Re: Will Fitzgerald <> Darius Bacon 11 Jan 1999 19:26 UTC

> Michael Sperber <xxxxxx@Informatik.Uni-Tuebingen.De> writes:
> >>>>>> "Will" == Will Fitzgerald <> writes:
> >
> >Will> May I suggest the following addition to the SRFI-1 list library,
> >Will> Common Lisp's LDIFF:
> >
> >Will> I think a reasonable definition is:
> >Will> [...]
> >[...]
> >Could you suggest possible uses for this procedure?

Here's a fairly trivial use taken from a real program:

(define parse-signature
  (lambda (spec)
    (let* ((mid (memq '- spec))
	   (in  (list-difference spec mid))
	   (out (cdr mid)))
      (make-signature in out))))

And here's another:

(define (butlast L)
  (list-difference L (last-pair L)))

But groveling through my source directories reveals fewer instances of
list-difference than I expected.