This version of Sign returns +1 if the points are definitely CCW, -1 if
they are definitely CW, and 0 if two points are identical or the result
is uncertain. Uncertain cases can be resolved, if desired, by calling
ExpensiveSign.
The purpose of this method is to allow additional cheap tests to be done,
where possible, in order to avoid calling ExpensiveSign unnecessarily.
This version of Sign returns +1 if the points are definitely CCW, -1 if they are definitely CW, and 0 if two points are identical or the result is uncertain. Uncertain cases can be resolved, if desired, by calling ExpensiveSign.
The purpose of this method is to allow additional cheap tests to be done, where possible, in order to avoid calling ExpensiveSign unnecessarily.