Re: Pattern Matching Problem
- To: mathgroup at smc.vnet.net
- Subject: [mg43416] Re: Pattern Matching Problem
- From: bghiggins at ucdavis.edu (Brian Higgins)
- Date: Fri, 29 Aug 2003 07:16:31 -0400 (EDT)
- References: <bihp1v$b3u$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Ted, Here is a kludge approach:
Flatten[{DeleteCases[expr, f[_, _], Infinity],
Apply[Plus, Split[Sort[Cases[expr, f[_, _], Infinity], #2[[2]] >
#1[[2]] & ], #1[[2]] == #2[[2]] & ], 1]}]
Cheers,
Brian
"Ersek, Ted R" <ErsekTR at navair.navy.mil> wrote in message news:<bihp1v$b3u$1 at smc.vnet.net>...
> 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]}
>
> 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