ABSTRACT
Let us fix a ray R. with the origin at a point 0. This ray is called a vertical ray. Given a polygonal line g and a straight line (or ray) I, a point P where g is intersected by l is called a proper intersection point if P is not a vertex of g or if P is a vertex of g such that two edges adjoining P are situated on a different half-plane with respect to 1. We construct some special function N(Q,g) in the following manner. Consider a ray RQ collinear to R. with the origin at a point Q; if the number of points where RQ intersects g properly is even, we set N(Q,g) = 0. If not, we set N Q , g ) = 1.
