# [plt-scheme] match question

On Mon, May 12, 2008 at 11:34 PM, praimon <praimon at gmail.com> wrote:
>* thanks for your response. Would you say that the greediness of
*>* the patterns produces counter-intuitive answers?
*>* Here's a very simple example:
*>*
*>* (match '(3 2 4 3 2 1)
*>* ((list x y ... x z ...) (append y z)))
*>* => (2 4 3 2)
*>*
*>* Surely the result should be (2 4 2 1)? At least that's the intuitively
*>* correct answer (and the one returned by Mathematica, e.g.).
*>*
*>* Changing ... to ..1 produces a different counter-intuitive answer: (2 4 3 1).
*>* For people like me, who are merely using your language rather than trying
*>* to understand its inner workings, this is worrisome.
*
Neither of those are the right answer. There seems to be something
wrong with non-linear patterns (patterns where a variable appears
multiple times, like `x' does here) combined with ... I'll take a
look at it.
If you could file a bug report with that example (see the "Submit Bug
Report" entry under the Help menu) that would be great.
Thanks,
--
sam th
samth at ccs.neu.edu