2.23.rkt

#lang sicp
;; Exercise 2.23:
;; The procedure for-each is similar to map.
;; It takes as arguments a procedure and a list of elements.
;; However, rather than forming a list of the results,
;; for-each just applies the procedure to each of the elements in turn, from left to right.
;; The values returned by applying the procedure to the elements are not used at all for-each
;; is used with procedures that perform an action, such as printing.
;; For example,

(for-each
 (lambda (x) (newline) (display x))
 (list 57 321 88))

;; 57
;; 321
;; 88
;;
;; The value returned by the call to for-each (not illustrated above)
;; can be something arbitrary, such as true. Give an implementation of for-each.

(define (for-each proc items)
  ((proc (car items))
    (if (null? (cdr items))
      (proc (car items))
      (for-each proc (cdr items)))))