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]]

```

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