One way to advance the science of computational geometry is
to make a comprehensive study of fundamental operations that
are used in many different algorithms. This monograph
attempts such an investigation in the case of two basic
predicates: the counterclockwise relation pqr, which states
that the circle through points (p, q, r) is traversed
counterclockwise when we encounter the points in cyclic
order p, q, r, p,...; and the incircle relation pqrs, which
states that s lies inside that circle if pqr is true, or
outside that circle if pqr is false. The author, Donald
Knuth, is one of the greatest computer scientists of our
time. A few years ago, he and some of his students were
looking at amap that pinpointed the locations of about 100
cities. They asked, "Which ofthese cities are neighbors of
each other?" They knew intuitively that some pairs of cities
were neighbors and some were not; they wanted to find a
formal mathematical characterization that would match their
intuition.This monograph is the result.