Re: Pattern Matching Problem
- To: mathgroup at smc.vnet.net
- Subject: [mg43394] Re: Pattern Matching Problem
- From: bobhanlon at aol.com (Bob Hanlon)
- Date: Fri, 29 Aug 2003 07:15:54 -0400 (EDT)
- References: <bihp1v$b3u$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
I would take a different approach:
ClearAll[f,a,b,c,w,x,y,z,sep];
sep[expr_] := Module[
{tm = List@@expr, at},
at = Select[tm,AtomQ];
Tr/@Prepend[
Split[
Sort[Complement[tm,at],
#1[[2]]<#2[[2]]&],
#1[[2]]==#2[[2]]&],
at]];
expr=a+b+c+f[w,2]+f[w,3]+x+f[x,2]+f[x,3]+y+f[y,2]+f[z,2];
sep[expr]
{a + b + c + x + y, f[w, 2] + f[x, 2] + f[y, 2] + f[z, 2],
f[w, 3] + f[x, 3]}
Bob Hanlon
In article <bihp1v$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]}
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.