Position of a point and a straight line or segment

Position determines the relative position of a planar point C with respect to
a planar segment joining A and B. This is not intended for 3D points.
Pos=0 =>the point C is collinear with A and B
Pos=1=>the point C is above the segment
Pos=-1=>the point C is below the segment
Example
A=[0 0 0]; B=[1 1 0]; C=[1 0 0];
Pos=Position(B,A,C)

Since C is below AB then Pos=-1
Note: in case of 2D points, you still have to include the z-ordinate, i.e
if you have a point S=[1 2], add a zero to get S=[1 2 0], and use the same
procedure as the above example