 
introduces the direction d of vector v.
 
 
introduces the direction d of line l.
 
 
introduces the direction d of ray r.
 
 
introduces the direction d of segment s.
 
 
introduces a direction d passing through the origin
and the point with Cartesian coordinates (x, y).



returns values, such that d== Direction_2<Kernel>(delta(0),delta(1)).
 

 returns delta(0).  

 returns delta(1). 
There is a total order on directions. We compare the angles between the positive xaxis and the directions in counterclockwise order.

















Furthermore, we have

 
returns true, iff d is not equal to d1, and while rotating counterclockwise starting at d1, d is reached strictly before d2 is reached. Note that true is returned if d1 == d2, unless also d == d1.  

 The direction opposite to d. 

 returns a vector that has the same direction as d. 

 
returns the direction obtained by applying t on d. 