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Diffstat (limited to 'src/boost/libs/hana/example/tuple/foldable.cpp')
-rw-r--r-- | src/boost/libs/hana/example/tuple/foldable.cpp | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/src/boost/libs/hana/example/tuple/foldable.cpp b/src/boost/libs/hana/example/tuple/foldable.cpp new file mode 100644 index 000000000..8a5354e39 --- /dev/null +++ b/src/boost/libs/hana/example/tuple/foldable.cpp @@ -0,0 +1,26 @@ +// 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/config.hpp> +#include <boost/hana/equal.hpp> +#include <boost/hana/fold_right.hpp> +#include <boost/hana/if.hpp> +#include <boost/hana/less.hpp> +#include <boost/hana/prepend.hpp> +#include <boost/hana/tuple.hpp> +namespace hana = boost::hana; +using namespace hana::literals; + + +int main() { + constexpr auto numbers = hana::tuple_c<int, 5, -1, 0, -7, -2, 0, -5, 4>; + constexpr auto negatives = hana::tuple_c<int, -1, -7, -2, -5>; + + BOOST_HANA_CONSTEXPR_LAMBDA auto keep_negatives = [](auto n, auto acc) { + return hana::if_(n < 0_c, hana::prepend(acc, n), acc); + }; + + BOOST_HANA_CONSTANT_CHECK(hana::fold_right(numbers, hana::tuple_c<int>, keep_negatives) == negatives); +} |