chez-scheme-map-imp.scm

(define map
  (lambda (f ls . more)
    (if (null? more)
	(let map1 ((ls ls))
	  (if (null? ls)
	      '()
	      (cons (f (car ls))
		    (map1 (cdr ls)))))
	(let map-more ((ls ls) (more more))
	  (if (null? ls)
	      '()
	      (cons (apply f (car ls) (map car more))
		    (map-more (cdr ls)
			      (map cdr more))))))))