1 files changed, 25 insertions, 0 deletions
diff --git a/test/external/metalang99/examples/binary_tree.c b/test/external/metalang99/examples/binary_tree.c
new file mode 100644
index 0000000..8cd9177
--- /dev/null
+++ b/test/external/metalang99/examples/binary_tree.c
@@ -0,0 +1,25 @@
+// Sums all nodes of a binary tree, recursively.
+
+#include <metalang99.h>
+
+#define leaf(x)              ML99_choice(v(leaf), x)
+#define node(lhs, data, rhs) ML99_choice(v(node), lhs, data, rhs)
+
+#define sumTree(tree)                     ML99_match(tree, v(sumTree_))
+#define sumTree_leaf_IMPL(x)              v(x)
+#define sumTree_node_IMPL(lhs, data, rhs) ML99_add3(sumTree(v(lhs)), v(data), sumTree(v(rhs)))
+
+/*
+ *         4
+ *        / \
+ *       /   \
+ *      /     \
+ *     2       6
+ *    / \     / \
+ *   1   3   5   7
+ */
+#define TREE node(node(leaf(v(1)), v(2), leaf(v(3))), v(4), node(leaf(v(5)), v(6), leaf(v(7))))
+
+ML99_ASSERT_EQ(sumTree(TREE), v(28));
+
+int main(void) {}