GM_OrientableCurve consists of a curve and an orientation inherited from GM_OrientablePrimitive. If the orientation is "+", then the GM_OrientableCurve is a GM_Curve. If the orientation is "-", then the GM_OrientableCurve is related to another GM_Curve with a parameterization that reverses the sense of the curve traversal.<br/>GM_OrientableCurve:<br/>{Orientation = "+" implies primitive = self};<br/>{Orientation = "-" implies <br/>primitive.parameterization(length()-s) = parameterization(s)};<br/>