is_tril

is_tril(matrix: any[] | Mat) : boolean

param matrix - Any matrix, must be 2 dimensional and square, to test if it's lower triangular or not

returns: boolean - true if it is lower triangular, false otherwise.

This function tests if a square 2-D matrix is lower triangular or not. Lower triangular matrices have the property that above the diagonal, all values are zero. Thus one can look at the diagonal and see if theres any entry above the diagonal that is non zero. If there is, it is not lower triangular.