Re: Notation Question
- To: mathgroup at smc.vnet.net
- Subject: [mg47550] Re: Notation Question
- From: Paul Abbott <paul at physics.uwa.edu.au>
- Date: Thu, 15 Apr 2004 05:02:16 -0400 (EDT)
- Organization: The University of Western Australia
- References: <c5lfds$bqh$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
In article <c5lfds$bqh$1 at smc.vnet.net>,
scohen at cable.net.co (Sebastian Cohen S) wrote:
> I need to make Mathematica understand that:
>
> Subscript[X,j] for j = 3
>
> for example is Part[X,3] and more generally to understand that:
>
> the input should internally handle Subscript[exp, i,j]
> as Part[exp, i,j]
If
x = {{a,b},{c,d},{e,f}};
then
Subscript[x,j__] := x[[j]]
does what you want.
Note that you can use a subscripted form of indexing using [[ ]]
_without_ any definitions. For example, if paste the following into a
Notebook,
Cell[BoxData[SubscriptBox["x", RowBox[{"\[LeftDoubleBracket]", "3",
"\[RightDoubleBracket]"}]]], "Input"]
and then evaluate it. This automatically works in the general case.
Cheers,
Paul
--
Paul Abbott Phone: +61 8 9380 2734
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