Re: representing the dihedral group {1,r,r^2...s,sr^2...}
- To: mathgroup at smc.vnet.net
- Subject: [mg98861] Re: representing the dihedral group {1,r,r^2...s,sr^2...}
- From: dh <dh at metrohm.com>
- Date: Mon, 20 Apr 2009 19:09:44 -0400 (EDT)
- References: <gsh100$gr$1@smc.vnet.net>
Hi,
it calls for troubles changing the rules for built in functions. Instead
assigne the rule to your symbols. E.g.:
s /: s^2 = 1;
s /: s^n_ := s s^(n - 1) /. n > 2;
r /: r^4 = 1;
r /: r^n_ := r r^(n - 1) /; n > 4;
Daniel
obott0 at gmail.com wrote:
> Hi, I'm trying to represent the dihedral group {1,r,r^2...s,sr^2...}
> in mathematica so I can do for example:
>
> s^3
>
> and get s.
>
> I tried this code:
>
> Unprotect[Times, Power];
> n = 4;
> ClearAll[r, s, Times, Power];
> SetAttributes[Times, {Flat}]
> s^2 = 1;
> r^n = 1;
> Protect[Times, Power];
>
> But this doesn't work for, for example, s^3. It is not able to
> simplify it.
>
> Thanks a lot!
>
> Otto
>