Dear GAP-Forum,

George McNinch wrote:

GAP4, Version: 4r2 of 29-Feb-2000, i686-pc-linux-gnu-gcc

gap> R := Integers mod 9;
(Integers mod 9)
gap> S := FullMatrixAlgebra(R,2);
( (Integers mod 9)^[ 2, 2 ] )
gap> Units(S);
Segmentation fault

A crash certainly is a bug. As noted already, this bug has been corrected
in one of the bugfixes for GAP4R2.

However (as also noted) now GAP 4.2 will stop with an error message (``No
method found'') that indicates that the capability to test invertibility of a
matrix in this ring has not been implemented.

(The forthcoming release 4.3 will be able to calculate the units in this
example.)

Best wishes,

Alexander Hulpke

-- Colorado State University, Department of Mathematics,
Weber Building, Fort Collins, CO 80523, USA
email: hulpke@math.colostate.edu, Phone: ++1-970-4914288
http://www.math.colostate.edu/~hulpke