       Re: Pattern Matching Problem

• To: mathgroup at smc.vnet.net
• Subject: [mg43389] Re: Pattern Matching Problem
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Tue, 16 Sep 2003 04:35:39 -0400 (EDT)
• Organization: Universitaet Leipzig
• References: <bihp1v\$b3u\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

you mean

or

{Select[#, Symbol === Head[#] &], Select[#, f === Head[#] &]} & [expr]

or

Plus @@@ {Cases[#, _Symbol], Cases[#, _f]} & [expr]

or

(lst = Cases[#, _.*_f]; {# - Plus @@ lst, Plus @@ lst}) & [expr]

or

{DeleteCases[#, _.*_f], Cases[#, _.*_f]} &[expr]

?

Regards
Jens

"Ersek, Ted R" wrote:
>
> Consider the following:
>
> In:=
>   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]}
>
> The pattern matcher should be able to do this because Plus has attributes
> Flat and Orderless.  However I can't find a way to make it happen.
>
> -------------------
> Thanks,
>    Ted Ersek

```

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