Re: pattern matching
- To: mathgroup at smc.vnet.net
- Subject: [mg7014] Re: pattern matching
- From: Dick Zacher <dick at loc3.tandem.com>
- Date: Thu, 1 May 1997 14:48:58 -0400 (EDT)
- Organization: Tandem Computers
- Sender: owner-wri-mathgroup at wolfram.com
Marc Mazzariol wrote:
>
> Hello,
>
> I'm using mathematica 2.2 (Unix), and i'm trying to do pattern
> matching with repeated patterns.
>
> This example produce the result i want :
>
> In : {a,a,a,b} /. {a...,b} -> Hello
> Out : Hello
>
> But this one don't :
>
> In : {b} /. {a...,b} -> Hello
> Out : {b}
>
> I was hopping : Out : Hello
>
Marc,
I ran into the same problem myself 5 years ago with version 2.0.4. It
appeared to be a defect in the software: The function RepeatedNull did
not work correctly -- it failed to match the absence of any element. I
reported the problem to WRI at the time, but perhaps it did not get
fixed in the next 2 releases.
In Version 3.0 RepeatedNull does work and gives the results you were
expecting. (I just tested it!)
Dick
--
-----------------------------
Dick Zacher
Performance Engineering Dept., Tandem Computers
zacher_dick at tandem.com phone: 408-285-5746 fax: 408-285-7079