interp con ambientes
;; interp : FAE DefrdSub → FAE-Value
(define (interp expr ds)
(type-case FAE expr
[num (n) (numV n)]
[add (l r) (num+ (interp l ds) (interp r ds))]
[id (v) (lookup v ds)]
[fun (bound-id bound-body)
(closureV bound-id bound-body ds)]
[app (fun-expr arg-expr)
(local ([define fun-val (interp fun-expr ds)])
(interp (closureV-body fun-val)
(aSub (closureV-param fun-val)
(interp arg-expr ds)
(closureV-ds fun-val))))]))