ADD: nested function.

ADD: function can returns other function or lambda.

examples/fun.gri

@@ -29,3 +29,24 @@
             (if (eq? x 0)
                 1
                 (* x (self (- x 1))))) 6))
+
+;; inner functions
+($ (f n)
+  ($ (inner n) (+ n 1))
+  (inner (inner n)))
+
+(assert-eq? 3 (f 1))
+
+;; return function
+($ (g)
+   ($ (inner n) (* 7 n))
+   inner)
+
+(assert-eq? 42 ( (g) 6 ))
+
+;; return lambda
+($ (h)
+   (-> (n)
+       (* 3 (- n 2))))
+
+(assert-eq? 15 ( (h) 7 ))