[29] | 1 | // Boost enable_if library |
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| 2 | |
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| 3 | // Copyright 2003 © The Trustees of Indiana University. |
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| 4 | |
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| 5 | // Use, modification, and distribution is subject to the Boost Software |
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| 6 | // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
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| 7 | // http://www.boost.org/LICENSE_1_0.txt) |
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| 8 | |
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| 9 | // Authors: Jaakko Järvi (jajarvi at osl.iu.edu) |
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| 10 | // Jeremiah Willcock (jewillco at osl.iu.edu) |
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| 11 | // Andrew Lumsdaine (lums at osl.iu.edu) |
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| 12 | |
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| 13 | |
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| 14 | #ifndef BOOST_UTILITY_ENABLE_IF_HPP |
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| 15 | #define BOOST_UTILITY_ENABLE_IF_HPP |
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| 16 | |
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| 17 | #include "boost/config.hpp" |
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| 18 | |
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| 19 | // Even the definition of enable_if causes problems on some compilers, |
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| 20 | // so it's macroed out for all compilers that do not support SFINAE |
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| 21 | |
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| 22 | #ifndef BOOST_NO_SFINAE |
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| 23 | |
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| 24 | namespace boost |
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| 25 | { |
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| 26 | |
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| 27 | template <bool B, class T = void> |
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| 28 | struct enable_if_c { |
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| 29 | typedef T type; |
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| 30 | }; |
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| 31 | |
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| 32 | template <class T> |
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| 33 | struct enable_if_c<false, T> {}; |
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| 34 | |
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| 35 | template <class Cond, class T = void> |
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| 36 | struct enable_if : public enable_if_c<Cond::value, T> {}; |
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| 37 | |
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| 38 | template <bool B, class T> |
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| 39 | struct lazy_enable_if_c { |
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| 40 | typedef typename T::type type; |
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| 41 | }; |
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| 42 | |
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| 43 | template <class T> |
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| 44 | struct lazy_enable_if_c<false, T> {}; |
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| 45 | |
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| 46 | template <class Cond, class T> |
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| 47 | struct lazy_enable_if : public lazy_enable_if_c<Cond::value, T> {}; |
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| 48 | |
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| 49 | |
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| 50 | template <bool B, class T = void> |
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| 51 | struct disable_if_c { |
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| 52 | typedef T type; |
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| 53 | }; |
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| 54 | |
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| 55 | template <class T> |
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| 56 | struct disable_if_c<true, T> {}; |
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| 57 | |
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| 58 | template <class Cond, class T = void> |
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| 59 | struct disable_if : public disable_if_c<Cond::value, T> {}; |
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| 60 | |
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| 61 | template <bool B, class T> |
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| 62 | struct lazy_disable_if_c { |
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| 63 | typedef typename T::type type; |
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| 64 | }; |
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| 65 | |
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| 66 | template <class T> |
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| 67 | struct lazy_disable_if_c<true, T> {}; |
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| 68 | |
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| 69 | template <class Cond, class T> |
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| 70 | struct lazy_disable_if : public lazy_disable_if_c<Cond::value, T> {}; |
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| 71 | |
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| 72 | } // namespace boost |
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| 73 | |
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| 74 | #else |
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| 75 | |
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| 76 | namespace boost { |
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| 77 | |
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| 78 | namespace detail { typedef void enable_if_default_T; } |
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| 79 | |
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| 80 | template <typename T> |
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| 81 | struct enable_if_does_not_work_on_this_compiler; |
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| 82 | |
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| 83 | template <bool B, class T = detail::enable_if_default_T> |
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| 84 | struct enable_if_c : enable_if_does_not_work_on_this_compiler<T> |
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| 85 | { }; |
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| 86 | |
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| 87 | template <bool B, class T = detail::enable_if_default_T> |
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| 88 | struct disable_if_c : enable_if_does_not_work_on_this_compiler<T> |
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| 89 | { }; |
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| 90 | |
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| 91 | template <bool B, class T = detail::enable_if_default_T> |
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| 92 | struct lazy_enable_if_c : enable_if_does_not_work_on_this_compiler<T> |
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| 93 | { }; |
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| 94 | |
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| 95 | template <bool B, class T = detail::enable_if_default_T> |
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| 96 | struct lazy_disable_if_c : enable_if_does_not_work_on_this_compiler<T> |
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| 97 | { }; |
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| 98 | |
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| 99 | template <class Cond, class T = detail::enable_if_default_T> |
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| 100 | struct enable_if : enable_if_does_not_work_on_this_compiler<T> |
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| 101 | { }; |
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| 102 | |
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| 103 | template <class Cond, class T = detail::enable_if_default_T> |
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| 104 | struct disable_if : enable_if_does_not_work_on_this_compiler<T> |
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| 105 | { }; |
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| 106 | |
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| 107 | template <class Cond, class T = detail::enable_if_default_T> |
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| 108 | struct lazy_enable_if : enable_if_does_not_work_on_this_compiler<T> |
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| 109 | { }; |
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| 110 | |
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| 111 | template <class Cond, class T = detail::enable_if_default_T> |
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| 112 | struct lazy_disable_if : enable_if_does_not_work_on_this_compiler<T> |
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| 113 | { }; |
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| 114 | |
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| 115 | } // namespace boost |
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| 116 | |
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| 117 | #endif // BOOST_NO_SFINAE |
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| 118 | |
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| 119 | #endif |
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