88 lines
3.2 KiB
C++
88 lines
3.2 KiB
C++
// Copyright Daniel Wallin 2006.
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// Copyright Cromwell D. Enage 2017.
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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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#ifndef BOOST_PARAMETER_TEMPLATE_KEYWORD_HPP
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#define BOOST_PARAMETER_TEMPLATE_KEYWORD_HPP
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#include <boost/parameter/aux_/template_keyword.hpp>
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#include <boost/parameter/config.hpp>
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#if defined(BOOST_PARAMETER_CAN_USE_MP11)
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#include <boost/mp11/integral.hpp>
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#include <boost/mp11/utility.hpp>
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#include <type_traits>
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#else
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#include <boost/mpl/bool.hpp>
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#include <boost/mpl/if.hpp>
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#include <boost/mpl/eval_if.hpp>
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#include <boost/mpl/identity.hpp>
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#include <boost/type_traits/add_lvalue_reference.hpp>
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#include <boost/type_traits/is_function.hpp>
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#include <boost/type_traits/is_array.hpp>
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#endif
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namespace boost { namespace parameter {
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template <typename Tag, typename T>
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struct template_keyword : ::boost::parameter::aux::template_keyword_base
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{
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typedef Tag key_type;
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typedef T value_type;
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// reference is needed for two reasons:
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//
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// 1. It is used in the body of arg_list<...>
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//
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// 2. It is the result of binding<...>, which we mistakenly told
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// people to use instead of value_type<...> to access named
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// template parameters
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//
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// It used to be that reference == value_type, but that broke when
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// the argument was a function or array type, because various
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// arg_list functions return reference.
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//
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// Simply making reference == value_type& would break all the
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// legacy code that uses binding<...> to access named template
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// parameters. -- David Abrahams
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#if defined(BOOST_PARAMETER_CAN_USE_MP11)
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using reference = typename ::boost::mp11::mp_eval_if<
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::boost::mp11::mp_if<
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::std::is_function<value_type>
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, ::boost::mp11::mp_true
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, ::std::is_array<value_type>
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>
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, ::std::add_lvalue_reference<value_type>
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, ::boost::mp11::mp_identity
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, value_type
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>::type;
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#else
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typedef typename ::boost::mpl::eval_if<
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typename ::boost::mpl::if_<
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::boost::is_function<value_type>
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, ::boost::mpl::true_
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, ::boost::is_array<value_type>
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>::type
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, ::boost::add_lvalue_reference<value_type>
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, ::boost::mpl::identity<value_type>
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>::type reference;
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#endif // BOOST_PARAMETER_CAN_USE_MP11
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};
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}} // namespace boost::parameter
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#define BOOST_PARAMETER_TEMPLATE_KEYWORD(name) \
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namespace tag \
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{ \
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struct name; \
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} \
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template <typename T> \
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struct name : ::boost::parameter::template_keyword<tag::name,T> \
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{ \
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};
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/**/
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#endif // include guard
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