Re: Telling Mathematica that a symbol is going to be a List?
- To: mathgroup at smc.vnet.net
- Subject: [mg50829] Re: Telling Mathematica that a symbol is going to be a List?
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Wed, 22 Sep 2004 04:52:09 -0400 (EDT)
- Organization: Universitaet Leipzig
- References: <ciqvop$in9$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
m = Hold[{{d[[1]], 0, 0}, {0, d[[2]], 0}, {0, 0, d[[3]]}}];
m /. {d -> {d1, d2, d3}} // ReleaseHold
Regards
Jens
AES/newspost wrote:
>
> I want to define a function containing parameters that are going to be
> elements in a list, e.g. something like
>
> m := { { d[[1]], 0, 0}, {0, d[[2]], 0}, {0, 0, d[[3]]}
>
> but not define the list of values of d until later (and not put the
> parameters in as explicit arguments of m just to keep the appearance
> less cluttered and typing easier).
>
> If I then give an input line
>
> m /. {d -> {d1, d2, d3} } // MatrixForm
>
> I get "Part::partd" errors -- but the matrix then displays correctly.
>
> I can of course just Off[] the errors -- but is there a better way.