Sure so I recently was doing point of intersection of 2 line segments.
in this case, we have a line that has the same Y value at both endpoints. So one might want to ensure that a given point of intersection is:
A.y <= PoI.y <= B.y
So say A.y = 1.5000000000001 and B.y = 1.4999999999999999 and PoI.y = 1.5
It will fail the check!
but, A.y <≈ PoI.y <≈ B.y
would work just fine.
Does that make sense? Sorry if this is still unclear.