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.