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mma and finite fields

  • To: mathgroup at
  • Subject: mma and finite fields
  • From: fairman at (Fairman)
  • Date: 24 Aug 93 19:38:43 GMT

I've been trying to get mathematica deal with finite fields by using
ff[] to indicate that the argument to ff[] is an element of a
particular finite field. So, I'm not using ff[] as a function; it's
being used as a way to signal a variable (or expression) of a
particular type.

Suppose the field is GF(2^{2m+1}), so that whenever ff[a] occurs, we
know that a is an element of GF(2^{2m+1}). What I've tried to do is
define certain rules for ff[]. For instance,

ff[0] := 0;
ff[2 x_] := 0;
ff[x_ + y_] := ff[x] + ff[y];
ff[x_] ff[y_] := ff[x y];
x_ ff[y_] := ff[x y];
ff[x_]^y_ := ff[x^y];

and so forth. Note that to make these definitions, Power and Times had
to be Unprotect[]-ed. I also need some means of reducing exponents
modulo 2m+1. I haven't been able to get this idea to work.
Ideas, anyone? I'm not interested in doing calculations involving
particular elements of GF(q), rather in working with equations, where
the variables are known to lie in GF(q).

Randall Fairman
fairman at

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