Steve Schafer  <pandeng@telepath.com> wrote:
+---------------
|  (define (indexof item list)
|    (define (internal-indexof item list count)
|      (if (or (null? list) (= count 0))
|        0
|        (if (eq? item (car list))
|          count
|          (internal-indexof item (cdr list) (+ count 1)))))
|    (internal-indexof item list 1))
+---------------

What's up with that "(= count 0)" term?  It doesn't do anything useful,
since it can never be true. Why not just:

   (define (indexof item list)
     (define (internal-indexof item list count)
       (cond
	 ((null? list) #f)
         ((eq? item (car list)) count)
	 (else (internal-indexof item (cdr list) (+ count 1)))))
     (internal-indexof item list 1))

Note: I've also changed the "not-found" return value from "0" to "#f",
since that's more in line with the rest of Scheme (member, assoc, etc.).

Finally, although the original poster specified a "1-based" result, a
0-based result is more in keeping with a name like "index". I would
encourage him to change the spec of "indexof" to give a 0-based result,
and thus change the last expr above to (internal-indexof item list 0)
so that (indexof 'a '(c b a d e f)) ==> 2.


-Rob

-----
Rob Warnock, 31-2-510		rpw3@sgi.com
Network Engineering		http://reality.sgi.com/rpw3/
Silicon Graphics, Inc.		Phone: 650-933-1673
1600 Amphitheatre Pkwy.		PP-ASEL-IA
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