63e88f80
 Hu Chunming
提交三方库
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// (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
// (C) Copyright 2003-2007 Jonathan Turkanis
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
// See http://www.boost.org/libs/iostreams for documentation.
// Contains the metafunction select, which mimics the effect of a chain of
// nested mpl if_'s.
//
// -----------------------------------------------------------------------------
//
// Usage:
//
// typedef typename select<
// case1, type1,
// case2, type2,
// ...
// true_, typen
// >::type selection;
//
// Here case1, case2, ... are models of MPL::IntegralConstant with value type
// bool, and n <= 12.
#ifndef BOOST_IOSTREAMS_SELECT_HPP_INCLUDED
#define BOOST_IOSTREAMS_SELECT_HPP_INCLUDED
#if defined(_MSC_VER)
# pragma once
#endif
#include <boost/type_traits/is_base_and_derived.hpp>
#include <boost/mpl/eval_if.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/mpl/if.hpp>
#include <boost/mpl/void.hpp>
namespace boost { namespace iostreams {
typedef mpl::true_ else_;
template< typename Case1 = mpl::true_,
typename Type1 = mpl::void_,
typename Case2 = mpl::true_,
typename Type2 = mpl::void_,
typename Case3 = mpl::true_,
typename Type3 = mpl::void_,
typename Case4 = mpl::true_,
typename Type4 = mpl::void_,
typename Case5 = mpl::true_,
typename Type5 = mpl::void_,
typename Case6 = mpl::true_,
typename Type6 = mpl::void_,
typename Case7 = mpl::true_,
typename Type7 = mpl::void_,
typename Case8 = mpl::true_,
typename Type8 = mpl::void_,
typename Case9 = mpl::true_,
typename Type9 = mpl::void_,
typename Case10 = mpl::true_,
typename Type10 = mpl::void_,
typename Case11 = mpl::true_,
typename Type11 = mpl::void_,
typename Case12 = mpl::true_,
typename Type12 = mpl::void_ >
struct select {
typedef typename
mpl::eval_if<
Case1, mpl::identity<Type1>, mpl::eval_if<
Case2, mpl::identity<Type2>, mpl::eval_if<
Case3, mpl::identity<Type3>, mpl::eval_if<
Case4, mpl::identity<Type4>, mpl::eval_if<
Case5, mpl::identity<Type5>, mpl::eval_if<
Case6, mpl::identity<Type6>, mpl::eval_if<
Case7, mpl::identity<Type7>, mpl::eval_if<
Case8, mpl::identity<Type8>, mpl::eval_if<
Case9, mpl::identity<Type9>, mpl::eval_if<
Case10, mpl::identity<Type10>, mpl::eval_if<
Case11, mpl::identity<Type11>, mpl::if_<
Case12, Type12, mpl::void_ > > > > > > > > > > >
>::type type;
};
} } // End namespaces iostreams, boost.
#endif // #ifndef BOOST_IOSTREAMS_SELECT_HPP_INCLUDED
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