86.7 IsDiagonalMat

IsDiagonalMat( mat )

mat must be a matrix. This function returns true if all entries mat[i][j] with i<j are equal to 0*mat[i][j] and false otherwise.

    gap> a := [ [ 1, 2 ], [ 3, 1 ] ];;
    gap> IsDiagonalMat( a );
    false