On Thu, 23 Sep 1999, Sergei Haller wrote:

r:=Rationals;
vars:=[];
a:=Indeterminate(r, "a", vars);Add(vars, last);

m:=[[1,a],[0,1]]; # for example

... Inverse(m) or m^-1 (and all operations like m/m, which require m^-1)
don't work
But [[1,a],[0,1]]*[[1,-a],[0,1]] returns [[1,0],[0,1]]

I have success if I define m as follows:

gap> m:=[[a^0,a],[0*a,a^0]];
[ [ 1, a ], [ 0, 1 ] ]
gap> IsOrdinaryMatrix(m); # Now all matrix elements are from the same Family
true
gap> m^-1;
[ [ 1, -a ], [ 0, 1 ] ]
gap>

But this seems to be too complicate to do this. As said befroe,
multiplication, addition and subtraction work with m:=[[1,a],[0,1]] also.

Now is my Question: Is this the common way to define such matrices?
Is there any other way?

Thank you in advance.

c ya
        Sergei

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