+
+ ; 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
+(test-prog '(let [(inc (lambda (f n x)
+ (if (= n 0)
+ x
+ (f f (- n 1) (+ x 1)))))]
+ (inc inc 3 2))
+ 5)
+
+(test-prog '(let ([go (lambda (n m x)
+ (if (= n 0)
+ x
+ (go (- n 1) m (* x m))))]
+ [pow (lambda (p y) (go p y 1))])
+
+ (pow 3 2))
+ 8)
+
+(test-prog '(let ([pow (lambda (p y)
+ (let ([go (lambda (n x)
+ (if (= n 0)
+ x
+ (go (- n 1) (* x y))))])
+ (go p 1)))])
+ (pow 4 2))
+ 16)