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Diffstat (limited to 'src/boost/libs/hana/example/lexicographical_compare.cpp')
-rw-r--r-- | src/boost/libs/hana/example/lexicographical_compare.cpp | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/src/boost/libs/hana/example/lexicographical_compare.cpp b/src/boost/libs/hana/example/lexicographical_compare.cpp new file mode 100644 index 000000000..5c70f59e8 --- /dev/null +++ b/src/boost/libs/hana/example/lexicographical_compare.cpp @@ -0,0 +1,39 @@ +// Copyright Louis Dionne 2013-2017 +// Distributed under the Boost Software License, Version 1.0. +// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) + +#include <boost/hana/assert.hpp> +#include <boost/hana/integral_constant.hpp> +#include <boost/hana/less.hpp> +#include <boost/hana/lexicographical_compare.hpp> +#include <boost/hana/tuple.hpp> +#include <boost/hana/type.hpp> +namespace hana = boost::hana; + + +int main() { + // works with elements whose `less` does not return a Constant + { + constexpr auto xs = hana::make_tuple(1, 2, 3, 4); + constexpr auto ys = hana::make_tuple(1, 6, 3, 4); + static_assert(hana::lexicographical_compare(xs, ys), ""); + } + + // and with those that do + { + auto xs = hana::make_tuple(hana::int_c<1>, hana::int_c<2>, hana::int_c<3>); + auto ys = hana::make_tuple(hana::int_c<1>, hana::int_c<5>, hana::int_c<3>); + BOOST_HANA_CONSTANT_CHECK(hana::lexicographical_compare(xs, ys)); + } + + // it also accepts a custom predicate + { + auto xs = hana::make_tuple(hana::type_c<int>, hana::type_c<char>, hana::type_c<void*>); + auto ys = hana::make_tuple(hana::type_c<int>, hana::type_c<long>, hana::type_c<void*>); + BOOST_HANA_CONSTANT_CHECK( + hana::lexicographical_compare(xs, ys, [](auto t, auto u) { + return hana::sizeof_(t) < hana::sizeof_(u); + }) + ); + } +} |