1 files changed, 19 insertions, 0 deletions
diff --git a/src/third_party/js-1.7/Y.js b/src/third_party/js-1.7/Y.js
new file mode 100644
index 00000000000..e92a65a5df9
--- /dev/null
+++ b/src/third_party/js-1.7/Y.js
@@ -0,0 +1,19 @@
+// The Y combinator, applied to the factorial function
+
+function factorial(proc) {
+    return function (n) {
+        return (n <= 1) ? 1 : n * proc(n-1);
+    }
+}
+
+function Y(outer) {
+    function inner(proc) {
+        function apply(arg) {
+            return proc(proc)(arg);
+        }
+        return outer(apply);
+    }
+    return inner(inner);
+}
+
+print("5! is " + Y(factorial)(5));