% This example, from Shigetoshi Katsura <katsura@juna.j.dendai.ac.jp>,
% generates a catastrophic error, presumably because a careful enough
% check of the non-commutative division is not maintained in the matrix
% code.

operator a;

noncom a;

m := mat((a(x),a(y)),(a(z),a(w)));

m**(-1);
     
end;
