Dynamicly typed language with GC (optional explicit free).
define-generic
define-handler
define-data
match-data
(define-data exp?
(exp-var (name string?))
(exp-fn (name string?) (body exp?))
(exp-ap (target exp?) (arg exp?)))
(match-data exp? exp
((exp-var name) ...)
((exp-fn name body) ...)
((exp-ap target arg) ...))(declare add (-> nat? nat? nat?))
(define (add x y) ...)