Re: Pattern Matching Problem

• To: mathgroup at smc.vnet.net
• Subject: [mg43415] Re: Pattern Matching Problem
• From: Paul Abbott <paul at physics.uwa.edu.au>
• Date: Tue, 16 Sep 2003 04:36:32 -0400 (EDT)
• Organization: The University of Western Australia
• References: <bihp1v\$b3u\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```In article <bihp1v\$b3u\$1 at smc.vnet.net>,
"Ersek, Ted R" <ErsekTR at navair.navy.mil> wrote:

> Consider the following:
>
> In[1]:=
>   ClearAll[f,a,b,c,w,x,y,z];
>   expr=a+b+c+f[w,2]+f[w,3]+x+f[x,2]+f[x,3]+y+f[y,2]+f[z,2];
>
>
> Can somebody suggest a general way to seperate the terms above into like
> groups. By "like" I mean having the same second argument for (f).  So for
> this example I want to get
>
> {a+b+c+x+y,  f[w,2]+f[x,2]+f[y,2]+f[z,2],   f[w,3]+f[x,3]}

Not a full answer to your question, but one can get the partitioning you
are after using

Collect[expr /. c:f[_, n_] :> g[n] c, g[_]]

Cheers,
Paul

--
Paul Abbott                                   Phone: +61 8 9380 2734
School of Physics, M013                         Fax: +61 8 9380 1014
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Crawley WA 6009                      mailto:paul at physics.uwa.edu.au
AUSTRALIA                            http://physics.uwa.edu.au/~paul

```

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