internal static extern IntPtr RHC_RhinoExtendCurve1(IntPtr pConstCurve, ExtendCurveConsts type, int side, IntPtr pGeometryList);
 internal static extern IntPtr RHC_RhinoExtendCurve2(IntPtr pConstCurve, ExtendCurveConsts type, int side, Point3d endPoint);
 internal static extern IntPtr RHC_RhinoExtendCurve(IntPtr pConstCurve, double length0, double length1, ExtendCurveConsts type);