40 lines
1.4 KiB
C++
40 lines
1.4 KiB
C++
// Copyright Louis Dionne 2013-2017
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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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#include <boost/hana/assert.hpp>
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#include <boost/hana/integral_constant.hpp>
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#include <boost/hana/less.hpp>
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#include <boost/hana/lexicographical_compare.hpp>
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#include <boost/hana/tuple.hpp>
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#include <boost/hana/type.hpp>
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namespace hana = boost::hana;
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int main() {
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// works with elements whose `less` does not return a Constant
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{
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constexpr auto xs = hana::make_tuple(1, 2, 3, 4);
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constexpr auto ys = hana::make_tuple(1, 6, 3, 4);
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static_assert(hana::lexicographical_compare(xs, ys), "");
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}
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// and with those that do
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{
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auto xs = hana::make_tuple(hana::int_c<1>, hana::int_c<2>, hana::int_c<3>);
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auto ys = hana::make_tuple(hana::int_c<1>, hana::int_c<5>, hana::int_c<3>);
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BOOST_HANA_CONSTANT_CHECK(hana::lexicographical_compare(xs, ys));
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}
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// it also accepts a custom predicate
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{
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auto xs = hana::make_tuple(hana::type_c<int>, hana::type_c<char>, hana::type_c<void*>);
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auto ys = hana::make_tuple(hana::type_c<int>, hana::type_c<long>, hana::type_c<void*>);
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BOOST_HANA_CONSTANT_CHECK(
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hana::lexicographical_compare(xs, ys, [](auto t, auto u) {
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return hana::sizeof_(t) < hana::sizeof_(u);
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})
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);
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}
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}
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