1 files changed, 30 insertions, 0 deletions
diff --git a/src/boost/libs/hana/example/lazy/comonad.cpp b/src/boost/libs/hana/example/lazy/comonad.cpp
new file mode 100644
index 000000000..39bbbea6b
--- /dev/null
+++ b/src/boost/libs/hana/example/lazy/comonad.cpp
@@ -0,0 +1,30 @@
+// 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/eval.hpp>
+#include <boost/hana/extend.hpp>
+#include <boost/hana/extract.hpp>
+#include <boost/hana/lazy.hpp>
+
+#include <sstream>
+namespace hana = boost::hana;
+
+
+int main() {
+    std::stringstream s("1 2 3");
+    auto i = hana::make_lazy([&] {
+        int i;
+        s >> i;
+        return i;
+    })();
+
+    auto i_plus_one = hana::extend(i, [](auto lazy_int) {
+        return hana::eval(lazy_int) + 1;
+    });
+
+    BOOST_HANA_RUNTIME_CHECK(hana::extract(i_plus_one) == 2);
+    BOOST_HANA_RUNTIME_CHECK(hana::extract(i_plus_one) == 3);
+    BOOST_HANA_RUNTIME_CHECK(hana::extract(i_plus_one) == 4);
+}