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87 lines
3.0 KiB
87 lines
3.0 KiB
3 years ago
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// (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
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// (C) Copyright 2003-2007 Jonathan Turkanis
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// Distributed under 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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// See http://www.boost.org/libs/iostreams for documentation.
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// Contains the metafunction select, which mimics the effect of a chain of
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// nested mpl if_'s.
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//
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// -----------------------------------------------------------------------------
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//
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// Usage:
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//
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// typedef typename select<
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// case1, type1,
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// case2, type2,
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// ...
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// true_, typen
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// >::type selection;
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//
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// Here case1, case2, ... are models of MPL::IntegralConstant with value type
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// bool, and n <= 12.
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#ifndef BOOST_IOSTREAMS_SELECT_HPP_INCLUDED
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#define BOOST_IOSTREAMS_SELECT_HPP_INCLUDED
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#if defined(_MSC_VER)
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# pragma once
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#endif
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#include <boost/type_traits/is_base_and_derived.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/mpl/if.hpp>
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#include <boost/mpl/void.hpp>
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namespace boost { namespace iostreams {
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typedef mpl::true_ else_;
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template< typename Case1 = mpl::true_,
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typename Type1 = mpl::void_,
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typename Case2 = mpl::true_,
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typename Type2 = mpl::void_,
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typename Case3 = mpl::true_,
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typename Type3 = mpl::void_,
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typename Case4 = mpl::true_,
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typename Type4 = mpl::void_,
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typename Case5 = mpl::true_,
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typename Type5 = mpl::void_,
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typename Case6 = mpl::true_,
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typename Type6 = mpl::void_,
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typename Case7 = mpl::true_,
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typename Type7 = mpl::void_,
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typename Case8 = mpl::true_,
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typename Type8 = mpl::void_,
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typename Case9 = mpl::true_,
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typename Type9 = mpl::void_,
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typename Case10 = mpl::true_,
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typename Type10 = mpl::void_,
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typename Case11 = mpl::true_,
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typename Type11 = mpl::void_,
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typename Case12 = mpl::true_,
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typename Type12 = mpl::void_ >
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struct select {
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typedef typename
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mpl::eval_if<
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Case1, mpl::identity<Type1>, mpl::eval_if<
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Case2, mpl::identity<Type2>, mpl::eval_if<
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Case3, mpl::identity<Type3>, mpl::eval_if<
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Case4, mpl::identity<Type4>, mpl::eval_if<
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Case5, mpl::identity<Type5>, mpl::eval_if<
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Case6, mpl::identity<Type6>, mpl::eval_if<
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Case7, mpl::identity<Type7>, mpl::eval_if<
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Case8, mpl::identity<Type8>, mpl::eval_if<
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Case9, mpl::identity<Type9>, mpl::eval_if<
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Case10, mpl::identity<Type10>, mpl::eval_if<
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Case11, mpl::identity<Type11>, mpl::if_<
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Case12, Type12, mpl::void_ > > > > > > > > > > >
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>::type type;
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};
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} } // End namespaces iostreams, boost.
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#endif // #ifndef BOOST_IOSTREAMS_SELECT_HPP_INCLUDED
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