111 lines
4.3 KiB
C++
111 lines
4.3 KiB
C++
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/*!
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@file
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Defines `boost::hana::lexicographical_compare`.
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@copyright Louis Dionne 2013-2016
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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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*/
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#ifndef BOOST_HANA_LEXICOGRAPHICAL_COMPARE_HPP
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#define BOOST_HANA_LEXICOGRAPHICAL_COMPARE_HPP
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#include <boost/hana/fwd/lexicographical_compare.hpp>
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#include <boost/hana/bool.hpp>
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#include <boost/hana/concept/iterable.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/dispatch.hpp>
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#include <boost/hana/drop_front.hpp>
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#include <boost/hana/front.hpp>
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#include <boost/hana/if.hpp>
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#include <boost/hana/is_empty.hpp>
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#include <boost/hana/less.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @cond
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template <typename Xs, typename Ys>
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constexpr auto lexicographical_compare_t::operator()(Xs const& xs, Ys const& ys) const {
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return hana::lexicographical_compare(xs, ys, hana::less);
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}
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template <typename Xs, typename Ys, typename Pred>
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constexpr auto lexicographical_compare_t::operator()(Xs const& xs, Ys const& ys, Pred const& pred) const {
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using It1 = typename hana::tag_of<Xs>::type;
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using It2 = typename hana::tag_of<Ys>::type;
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using LexicographicalCompare = BOOST_HANA_DISPATCH_IF(
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lexicographical_compare_impl<It1>,
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hana::Iterable<It1>::value &&
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hana::Iterable<It2>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::Iterable<It1>::value,
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"hana::lexicographical_compare(xs, ys, pred) requires 'xs' to be Iterable");
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static_assert(hana::Iterable<It2>::value,
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"hana::lexicographical_compare(xs, ys, pred) requires 'ys' to be Iterable");
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#endif
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return LexicographicalCompare::apply(xs, ys, pred);
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}
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//! @endcond
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template <typename It, bool condition>
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struct lexicographical_compare_impl<It, when<condition>> : default_ {
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template <typename Xs, typename Ys, typename Pred>
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static constexpr auto
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helper2(Xs const&, Ys const&, Pred const&, hana::true_)
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{ return hana::false_c; }
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template <typename Xs, typename Ys, typename Pred>
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static constexpr auto
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helper2(Xs const& xs, Ys const& ys, Pred const& pred, hana::false_)
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{ return apply(hana::drop_front(xs), hana::drop_front(ys), pred); }
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template <typename Xs, typename Ys, typename Pred>
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static constexpr auto
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helper2(Xs const& xs, Ys const& ys, Pred const& pred, bool is_greater)
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{ return is_greater ? false : apply(hana::drop_front(xs), hana::drop_front(ys), pred); }
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template <typename Xs, typename Ys, typename Pred>
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static constexpr auto
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helper1(Xs const&, Ys const&, Pred const&, hana::true_)
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{ return hana::true_c; }
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template <typename Xs, typename Ys, typename Pred>
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static constexpr auto
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helper1(Xs const& xs, Ys const& ys, Pred const& pred, hana::false_)
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{ return helper2(xs, ys, pred, hana::if_(pred(hana::front(ys), hana::front(xs)), hana::true_c, hana::false_c)); }
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template <typename Xs, typename Ys, typename Pred>
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static constexpr auto
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helper1(Xs const& xs, Ys const& ys, Pred const& pred, bool is_less)
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{ return is_less ? true : helper2(xs, ys, pred, hana::if_(pred(hana::front(ys), hana::front(xs)), hana::true_c, hana::false_c)); }
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template <typename Xs, typename Ys, typename Pred>
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static constexpr auto
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helper(Xs const&, Ys const& ys, Pred const&, hana::true_)
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{ return hana::not_(hana::is_empty(ys)); }
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template <typename Xs, typename Ys, typename Pred>
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static constexpr auto
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helper(Xs const& xs, Ys const& ys, Pred const& pred, hana::false_)
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{ return helper1(xs, ys, pred, hana::if_(pred(hana::front(xs), hana::front(ys)), hana::true_c, hana::false_c)); }
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template <typename Xs, typename Ys, typename Pred>
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static constexpr auto apply(Xs const& xs, Ys const& ys, Pred const& pred) {
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return helper(xs, ys, pred, hana::bool_c<
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decltype(hana::is_empty(xs))::value ||
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decltype(hana::is_empty(ys))::value
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>);
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}
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_LEXICOGRAPHICAL_COMPARE_HPP
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