ceph/src/boost/libs/iostreams/include/boost/iostreams/detail/select.hpp

   1 // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
   2 // (C) Copyright 2003-2007 Jonathan Turkanis
   3 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   4 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
   5
   6 // See http://www.boost.org/libs/iostreams for documentation.
   7
   8 // Contains the metafunction select, which mimics the effect of a chain of
   9 // nested mpl if_'s.
  10 //
  11 // -----------------------------------------------------------------------------
  12 //
  13 // Usage:
  14 //
  15 // typedef typename select<
  16 //                      case1,  type1,
  17 //                      case2,  type2,
  18 //                      ...
  19 //                      true_,  typen
  20 //                  >::type selection;
  21 //
  22 // Here case1, case2, ... are models of MPL::IntegralConstant with value type
  23 // bool, and n <= 12.
  24
  25 #ifndef BOOST_IOSTREAMS_SELECT_HPP_INCLUDED
  26 #define BOOST_IOSTREAMS_SELECT_HPP_INCLUDED
  27
  28 #if defined(_MSC_VER)
  29 # pragma once
  30 #endif
  31
  32 #include <boost/type_traits/is_base_and_derived.hpp>
  33 #include <boost/mpl/eval_if.hpp>
  34 #include <boost/mpl/identity.hpp>
  35 #include <boost/mpl/if.hpp>
  36 #include <boost/mpl/void.hpp>
  37
  38 namespace boost { namespace iostreams {
  39
  40 typedef mpl::true_ else_;
  41
  42 template< typename Case1 = mpl::true_,
  43           typename Type1 = mpl::void_,
  44           typename Case2 = mpl::true_,
  45           typename Type2 = mpl::void_,
  46           typename Case3 = mpl::true_,
  47           typename Type3 = mpl::void_,
  48           typename Case4 = mpl::true_,
  49           typename Type4 = mpl::void_,
  50           typename Case5 = mpl::true_,
  51           typename Type5 = mpl::void_,
  52           typename Case6 = mpl::true_,
  53           typename Type6 = mpl::void_,
  54           typename Case7 = mpl::true_,
  55           typename Type7 = mpl::void_,
  56           typename Case8 = mpl::true_,
  57           typename Type8 = mpl::void_,
  58           typename Case9 = mpl::true_,
  59           typename Type9 = mpl::void_,
  60           typename Case10 = mpl::true_,
  61           typename Type10 = mpl::void_,
  62           typename Case11 = mpl::true_,
  63           typename Type11 = mpl::void_,
  64           typename Case12 = mpl::true_,
  65           typename Type12 = mpl::void_ >
  66 struct select {
  67     typedef typename
  68             mpl::eval_if<
  69                 Case1, mpl::identity<Type1>, mpl::eval_if<
  70                 Case2, mpl::identity<Type2>, mpl::eval_if<
  71                 Case3, mpl::identity<Type3>, mpl::eval_if<
  72                 Case4, mpl::identity<Type4>, mpl::eval_if<
  73                 Case5, mpl::identity<Type5>, mpl::eval_if<
  74                 Case6, mpl::identity<Type6>, mpl::eval_if<
  75                 Case7, mpl::identity<Type7>, mpl::eval_if<
  76                 Case8, mpl::identity<Type8>, mpl::eval_if<
  77                 Case9, mpl::identity<Type9>, mpl::eval_if<
  78                 Case10, mpl::identity<Type10>, mpl::eval_if<
  79                 Case11, mpl::identity<Type11>, mpl::if_<
  80                 Case12, Type12, mpl::void_ > > > > > > > > > > >
  81             >::type type;
  82 };
  83
  84 } } // End namespaces iostreams, boost.
  85
  86 #endif // #ifndef BOOST_IOSTREAMS_SELECT_HPP_INCLUDED