+
+ ; 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)
+(test-prog '(bool->int ((lambda (x) (x #f)) !)) 1)
+(test-prog '((lambda (f) (f #t)) bool->int) 1)
+(test-prog-stdout '(let () ((lambda (f) (f "foo")) print) 0) "foo")
+(test-prog '((lambda (f) (f 3 3)) (lambda (x y) (bool->int (= x y)))) 1)
+(test-prog '(bool->int ((lambda (f) (! (f 2 3))) =)) 1)
+
+ ; recursion (hangs at typechecking)
+(test-prog '(let [(fac (lambda (f n x) (if (= n 0) x (f f (- n 1) (* x x)))))]
+ (fac fac 3 2))
+ 8)