57 lines
1.5 KiB
C++
57 lines
1.5 KiB
C++
// Copyright Louis Dionne 2013-2017
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// Copyright Jason Rice 2017
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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#ifndef TEST_SUPPORT_COUNTER_HPP
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#define TEST_SUPPORT_COUNTER_HPP
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#include <boost/hana/fwd/at.hpp>
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#include <boost/hana/fwd/concept/iterable.hpp>
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#include <boost/hana/fwd/drop_front.hpp>
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#include <boost/hana/fwd/is_empty.hpp>
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#include <boost/hana/integral_constant.hpp>
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// Counter - an infinite iterable for the masses
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struct Counter_tag { };
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template <std::size_t N = 0>
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struct Counter {
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using hana_tag = Counter_tag;
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static constexpr std::size_t value = N;
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};
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namespace boost { namespace hana {
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//////////////////////////////////////////////////////////////////////////
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// Iterable
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//////////////////////////////////////////////////////////////////////////
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template <>
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struct at_impl<Counter_tag> {
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template <typename T, typename N>
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static constexpr decltype(auto) apply(T, N) {
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return hana::size_c<T::value + N::value>;
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}
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};
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template <>
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struct drop_front_impl<Counter_tag> {
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template <typename T, typename N>
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static constexpr auto apply(T, N) {
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return Counter<T::value + N::value>{};
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}
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};
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template <>
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struct is_empty_impl<Counter_tag> {
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template <typename Xs>
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static constexpr auto apply(Xs)
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-> hana::false_
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{ return {}; }
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};
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}} // end namespace boost::hana
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#endif // !TEST_SUPPORT_COUNTER_HPP
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