86.8 IsLowerTriangularMat

IsLowerTriangularMat( mat )

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

    gap> a := [ [ 1, 2 ], [ 3, 1 ] ];;
    gap> IsLowerTriangularMat( a );
    false
    gap> a[1][2] := 0;;
    gap> IsLowerTriangularMat( a );
    true 

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