Add the Traversable type class.

test/traversable/sequence.cpp

@@ -0,0 +1,31 @@
+/*
+@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/traversable.hpp>
+
+#include <boost/hana/detail/minimal/applicative.hpp>
+#include <boost/hana/detail/minimal/comparable.hpp>
+#include <boost/hana/detail/minimal/traversable.hpp>
+#include <boost/hana/detail/static_assert.hpp>
+using namespace boost::hana;
+
+
+template <typename mcd>
+void test() {
+    constexpr auto traversable = detail::minimal::traversable<mcd>;
+    constexpr auto applicative = detail::minimal::applicative<>;
+    constexpr auto comparable = detail::minimal::comparable<>;
+
+    BOOST_HANA_STATIC_ASSERT(
+        sequence<detail::minimal::Applicative<>>(traversable(applicative(comparable(1))))
+            ==
+        applicative(traversable(comparable(1)))
+    );
+}
+
+int main() {
+    test<Traversable::traverse_mcd>();
+}