast<void*, Args>
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{
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static use_default_tag execute(use_default_tag)
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{
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return use_default_tag();
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}
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static use_default_tag remove_const(use_default_tag)
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{
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return use_default_tag();
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}
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template <class U>
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static U& execute(U& value)
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{
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return value;
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}
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template <class U>
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static U& remove_const(U& x)
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{
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return x;
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}
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};
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#if BOOST_WORKAROUND(__SUNPRO_CC, BOOST_TESTED_AT(0x580))
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typedef void* voidstar;
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template <class T, class Args>
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struct cast<voidstar(T), Args>
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: cast<void*, Args>
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{
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};
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#else
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template <class T, class Args>
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struct cast<void*(T), Args>
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: cast<void*, Args>
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{
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};
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#endif
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// This is a hack used in cast<> to turn the user supplied type,
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// which may or may not be a placeholder expression into one, so
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// that it will be properly evaluated by mpl::apply.
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template <class T, class Dummy = mpl::_1>
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struct as_placeholder_expr
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{
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typedef T type;
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};
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template <class T, class Args>
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struct cast<void(T), Args>
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{
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typedef typename mpl::apply2<
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as_placeholder_expr<T>, Args, Args>::type type0;
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typedef typename boost::add_reference<
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typename boost::remove_const<type0>::type
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>::type reference;
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static use_default_tag execute(use_default_tag)
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{
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return use_default_tag();
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}
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static use_default_tag remove_const(use_default_tag)
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{
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return use_default_tag();
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}
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static type0 execute(type0 value)
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{
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return value;
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}
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template <class U>
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static reference remove_const(U const& x)
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{
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return const_cast<reference>(x);
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}
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};
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# define BOOST_PARAMETER_FUNCTION_CAST(value, predicate, args) \
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boost::parameter::aux::cast<void predicate, args>::remove_const( \
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boost::parameter::aux::cast<void predicate, args>::execute(value) \
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)
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# endif
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}}} // namespace boost::parameter::aux
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#endif // BOOST_PARAMETER_CAST_060902_HPP
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