[Q] Extracting patterns

*To*: mathgroup at smc.vnet.net*Subject*: [mg18607] [Q] Extracting patterns*From*: "Kevin Jaffe" <kj0 at mailcity.com>*Date*: Tue, 13 Jul 1999 01:01:32 -0400*Organization*: MailCity (http://www.mailcity.lycos.com:80)*Sender*: owner-wri-mathgroup at wolfram.com

How can I extract the first argument of expressions having the form Pattern[x, y]? I know how to do something like this in other situations, e.g.: In[1]:= Plus[x, y] /. Plus[a_, b_] -> a Out[1]= x But this strategy fails when the head of the lhs expression is Pattern: In[2]:= Pattern[x, y] /. Pattern[a_, b_] -> a Pattern::patsym: First element in pattern Pattern[a_, b_] is not a symbol. Out[2]= x:y In a last-gasp effort, I also tried: In[3]:= Pattern[x, y] /. HoldPattern[Pattern[a_, b_]] -> a Pattern::patsym: First element in pattern Pattern[a_, b_] is not a symbol. Out[3]= x:y to no avail. Is there a way to do this? Thanks, kj0 at mailcity.com Get your FREE Email at http://mailcity.lycos.com Get your PERSONALIZED START PAGE at http://my.lycos.com

**Follow-Ups**:**Re: [Q] Extracting patterns***From:*"Wolf, Hartmut" <hwolf@debis.com>