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Re: Question on pattern matching

• To: mathgroup at smc.vnet.net
• Subject: [mg47791] Re: Question on pattern matching
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Tue, 27 Apr 2004 04:46:35 -0400 (EDT)
• Organization: Universitaet Leipzig
• References: <c6ibik$6fp$1@smc.vnet.net>
• Reply-to: kuska at informatik.uni-leipzig.de
• Sender: owner-wri-mathgroup at wolfram.com

Hi,

Orderless mean not that Mathematica try all possible argument
orderings, it mean that Mathematica can order the arguments in the
way it likes it (OrderedQ[args]===True)

Regards
  Jens

Roman Green wrote:
> 
> Hi,
> 
> I am a very newbie in Mathematica so sorry for possibly stupid question.
> 
> In the following Mathematica's output
> In[1]:= SetAttributes[k, Orderless]
> In[2]:= k[a, b, b] /. k[x_, x_, y_] -> 0
> Out[2]= 0
> In[3]:= k[a, b, b] /. k_[x_, x_, y_] -> 0
> Out[3]= k[a, b, b]
> 
> I can't understand why Mathematica can find match when applying pattern
> k[x_, x_, y_], but is unable with more general pattern k_[x_, x_, y_].
> 
> Thanks in advance.
> 
> ---
> 
> R. Green