type Smoothness = enumeration(LinearSegments "Linear interpolation of table points", ContinuousDerivative "Akima spline interpolation of table points (such that the first derivative is continuous)", ConstantSegments "Piecewise constant interpolation of table points (the value from the previous abscissa point is returned)", MonotoneContinuousDerivative1 "Fritsch-Butland spline interpolation (such that the monotonicity is preserved and the first derivative is continuous)", MonotoneContinuousDerivative2 "Steffen spline interpolation of table points (such that the monotonicity is preserved and the first derivative is continuous)", ModifiedContinuousDerivative "Modified Akima spline interpolation of table points (such that the first derivative is continuous and shortcomings of the original Akima method are avoided)");