my attempt to do the exercises in sicp.

Wednesday, July 16, 2008

sicp exercise 2.23

;  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 (lambda (proc items)
  (cond ((null? items) 1)
         (else (proc (car items)) (for-each proc (cdr items))))))

(for-each (lambda(x) (display x)(newline)) (list 1 2 3 4 5))

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