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MathGroup Archive 2002

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RE: PatternMatching with Dt[]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg37301] RE: [mg37264] PatternMatching with Dt[]
  • From: "DrBob" <drbob at bigfoot.com>
  • Date: Tue, 22 Oct 2002 04:47:43 -0400 (EDT)
  • Reply-to: <drbob at bigfoot.com>
  • Sender: owner-wri-mathgroup at wolfram.com

This works:

Dt[x] /. HoldPattern@Dt[arg_] -> f[arg]

The problem apparently is this:

In[7]:=Dt[x_]
Out[7]=Dt[x]*Derivative[1, 0][Pattern][x, _]

That seems odd to me, and I'm not sure why Unevaluated doesn't help.

DrBob

-----Original Message-----
From: Johannes Ludsteck
To: mathgroup at smc.vnet.net
[mailto:johannes.ludsteck at wiwi.uni-regensburg.de] 
Subject: [mg37301] [mg37264] PatternMatching with Dt[]


I would like to replace Dt[x_] in a complex 
expression. For example consider

Dt[x]/.Dt[arg_]->f[arg]

where x is a pure Symbol (has no value).
However, Mathematica refuses apply the rule.
Various other attempts, for example 
Unevaluted[Dt[arg_]]:>f[arg]
and HoldForm[...] were unsuccessful.

I managed to  circumvent the problem by
Dt[x]/.Dt->fun
However, I were more happy if I understood why the 
first attempt was not successful.
Can someone explain?

Best regards,
	Johannes Ludsteck
<><><><><><><><><><><><>
Johannes Ludsteck
Economics Department
University of Regensburg
Universitaetsstrasse 31
93053 Regensburg
Phone +49/0941/943-2741






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