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Re: Re: Question about Hold

• To: mathgroup at smc.vnet.net
• Subject: [mg48862] Re: [mg48826] Re: Question about Hold
• From: Daohua Song <ds2081 at columbia.edu>
• Date: Sat, 19 Jun 2004 04:31:27 -0400 (EDT)
• References: <carjrn$r76$1@smc.vnet.net> <200406180612.CAA10664@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Hi,Steve...
    Thanks for all your help, also sorry for some uncertainty about the 
questions.in fact the questions is quite straightforward:
    e.g i define Commute[A,B]=C (all operators), how to let mathematica 
knows Commute[A^2,B]=AC+CA.
    I figure out one solutions later.

\!\(\*
   RowBox[{
     RowBox[{\(Commute[a_\^n_Integer, b_] /; n > 1\), ":=",
       RowBox[{
         RowBox[{"(",
           RowBox[{"Commute", "[",
             RowBox[{
               RowBox[{"Times", "@@",
                 RowBox[{"Table", "[",
                   StyleBox[\(SubscriptBox[a, i], {i, n}\),
                     "MR"], "]"}]}],
              ",", "b"}], "]"}], ")"}], "/.", \(SubscriptBox[
               a, _] :> a\)}]}], ";"}]\)

kinda of foolish:).
Jens give a simple solution, altough (Commute[a,b]=ab-ba)
Commute[a^n_, b] := AntiCommute[a^(n - 1), Commute[a, b]]

• References:
  • Re: Question about Hold
    • From: "Steve Luttrell" <steve_usenet@_removemefirst_luttrell.org.uk>