is
Tests if line between Point pair is degenerate.
Line with no length or that moves a very short distance is degenerate; it is treated as a point.
exact changes the equality test. If true, returns true only if p1 equals p2. If false, returns true if p1 equals or nearly equals p2.
Return
true if line is degenerate; its length is effectively zero
Parameters
p1
line start point
p2
line end point
exact
if false, allow nearly equals