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MathGroup Archive 2005

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Re: named pattern variable scoped as global, should be local

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56736] Re: named pattern variable scoped as global, should be local
  • From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
  • Date: Thu, 5 May 2005 06:01:19 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <d59kg5$6ch$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

and what does
x = 7;
Module[{x}, {1, 2, 3} /. x_ :> 2x]

and

x = 7;
Block[{x}, {1, 2, 3} /. x_ -> 2x]

Regards

  Jens




<leenewman at gmail.com> schrieb im Newsbeitrag 
news:d59kg5$6ch$1 at smc.vnet.net...
> When using a named pattern variable within a 
> module, it should be
> scoped locally within the pattern.  However, 
> this does not seem to work
> as advertised.  For example, shouldn't the 
> pattern variable x in the
> statements below be local to the pattern?  Does 
> anyone know whether
> this is a bug, or whether I am just missing 
> something about the usage
> of variables in patterns/condition constructs?
>
> (* this returns 14! *)
> x = 7;
> Module[{x},{1, 2, 3} /. x_ -> 2x];
>
> (* this returns {2,4,6}, assuming q is not 
> globally defined. *)
> Remove[q];
> Module[{q},{1, 2, 3} /. q_ -> 2q];
>
>
> Lee
> 



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