The function can set the values for:
sub parameter: small value that is used in mixture quantile function
to test if the computed value is infimum, default: 1e-10.
add parameter: small value that is added to values that are in the image of CDF in qlim
function, default: 1e-08.
tol parameter: tolerance for uniroot used in mixture quantile function, default: .Machine$double.eps^0.5.