Add the Traversable type class.

example/list/traversable/sequence.cpp

@@ -0,0 +1,33 @@
+/*
+@copyright Louis Dionne 2014
+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/list.hpp>
+
+#include <cassert>
+#include <string>
+using namespace boost::hana;
+using namespace std::string_literals;
+
+
+int main() {
+    //! [main]
+    assert(
+        sequence<List>(
+            list(list("a1"s, "a2"s), list("b1"s), list("c1", "c2", "c3"))
+        )
+        ==
+        list(
+            list("a1"s, "b1"s, "c1"s),
+            list("a1"s, "b1"s, "c2"s),
+            list("a1"s, "b1"s, "c3"s),
+
+            list("a2"s, "b1"s, "c1"s),
+            list("a2"s, "b1"s, "c2"s),
+            list("a2"s, "b1"s, "c3"s)
+        )
+    );
+    //! [main]
+}