gistfile1.rkt

(define evens-only*&co
  (lambda (l col)
    (cond
     [(null? l) (col '() 1 0)]
     [(atom? (car l))
      (cond
       [(not (even? (car l)))
	(evens-only*&co (cdr l)
			(lambda (newlat E U)
			  (col newlat E (+ U (car l)))))]
       [else
	(evens-only*&co (cdr l)
			(lambda (newlat E U)
			  (col (cons (car l) newlat) (* E (car l)) U)))])]
     [else
      (evens-only*&co (car l)
		      (lambda (newlat E U)
			(col (cons
			      (car l)
			      (evens-only*&co
			       (cdr l)
			       (lambda (newlat E U)
				 (col (cdr l) E U)))) E U)))])))