(unit/sig
   (collect)
   (import (u : plt:userspace^))



;; collect
;; given a base-case "base" and a rule "combine" for combining a list,
;; the first thing in the list, and the recursive call,
;; return:
;;    a function which actually goes
;;    and calls combine on each list recursevely,
;;    collecting the result and returning it.
;;
(define collect
  (lambda (base combine)
     (local ((define C
               (lambda (l)
                  (cond
                     ((null? l) base)
                     (else (combine l (car l) (C (cdr l))))))))
        C)))

)