1 files changed, 26 insertions, 0 deletions
diff --git a/src/boost/libs/hana/example/string/foldable.cpp b/src/boost/libs/hana/example/string/foldable.cpp
new file mode 100644
index 000000000..d1d4661ec
--- /dev/null
+++ b/src/boost/libs/hana/example/string/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/equal.hpp>
+#include <boost/hana/fold_left.hpp>
+#include <boost/hana/integral_constant.hpp>
+#include <boost/hana/plus.hpp>
+#include <boost/hana/string.hpp>
+#include <boost/hana/value.hpp>
+namespace hana = boost::hana;
+
+
+int main() {
+    auto sum_string = [](auto str) {
+        return hana::fold_left(str, hana::int_c<0>, [](auto sum, auto c) {
+            constexpr int i = hana::value(c) - 48; // convert character to decimal
+            return sum + hana::int_c<i>;
+        });
+    };
+
+    BOOST_HANA_CONSTANT_CHECK(
+        sum_string(BOOST_HANA_STRING("1234")) == hana::int_c<1 + 2 + 3 + 4>
+    );
+}