## CGAL::Ray_2<Kernel>

### Definition

An object r of the data type Ray_2<Kernel> is a directed straight ray in the two-dimensional Euclidean plane 2. It starts in a point called the source of r and goes to infinity.

### Creation

 Ray_2 r ( Point_2 p, Point_2 q); introduces a ray r with source p and passing through point q. Ray_2 r ( Point_2 p, Direction_2 d); introduces a ray r starting at source p with direction d. Ray_2 r ( Point_2 p, Vector_2 v); introduces a ray r starting at source p with the direction of v. Ray_2 r ( Point_2 p, Line_2 l); introduces a ray r starting at source p with the same direction as l.

### Operations

bool r.operator== ( h) const Test for equality: two rays are equal, iff they have the same source and the same direction.

bool r.operator!= ( h) const Test for inequality.

Point_2<Kernel> r.source () const returns the source of r.

Point_2<Kernel> r.point ( int i) const returns a point on r. point(0) is the source, point(i), with i>0, is different from the source.
 Precondition: i ≥ 0.

Direction_2<Kernel> r.direction () const returns the direction of r.

Vector_2<Kernel> r.to_vector () const returns a vector giving the direction of r.

Line_2<Kernel> r.supporting_line () const returns the line supporting r which has the same direction.

Ray_2<Kernel> r.opposite () const returns the ray with the same source and the opposite direction.

### Predicates

bool r.is_degenerate () const ray r is degenerate, if the source and the second defining point fall together (that is if the direction is degenerate).

bool r.is_horizontal () const
bool r.is_vertical () const

bool r.has_on ( Point_2<Kernel> p) const
A point is on r, iff it is equal to the source of r, or if it is in the interior of r.

bool r.collinear_has_on ( Point_2<Kernel> p) const
checks if point p is on r. This function is faster than function has_on() if the precondition checking is disabled.
 Precondition: p is on the supporting line of r.

### Miscellaneous

 Ray_2 r.transform ( Aff_transformation_2 t) const returns the ray obtained by applying t on the source and on the direction of r.