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
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+++ 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);
+}