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122 lines
3.0 KiB
122 lines
3.0 KiB
// Copyright David Abrahams 2004. Use, modification and distribution is
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// subject to the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef IS_INCREMENTABLE_DWA200415_HPP
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# define IS_INCREMENTABLE_DWA200415_HPP
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# include <boost/type_traits/integral_constant.hpp>
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# include <boost/type_traits/remove_cv.hpp>
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# include <boost/detail/workaround.hpp>
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namespace boost { namespace detail {
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// is_incrementable<T> metafunction
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//
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// Requires: Given x of type T&, if the expression ++x is well-formed
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// it must have complete type; otherwise, it must neither be ambiguous
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// nor violate access.
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// This namespace ensures that ADL doesn't mess things up.
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namespace is_incrementable_
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{
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// a type returned from operator++ when no increment is found in the
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// type's own namespace
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struct tag {};
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// any soaks up implicit conversions and makes the following
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// operator++ less-preferred than any other such operator that
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// might be found via ADL.
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struct any { template <class T> any(T const&); };
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// This is a last-resort operator++ for when none other is found
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# if BOOST_WORKAROUND(__GNUC__, == 4) && __GNUC_MINOR__ == 0 && __GNUC_PATCHLEVEL__ == 2
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}
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namespace is_incrementable_2
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{
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is_incrementable_::tag operator++(is_incrementable_::any const&);
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is_incrementable_::tag operator++(is_incrementable_::any const&,int);
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}
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using namespace is_incrementable_2;
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namespace is_incrementable_
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{
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# else
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tag operator++(any const&);
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tag operator++(any const&,int);
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# endif
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# if BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3202))
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# define BOOST_comma(a,b) (a)
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# else
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// In case an operator++ is found that returns void, we'll use ++x,0
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tag operator,(tag,int);
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# define BOOST_comma(a,b) (a,b)
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# endif
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# if defined(BOOST_MSVC)
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# pragma warning(push)
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# pragma warning(disable:4913) // Warning about operator,
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# endif
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// two check overloads help us identify which operator++ was picked
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char (& check_(tag) )[2];
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template <class T>
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char check_(T const&);
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template <class T>
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struct impl
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{
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static typename boost::remove_cv<T>::type& x;
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BOOST_STATIC_CONSTANT(
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bool
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, value = sizeof(is_incrementable_::check_(BOOST_comma(++x,0))) == 1
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);
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};
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template <class T>
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struct postfix_impl
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{
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static typename boost::remove_cv<T>::type& x;
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BOOST_STATIC_CONSTANT(
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bool
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, value = sizeof(is_incrementable_::check_(BOOST_comma(x++,0))) == 1
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);
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};
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# if defined(BOOST_MSVC)
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# pragma warning(pop)
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# endif
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}
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# undef BOOST_comma
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template<typename T>
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struct is_incrementable :
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public boost::integral_constant<bool, boost::detail::is_incrementable_::impl<T>::value>
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{
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};
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template<typename T>
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struct is_postfix_incrementable :
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public boost::integral_constant<bool, boost::detail::is_incrementable_::postfix_impl<T>::value>
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{
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};
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} // namespace detail
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} // namespace boost
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# include <boost/type_traits/detail/bool_trait_undef.hpp>
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#endif // IS_INCREMENTABLE_DWA200415_HPP
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