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LOGICAL FUNCTION VISII (X,Y, XA,YA, XB,YB, XC,YC, XD,YD)
C$ (Interpolate Intersection)
C$ Given two line segments (XA,YA)..(XB,YB) and
C$ (XC,YC)..(XD,YD), return .TRUE. if they intersect between
C$ their endpoints, and .FALSE. otherwise. If they intersect
C$ anywhere, (X,Y) is set to the point of intersection. In
C$ order to deal with floating-point roundoff problems, the
C$ line segments are extended by a small amount in determining
C$ whether the computed intersection point lies on them.
C$ Otherwise, they are parallel and (X,Y) is arbitrarily set
C$ to (XA,YA) so that the output is always defined.
C$ (30-NOV-83)