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Topic: Subscript on plus expression
Replies: 16   Last Post: Dec 3, 2012 3:18 AM

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Dave Snead

Posts: 52
Registered: 12/13/04
Re: Subscript on plus expression
Posted: Nov 19, 2012 5:05 PM
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Nasser --,

I'm using these as tensor indices.

Although Bob Hanlon offered a workaround (thanks Bob)
Format[Subscript[arg_Plus, k_]] :=
Subscript["(" <> StringJoin @@
Riffle[ToString /@ (List @@ arg),
" + "] <> ")", k]
Subscript[a + b + 2, k],

I think the folks at Mathematica should fix this and insert the parentheses.
The output of Subscript[Plus[a,b],k] should not be represented as

-- Dave

-----Original Message-----
From: Nasser M. Abbasi
Sent: Sunday, November 18, 2012 2:13 PM
Subject: Re: Subscript on plus expression

On 11/18/2012 3:03 AM, Dave Snead wrote:
> Hi,
> Mathematica fails to parenthesize the a+b in
> Subscript[Plus[a,b],k]
> so the output looks identical to
> Plus[a,Subscript[b,k]]
> Is this a bug?
> Is there an option to force the parentheses?
> Thanks in advance,
> Dave Snead

Actually, just typing


and then hitting ENTER will result in


i.e. the () are gone. Same effect you showed.

It might be because subscript are meant to be applied to an atomic symbol
and not combined expression like a+b. I do not know. I am not even sure
what (a+b)_k is supposed to mean, math wise. Is this meant to
be on the code or in a text cell? If it is in the code itself,
how will it be used?


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