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From: trh@ukc.UUCP
Newsgroups: net.math.symbolic
Subject: Help with MACSYMA problem
Message-ID: <5235@ukc.UUCP>
Date: Tue, 18-Jun-85 19:48:09 EDT
Article-I.D.: ukc.5235
Posted: Tue Jun 18 19:48:09 1985
Date-Received: Fri, 14-Jun-85 05:06:05 EDT
Distribution: net
Organization: Computing Laboratory, U of Kent at Canterbury, UK
Lines: 35

On computing some large expressions via Macsyma the following statements

	dn : diff(n,t);
	dn0 : ev(dn, t=0);

produce a `can't differentiate w.r.t a number 0 ' message.

Looking at n it contains some

	expt( long boring expression, <-1>)

messages in it, dn then contains

	d
	- expt( long boring expression, -1)
	dt

and hence the catastrophe.

I've tried all ( well it seems like it!) combinations of simp, expand, diff
and eval in ev but I can't get rid of the expt.

Please can somebody help.


Tim Hopkins,
Computing Laboratory,
University of Kent,
Canterbury CT2 7NF
Kent
U.K.

{ trh@ukc.UUCP 
  trh%ukc@ucl-cs.ARPA
  na.hopkins@su-score.ARPA }