1 files changed, 38 insertions, 0 deletions
diff --git a/src/boost/libs/hana/example/fold.cpp b/src/boost/libs/hana/example/fold.cpp
new file mode 100644
index 000000000..a351be580
--- /dev/null
+++ b/src/boost/libs/hana/example/fold.cpp
@@ -0,0 +1,38 @@
+// 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/fold.hpp>
+#include <boost/hana/tuple.hpp>
+
+#include <sstream>
+#include <string>
+namespace hana = boost::hana;
+
+
+auto to_string = [](auto x) {
+    std::ostringstream ss;
+    ss << x;
+    return ss.str();
+};
+
+int main() {
+    auto f = [=](std::string s, auto element) {
+        return "f(" + s + ", " + to_string(element) + ")";
+    };
+
+    // with an initial state
+    BOOST_HANA_RUNTIME_CHECK(
+        hana::fold(hana::make_tuple(2, '3', 4, 5.0), "1", f)
+            ==
+        "f(f(f(f(1, 2), 3), 4), 5)"
+    );
+
+    // without initial state
+    BOOST_HANA_RUNTIME_CHECK(
+        hana::fold(hana::make_tuple("1", 2, '3', 4, 5.0), f)
+            ==
+        "f(f(f(f(1, 2), 3), 4), 5)"
+    );
+}