2.23.scm

; 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))
; Output:
; 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)
  (cond ((null? items) (newline))
        (else (proc (car items))
              (for-each proc (cdr items)))))

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