Re: Almost symbolic computations (?)
- To: mathgroup at smc.vnet.net
- Subject: [mg90510] Re: Almost symbolic computations (?)
- From: David Bailey <dave at Remove_Thisdbailey.co.uk>
- Date: Fri, 11 Jul 2008 02:04:22 -0400 (EDT)
- References: <g54oim$etu$1@smc.vnet.net>
Barbara Da Vinci wrote:
> Dear MathGroup
>
> This is an example of the problem
> I'm facing.
>
> The code
>
> Needs["VectorAnalysis`"];
> Head /@ {ax, ay, az}
> A = {ax, ay, az};
> Curl[A]
>
> returns
>
> {Symbol, Symbol, Symbol}
> {0, 0, 0}
>
> Instead, I would get the
> well known symbolic form
>
> d_y az - d_z ay
> ...
>
> I have been trying, for
> a while, to perform string
> manipulations but that,
> of course, lays to ashes
> the possibility to recognize
>
> d_y az + d_y az = 2 d_y az
>
> and so on.
>
> Any way to get out of it ?
>
> Kind regards
>
>
> Barbara Da Vinci
>
Possibly part of the confusion here is that ax (with no space) is a
variable with a two-letter name, whereas a x (with a space) is a product
of a with x.
David Bailey
http://www.dbaileyconsultancy.co.uk