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MathGroup Archive 2005

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Re: Problem with matching.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53913] Re: [mg53907] Problem with matching.
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Fri, 4 Feb 2005 04:11:08 -0500 (EST)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

F[{___,a_,___}]F[{___,a_,___}]//FullForm

Power[F[List[BlankNullSequence[],Pattern[a,Blank[]],BlankNullSequence[]]],2]

The two terms on the LHS of the rule are identical so they are multiplied to 
form F^2.  Use the following:

F[{x,2,c}]F[{x,1,f}]/.F[{___,a_,___}]F[{___,b_,___}]/;a==b:>yes

yes


Bob Hanlon

> 
> From: Josef Karthauser <joe at tao.org.uk>
To: mathgroup at smc.vnet.net
> Date: 2005/02/02 Wed PM 06:10:51 EST
> To: mathgroup at smc.vnet.net
> Subject: [mg53913] [mg53907] Problem with matching.
> 
> Can someone tell me why this doesn't match?
> 
> F[{x, 2, c}]F[{x, 1, f}] /. F[{___, a_, ___}]F[{___, a_, ___}] :> yes
> 
> I'm expecting 'yes' to be returned if any of the list arguments to F[]
> contain the same value.  It doesn't match however; what am I doing
> wrong?
> 
> Thanks,
> Joe
> --
> Josef Karthauser (joe at tao.org.uk)	       http://www.josef-k.net/
> FreeBSD (cvs meister, admin and hacker)     http://www.uk.FreeBSD.org/
> Physics Particle Theory (student)   http://www.pact.cpes.sussex.ac.uk/
> ================ An eclectic mix of fact and theory. 
=================
> 
> 
> 


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