(test-prog '((lambda (x y) (+ x y)) 1 2) 3)
(test-prog '((lambda (x) (+ ((lambda (y) (+ y 1)) 3) x)) 2) 6)
+
+ ; passing closures about
+(test-prog '((lambda (z) ((lambda (x) (x 1)) (lambda (y) (+ z y)))) 2) 3)
+
+ ; passing builtins about
+(test-prog '((lambda (x) ((lambda (a b) (a b 3)) + x)) 3) 6)