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os/ossrv/ossrv_pub/boost_apis/boost/iostreams/detail/select.hpp
author sl@SLION-WIN7.fritz.box
Fri, 15 Jun 2012 03:10:57 +0200
changeset 0 bde4ae8d615e
permissions -rw-r--r--
First public contribution. 
     1 // (C) Copyright Jonathan Turkanis 2003.

     2 // Distributed under the Boost Software License, Version 1.0. (See accompanying

     3 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)

     4 

     5 // See http://www.boost.org/libs/iostreams for documentation.

     6 

     7 // Contains the metafunction select, which mimics the effect of a chain of

     8 // nested mpl if_'s.

     9 //

    10 // -----------------------------------------------------------------------------

    11 //

    12 // Usage:

    13 //      

    14 // typedef typename select<

    15 //                      case1,  type1,

    16 //                      case2,  type2,

    17 //                      ...

    18 //                      true_,  typen

    19 //                  >::type selection;

    20 //

    21 // Here case1, case2, ... are models of MPL::IntegralConstant with value type

    22 // bool, and n <= 10.

    23 

    24 #ifndef BOOST_IOSTREAMS_SELECT_HPP_INCLUDED

    25 #define BOOST_IOSTREAMS_SELECT_HPP_INCLUDED   

    26 

    27 #if defined(_MSC_VER) && (_MSC_VER >= 1020)

    28 # pragma once

    29 #endif                  

    30  

    31 #include <boost/type_traits/is_base_and_derived.hpp>

    32 #include <boost/mpl/eval_if.hpp>

    33 #include <boost/mpl/identity.hpp>

    34 #include <boost/mpl/if.hpp>

    35 #include <boost/mpl/void.hpp>

    36 

    37 namespace boost { namespace iostreams { 

    38 

    39 typedef mpl::true_ else_;

    40 

    41 template< typename Case1 = mpl::true_,

    42           typename Type1 = mpl::void_,

    43           typename Case2 = mpl::true_,

    44           typename Type2 = mpl::void_,

    45           typename Case3 = mpl::true_,

    46           typename Type3 = mpl::void_,

    47           typename Case4 = mpl::true_,

    48           typename Type4 = mpl::void_,

    49           typename Case5 = mpl::true_,

    50           typename Type5 = mpl::void_,

    51           typename Case6 = mpl::true_,

    52           typename Type6 = mpl::void_,

    53           typename Case7 = mpl::true_,

    54           typename Type7 = mpl::void_,

    55           typename Case8 = mpl::true_,

    56           typename Type8 = mpl::void_,

    57           typename Case9 = mpl::true_,

    58           typename Type9 = mpl::void_,

    59           typename Case10 = mpl::true_,

    60           typename Type10 = mpl::void_ >

    61 struct select {

    62     typedef typename

    63             mpl::eval_if<

    64                 Case1, mpl::identity<Type1>, mpl::eval_if<

    65                 Case2, mpl::identity<Type2>, mpl::eval_if<

    66                 Case3, mpl::identity<Type3>, mpl::eval_if<

    67                 Case4, mpl::identity<Type4>, mpl::eval_if<

    68                 Case5, mpl::identity<Type5>, mpl::eval_if<

    69                 Case6, mpl::identity<Type6>, mpl::eval_if<

    70                 Case7, mpl::identity<Type7>, mpl::eval_if<

    71                 Case8, mpl::identity<Type8>, mpl::eval_if<

    72                 Case9, mpl::identity<Type9>, mpl::if_<

    73                 Case10, Type10, mpl::void_ > > > > > > > > >

    74             >::type type;

    75 };

    76 

    77 } } // End namespaces iostreams, boost.

    78 

    79 #endif // #ifndef BOOST_IOSTREAMS_SELECT_HPP_INCLUDED
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