Re: Matrices-in-functions question
- To: mathgroup at smc.vnet.net
- Subject: [mg20462] Re: Matrices-in-functions question
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Wed, 27 Oct 1999 02:04:37 -0400
- Organization: Universitaet Leipzig
- References: <7v3c1t$5uh@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
you must prevent that Part[mat,__] is evaluatet for symbols.
Define:
z[mat_?MatrixQ] := mat[[1, 1]] a + mat[[1, 2]]
and
z[mat] /. mat -> {{1, 2}, {3, 4}}
will do what you want.
Regards
Jens
Aram Schiffman wrote:
>
> Here is a simple one, but I can't work it out.
>
> I would like to be able to define a function this way:
>
> z=mat[[1]][[1]] a + mat[[1]][[2]]
>
> without specifying what "mat" is explicitly. I would evaluate it later this
> way:
>
> z/.mat->somePredefinedMatrix
>
> Of course, Mathematica complains about the definition (Part specification mat[[1]] is
> longer than depth of object) ... is there a way to make this fly?
>
> Thanks,
> Aram Schiffman