The last output line of the following code -which I took from your article and just replaced the 'mysum' function with 'sum' in- returns 'false' :
am:lambda([i,j],a[i,j])$
bm:lambda([i,j],b[i,j])$
unitm:lambda([i,j],k_delta(i,j));
matmul(R,S):=
block([rrow:part(R,1,1),
scol:part(S,1,2),
index:?gensym()],
apply(lambda,[[rrow,scol],
sum(R(rrow,index)*S(index,scol),index,1,n)]));
is((matmul(am,unitm)-am)=0);
> -----Original Message-----
> From: fateman at cs.berkeley.edu
> Sent: Tue, 18 Mar 2008 14:42:05 -0700
> To: shahir at inbox.com
> Subject: RE: [Maxima] Matrices of indefinite size
>
> I looked through that article. What did you try that did not work in
> Maxima?
> RJF