main/src/georegression/geometry/UtilLine2D_F64.java
public static LineParametric2D_F64 convert( Point2D_F64 a , Point2D_F64 b , LineParametric2D_F64 ret )
	{
		if( ret == null )
			ret = new LineParametric2D_F64();

		ret.p.set(a);
		ret.slope.x = b.x-a.x;
		ret.slope.y = b.y-a.y;

		return ret;
	}
public static LineParametric2D_F64 convert( Point2D_F64 a , Point2D_F64 b , LineParametric2D_F64 ret )
	{
		if( ret == null )
			ret = new LineParametric2D_F64();

		ret.p.set(a);
		ret.slope.x = b.x-a.x;
		ret.slope.y = b.y-a.y;

		return ret;
	}
Converts a line segment into a line in parametric format. It will point from a to b. Point a and b must
be unique.

@param a (Input) End point of line segment
@param b (Input) End point of line segment
@param ret (output) Storage for new line.. If null a new instance will be created.
@return The resulting line