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[MUG] Re: Maple problem (?)
| [MUG] Re: Maple problem (?) |
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Author: Maple User Group
Posted: Fri, 9 Aug 2002 17:55:51 -0400 (
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>> From: Maple User Group "maple_gr"
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Date: Thu, 8 Aug 2002 08:37:39 +1000
To: "maple-list"
From: "W.Whiten" (Bill Whiten)
Subject: Maple problem (?)
Paul,
D[n] refers to nth argument, not nth derivative e.g.:
> D[1](exp);
exp
> D[1](x->x^2);
x -> 2 x
> D[2]](exp);
Error, (in D/exp) invalid arguments
> D[2](x->x^2);
Error, (in D/procedure) index out of range: function takes only 1 arguments
> D[1]((x,y)->x^2+y^2);
(x, y) -> 2 x
> D[2]((x,y)->x^2+y^2);
(x, y) -> 2 y
>
> D[1](D[1](exp));
exp
> D[1](D[2]((x,y)->x^2*y^2));
(x, y) -> 4 x y
>
Regards,
>>> From: "Paul E.S. Wormer" "pwormer"
>Here follows a transcript of a Maple 6 session on a PC:
>
>-----------------------------------------------------------
>> restart;
>> D[1](f); D[2](f);
>
> D[1](f)
>
>
> D[2](f)
>
>> D[1](exp@f);
>
> (exp@f) D[1](f)
>
>> D[2](exp@f);
>Error, (in D/exp) invalid arguments
>------------------------------------------------------------
>
>My question is: what is wrong with the last statement?
>
>Thank you in advance for an answer,
-----------
Bill Whiten, "W.Whiten"
Julius Kruttschnitt Mineral Research Centre,
The University Of Queensland, Tel: int +61 7 3365 5888
Isles Rd, Indooroopilly, Fax: int +61 7 3365 5999
Brisbane Qld 4068, AUSTRALIA.
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Date: Wed, 7 Aug 2002 17:16:57 -0700 (PDT)
From: Robert Israel "israel"
To: "maple-list"
Subject: Maple problem (?)
It's a bug, and still present in Maple 8.
A work-around is
> g:= (s,t) -> exp(f(s,t));
D[2](g);
Robert Israel "israel"
Department of Mathematics http://www.math.ubc.ca/~israel
University of British Columbia
Vancouver, BC, Canada V6T 1Z2
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From: Stanley J Houghton "S.J.Houghton"
Date: Fri, 9 Aug 2002 09:40:28 +0100
To: "maple-list" "pwormer"
Subject: Maple problem (?)
Paul
It looks to me like a bug arising from
> D[2](f@g);
(D[2](f)@g)*D[2](g)
Surely, by definition, it should deliver the result (D[1](f)@g)*D[2](g)
when f is a function of one variable (as with exp in your case).
In addition, I see that the same error arises when the variables are
explicitly shown in
> D[2]((x,y)->(exp@f)(x,y));
I await comment from others.
Regards
Stan
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