| 1 | // (C) Copyright Jonathan Turkanis 2003. |
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| 2 | // Distributed under the Boost Software License, Version 1.0. (See accompanying |
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| 3 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.) |
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| 4 | |
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| 5 | // See http://www.boost.org/libs/iostreams for documentation. |
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| 6 | |
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| 7 | // Contains the metafunction select, which mimics the effect of a chain of |
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| 8 | // nested mpl if_'s. |
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| 9 | // |
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| 10 | // ----------------------------------------------------------------------------- |
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| 11 | // |
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| 12 | // Usage: |
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| 13 | // |
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| 14 | // typedef typename select< |
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| 15 | // case1, type1, |
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| 16 | // case2, type2, |
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| 17 | // ... |
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| 18 | // true_, typen |
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| 19 | // >::type selection; |
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| 20 | // |
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| 21 | // Here case1, case2, ... are models of MPL::IntegralConstant with value type |
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| 22 | // bool, and n <= 10. |
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| 23 | |
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| 24 | #ifndef BOOST_IOSTREAMS_SELECT_HPP_INCLUDED |
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| 25 | #define BOOST_IOSTREAMS_SELECT_HPP_INCLUDED |
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| 26 | |
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| 27 | #if defined(_MSC_VER) && (_MSC_VER >= 1020) |
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| 28 | # pragma once |
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| 29 | #endif |
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| 30 | |
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| 31 | #include <boost/type_traits/is_base_and_derived.hpp> |
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| 32 | #include <boost/mpl/eval_if.hpp> |
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| 33 | #include <boost/mpl/identity.hpp> |
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| 34 | #include <boost/mpl/if.hpp> |
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| 35 | #include <boost/mpl/void.hpp> |
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| 36 | |
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| 37 | namespace boost { namespace iostreams { |
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| 38 | |
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| 39 | typedef mpl::true_ else_; |
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| 40 | |
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| 41 | template< typename Case1 = mpl::true_, |
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| 42 | typename Type1 = mpl::void_, |
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| 43 | typename Case2 = mpl::true_, |
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| 44 | typename Type2 = mpl::void_, |
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| 45 | typename Case3 = mpl::true_, |
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| 46 | typename Type3 = mpl::void_, |
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| 47 | typename Case4 = mpl::true_, |
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| 48 | typename Type4 = mpl::void_, |
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| 49 | typename Case5 = mpl::true_, |
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| 50 | typename Type5 = mpl::void_, |
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| 51 | typename Case6 = mpl::true_, |
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| 52 | typename Type6 = mpl::void_, |
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| 53 | typename Case7 = mpl::true_, |
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| 54 | typename Type7 = mpl::void_, |
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| 55 | typename Case8 = mpl::true_, |
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| 56 | typename Type8 = mpl::void_, |
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| 57 | typename Case9 = mpl::true_, |
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| 58 | typename Type9 = mpl::void_, |
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| 59 | typename Case10 = mpl::true_, |
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| 60 | typename Type10 = mpl::void_ > |
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| 61 | struct select { |
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| 62 | typedef typename |
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| 63 | mpl::eval_if< |
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| 64 | Case1, mpl::identity<Type1>, mpl::eval_if< |
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| 65 | Case2, mpl::identity<Type2>, mpl::eval_if< |
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| 66 | Case3, mpl::identity<Type3>, mpl::eval_if< |
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| 67 | Case4, mpl::identity<Type4>, mpl::eval_if< |
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| 68 | Case5, mpl::identity<Type5>, mpl::eval_if< |
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| 69 | Case6, mpl::identity<Type6>, mpl::eval_if< |
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| 70 | Case7, mpl::identity<Type7>, mpl::eval_if< |
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| 71 | Case8, mpl::identity<Type8>, mpl::eval_if< |
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| 72 | Case9, mpl::identity<Type9>, mpl::if_< |
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| 73 | Case10, Type10, mpl::void_ > > > > > > > > > |
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| 74 | >::type type; |
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| 75 | }; |
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| 76 | |
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| 77 | } } // End namespaces iostreams, boost. |
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| 78 | |
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| 79 | #endif // #ifndef BOOST_IOSTREAMS_SELECT_HPP_INCLUDED |
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