test if point is left of line code example

Example: check if point is left or right of vector

Check position of point M(X, Y) relative to vector AB with points A(Ax, Ay) and B(Bx, By):

position = sign((Bx - Ax) * (Y - Ay) - (By - Ay) * (X - Ax))

M is: 	+1 left,
		-1 right,
    	0 on the vector AB