1 files changed, 28 insertions, 0 deletions
diff --git a/src/boost/libs/hana/example/tap.cpp b/src/boost/libs/hana/example/tap.cpp
new file mode 100644
index 000000000..6c93eeb55
--- /dev/null
+++ b/src/boost/libs/hana/example/tap.cpp
@@ -0,0 +1,28 @@
+// 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/chain.hpp>
+#include <boost/hana/equal.hpp>
+#include <boost/hana/tap.hpp>
+#include <boost/hana/tuple.hpp>
+
+#include <set>
+namespace hana = boost::hana;
+
+
+int main() {
+    // We use a sorted container because the order in which the functions
+    // are called is unspecified.
+    std::set<int> before, after;
+
+    auto xs = hana::make_tuple(1, 2, 3)
+        | hana::tap<hana::tuple_tag>([&](int x) { before.insert(x); })
+        | [](auto x) { return hana::make_tuple(x, -x); }
+        | hana::tap<hana::tuple_tag>([&](int x) { after.insert(x); });
+
+    BOOST_HANA_RUNTIME_CHECK(before == std::set<int>{1, 2, 3});
+    BOOST_HANA_RUNTIME_CHECK(after == std::set<int>{1, -1, 2, -2, 3, -3});
+    BOOST_HANA_RUNTIME_CHECK(xs == hana::make_tuple(1, -1, 2, -2, 3, -3));
+}