1 files changed, 33 insertions, 0 deletions
diff --git a/src/boost/libs/hana/example/monadic_compose.cpp b/src/boost/libs/hana/example/monadic_compose.cpp
new file mode 100644
index 00000000..9c95ee7f
--- /dev/null
+++ b/src/boost/libs/hana/example/monadic_compose.cpp
@@ -0,0 +1,33 @@
+// 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/contains.hpp>
+#include <boost/hana/equal.hpp>
+#include <boost/hana/if.hpp>
+#include <boost/hana/monadic_compose.hpp>
+#include <boost/hana/optional.hpp>
+#include <boost/hana/tuple.hpp>
+#include <boost/hana/type.hpp>
+namespace hana = boost::hana;
+
+
+int main() {
+    BOOST_HANA_CONSTEXPR_LAMBDA auto block = [](auto ...types) {
+        return [=](auto x) {
+            return hana::if_(hana::contains(hana::make_tuple(types...), hana::typeid_(x)),
+                hana::nothing,
+                hana::just(x)
+            );
+        };
+    };
+
+    BOOST_HANA_CONSTEXPR_LAMBDA auto f = block(hana::type_c<double>);
+    BOOST_HANA_CONSTEXPR_LAMBDA auto g = block(hana::type_c<int>);
+    BOOST_HANA_CONSTEXPR_LAMBDA auto h = hana::monadic_compose(g, f);
+    BOOST_HANA_CONSTANT_CHECK(h(1)    == hana::nothing); // fails inside g; 1 has type int
+    BOOST_HANA_CONSTANT_CHECK(h(1.2)  == hana::nothing); // fails inside f; 1.2 has type double
+    BOOST_HANA_CONSTEXPR_CHECK(h('x') == hana::just('x')); // ok; 'x' has type char
+}