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48 lines
1.8 KiB
48 lines
1.8 KiB
3 years ago
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/*=============================================================================
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Copyright (c) 2016 Lee Clagett
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Copyright (c) 2018 Kohei Takahashi
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Distributed under 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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==============================================================================*/
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#ifndef FUSION_AND_07152016_1625
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#define FUSION_AND_07152016_1625
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#include <boost/config.hpp>
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#include <boost/config/workaround.hpp>
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#include <boost/type_traits/integral_constant.hpp>
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#if defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
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#error fusion::detail::and_ requires variadic templates
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#endif
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namespace boost { namespace fusion { namespace detail {
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#if defined(BOOST_NO_CXX17_FOLD_EXPRESSIONS) \
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|| BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1913))
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template<typename ...Cond>
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struct and_impl : false_type {};
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template<typename ...T>
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struct and_impl<integral_constant<T, true>...> : true_type {};
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// This specialization is necessary to avoid MSVC-12 variadics bug.
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template<bool ...Cond>
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struct and_impl1 : and_impl<integral_constant<bool, Cond>...> {};
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/* fusion::detail::and_ differs from mpl::and_ in the following ways:
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- The empty set is valid and returns true
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- A single element set is valid and returns the identity
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- There is no upper bound on the set size
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- The conditions are evaluated at once, and are not short-circuited. This
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reduces instantations when returning true; the implementation is not
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recursive. */
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template<typename ...Cond>
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struct and_ : and_impl1<Cond::value...> {};
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#else
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template <typename ...Cond>
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struct and_ : integral_constant<bool, ((bool)Cond::value && ...)> {};
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#endif
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}}}
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#endif // FUSION_AND_07152016_1625
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