PrintArray( mat )
PrintArray displays the matrix mat in a pretty way.
gap> m := [[1,2,3,4],[5,6,7,8],[9,10,11,12]];
[ [ 1, 2, 3, 4 ], [ 5, 6, 7, 8 ], [ 9, 10, 11, 12 ] ]
gap> PrintArray( m );
[ [ 1, 2, 3, 4 ],
[ 5, 6, 7, 8 ],
[ 9, 10, 11, 12 ] ]
GAP 3.4.4