CircularKernel::ConstructCircularMinVertex_2

A model fo of this type must provide:

CircularKernel::Circular_arc_point_2
fo ( CircularKernel::Circular_arc_2 c)
Constructs the x-minimal vertex of c.
Precondition: The arc c is x-monotone.

CircularKernel::Circular_arc_point_2
fo ( CircularKernel::Line_arc_2 l)
Same, for a line segment.