[3408] | 1 | // Copyright David Abrahams 2004. Use, modification and distribution is |
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| 2 | // subject to 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 | #ifndef IS_INCREMENTABLE_DWA200415_HPP |
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| 5 | # define IS_INCREMENTABLE_DWA200415_HPP |
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| 6 | |
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| 7 | # include <boost/type_traits/detail/template_arity_spec.hpp> |
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| 8 | # include <boost/type_traits/remove_cv.hpp> |
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| 9 | # include <boost/mpl/aux_/lambda_support.hpp> |
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| 10 | # include <boost/mpl/bool.hpp> |
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| 11 | # include <boost/detail/workaround.hpp> |
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| 12 | |
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| 13 | // Must be the last include |
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| 14 | # include <boost/type_traits/detail/bool_trait_def.hpp> |
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| 15 | |
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| 16 | namespace boost { namespace detail { |
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| 17 | |
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| 18 | // is_incrementable<T> metafunction |
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| 19 | // |
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| 20 | // Requires: Given x of type T&, if the expression ++x is well-formed |
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| 21 | // it must have complete type; otherwise, it must neither be ambiguous |
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| 22 | // nor violate access. |
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| 23 | |
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| 24 | // This namespace ensures that ADL doesn't mess things up. |
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| 25 | namespace is_incrementable_ |
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| 26 | { |
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| 27 | // a type returned from operator++ when no increment is found in the |
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| 28 | // type's own namespace |
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| 29 | struct tag {}; |
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| 30 | |
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| 31 | // any soaks up implicit conversions and makes the following |
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| 32 | // operator++ less-preferred than any other such operator that |
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| 33 | // might be found via ADL. |
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| 34 | struct any { template <class T> any(T const&); }; |
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| 35 | |
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| 36 | // This is a last-resort operator++ for when none other is found |
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| 37 | # if BOOST_WORKAROUND(__GNUC__, == 4) && __GNUC_MINOR__ == 0 && __GNUC_PATCHLEVEL__ == 2 |
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| 38 | |
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| 39 | } |
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| 40 | |
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| 41 | namespace is_incrementable_2 |
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| 42 | { |
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| 43 | is_incrementable_::tag operator++(is_incrementable_::any const&); |
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| 44 | is_incrementable_::tag operator++(is_incrementable_::any const&,int); |
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| 45 | } |
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| 46 | using namespace is_incrementable_2; |
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| 47 | |
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| 48 | namespace is_incrementable_ |
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| 49 | { |
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| 50 | |
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| 51 | # else |
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| 52 | |
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| 53 | tag operator++(any const&); |
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| 54 | tag operator++(any const&,int); |
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| 55 | |
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| 56 | # endif |
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| 57 | |
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| 58 | # if BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3202)) \ |
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| 59 | || BOOST_WORKAROUND(BOOST_MSVC, <= 1300) |
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| 60 | # define BOOST_comma(a,b) (a) |
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| 61 | # else |
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| 62 | // In case an operator++ is found that returns void, we'll use ++x,0 |
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| 63 | tag operator,(tag,int); |
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| 64 | # define BOOST_comma(a,b) (a,b) |
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| 65 | # endif |
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| 66 | |
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| 67 | # if defined(BOOST_MSVC) |
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| 68 | # pragma warning(push) |
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| 69 | # pragma warning(disable:4913) // Warning about operator, |
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| 70 | # endif |
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| 71 | |
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| 72 | // two check overloads help us identify which operator++ was picked |
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| 73 | char (& check(tag) )[2]; |
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| 74 | |
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| 75 | template <class T> |
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| 76 | char check(T const&); |
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| 77 | |
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| 78 | |
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| 79 | template <class T> |
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| 80 | struct impl |
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| 81 | { |
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| 82 | static typename boost::remove_cv<T>::type& x; |
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| 83 | |
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| 84 | BOOST_STATIC_CONSTANT( |
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| 85 | bool |
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| 86 | , value = sizeof(is_incrementable_::check(BOOST_comma(++x,0))) == 1 |
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| 87 | ); |
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| 88 | }; |
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| 89 | |
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| 90 | template <class T> |
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| 91 | struct postfix_impl |
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| 92 | { |
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| 93 | static typename boost::remove_cv<T>::type& x; |
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| 94 | |
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| 95 | BOOST_STATIC_CONSTANT( |
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| 96 | bool |
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| 97 | , value = sizeof(is_incrementable_::check(BOOST_comma(x++,0))) == 1 |
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| 98 | ); |
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| 99 | }; |
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| 100 | |
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| 101 | # if defined(BOOST_MSVC) |
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| 102 | # pragma warning(pop) |
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| 103 | # endif |
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| 104 | |
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| 105 | } |
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| 106 | |
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| 107 | # undef BOOST_comma |
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| 108 | |
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| 109 | template<typename T> |
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| 110 | struct is_incrementable |
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| 111 | BOOST_TT_AUX_BOOL_C_BASE(::boost::detail::is_incrementable_::impl<T>::value) |
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| 112 | { |
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| 113 | BOOST_TT_AUX_BOOL_TRAIT_VALUE_DECL(::boost::detail::is_incrementable_::impl<T>::value) |
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| 114 | BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_incrementable,(T)) |
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| 115 | }; |
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| 116 | |
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| 117 | template<typename T> |
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| 118 | struct is_postfix_incrementable |
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| 119 | BOOST_TT_AUX_BOOL_C_BASE(::boost::detail::is_incrementable_::impl<T>::value) |
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| 120 | { |
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| 121 | BOOST_TT_AUX_BOOL_TRAIT_VALUE_DECL(::boost::detail::is_incrementable_::postfix_impl<T>::value) |
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| 122 | BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_postfix_incrementable,(T)) |
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| 123 | }; |
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| 124 | |
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| 125 | } // namespace detail |
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| 126 | |
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| 127 | BOOST_TT_AUX_TEMPLATE_ARITY_SPEC(1, ::boost::detail::is_incrementable) |
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| 128 | BOOST_TT_AUX_TEMPLATE_ARITY_SPEC(1, ::boost::detail::is_postfix_incrementable) |
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| 129 | |
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| 130 | } // namespace boost |
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| 131 | |
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| 132 | # include <boost/type_traits/detail/bool_trait_undef.hpp> |
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| 133 | |
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| 134 | #endif // IS_INCREMENTABLE_DWA200415_HPP |
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