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RE: PatternMatching with Dt[]

• To: mathgroup at smc.vnet.net
• Subject: [mg37300] RE: [mg37264] PatternMatching with Dt[]
• From: "David Park" <djmp at earthlink.net>
• Date: Tue, 22 Oct 2002 04:47:40 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Johannes,

You need to use HoldPattern to prevent the lhs of the rule from being
evaluated.

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

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/

From: Johannes Ludsteck
To: mathgroup at smc.vnet.net
[mailto:johannes.ludsteck at wiwi.uni-regensburg.de]

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