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Re: Notation Question


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

-- 
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