This abstract method must be overridden. He returns the first deriavation of the function defined in the method Value. All parameter t are taken from the interval [fromParam,toParam].
This method calculates the distance of a LineType to a Curve only in case, when the distance is smaller then MaxDist else big will be returned. You can imagine a cylinders with radius MaxDist around the Curve. If now the line goes through the "curved" cylinder, then this is a good one and the distance will be calculated and returned.
This method trims the curve to the part bewtween from and to. The base-method sets fromParam = from and toParam = to. In general this is not the best solution. So it is better to override this method without call to the basemethod.
Transforms a Curve with the transformation given by m. The method in the baseclass is empty. So you have to override this function, if you want to transform a Curve.