CGAL::Circle_2< Kernel > Class Template Reference

#include <CGAL/Circle_2.h>

Definition

template<typename Kernel>
class CGAL::Circle_2< Kernel >

An object c of type Circle_2 is a circle in the two-dimensional Euclidean plane \( \E^2\).

The circle is oriented, i.e. its boundary has clockwise or counterclockwise orientation. The boundary splits \( \E^2\) into a positive and a negative side, where the positive side is to the left of the boundary. The boundary also splits \( \E^2\) into a bounded and an unbounded side. Note that the circle can be degenerated, i.e. the squared radius may be zero.

Is model of

Kernel::Circle_2

Hashable if Kernel is a cartesian kernel and if Kernel::FT is Hashable

Creation
	Circle_2 (const Point_2< Kernel > &center, const Kernel::FT &squared_radius, const Orientation &ori=COUNTERCLOCKWISE)
	introduces a variable c of type Circle_2.
	Circle_2 (const Point_2< Kernel > &p, const Point_2< Kernel > &q, const Point_2< Kernel > &r)
	introduces a variable c of type Circle_2.
	Circle_2 (const Point_2< Kernel > &p, const Point_2< Kernel > &q, const Orientation &ori=COUNTERCLOCKWISE)
	introduces a variable c of type Circle_2.
	Circle_2 (const Point_2< Kernel > &center, const Orientation &ori=COUNTERCLOCKWISE)
	introduces a variable c of type Circle_2.

Access Functions
const Point_2< Kernel > &	center () const
	returns the center of c.
const Kernel::FT &	squared_radius () const
	returns the squared radius of c.
Orientation	orientation () const
	returns the orientation of c.
bool	operator== (const Circle_2< Kernel > &circle2) const
	returns true, iff c and circle2 are equal, i.e. if they have the same center, same squared radius and same orientation.
bool	operator!= (const Circle_2< Kernel > &circle2) const
	returns true, iff c and circle2 are not equal.

Predicates
bool	is_degenerate () const
	returns true, iff c is degenerate, i.e. if c has squared radius zero.
Oriented_side	oriented_side (const Point_2< Kernel > &p) const
	returns either the constant ON_ORIENTED_BOUNDARY, ON_POSITIVE_SIDE, or ON_NEGATIVE_SIDE, iff p lies on the boundary, properly on the positive side, or properly on the negative side of c, resp.
Bounded_side	bounded_side (const Point_2< Kernel > &p) const
	returns ON_BOUNDED_SIDE, ON_BOUNDARY, or ON_UNBOUNDED_SIDE iff p lies properly inside, on the boundary, or properly outside of c, resp.
bool	has_on_positive_side (const Point_2< Kernel > &p) const
bool	has_on_negative_side (const Point_2< Kernel > &p) const
bool	has_on_boundary (const Point_2< Kernel > &p) const
bool	has_on_bounded_side (const Point_2< Kernel > &p) const
bool	has_on_unbounded_side (const Point_2< Kernel > &p) const

Miscellaneous
Circle_2< Kernel >	opposite () const
	returns the circle with the same center and squared radius as c but with opposite orientation.
Circle_2< Kernel >	orthogonal_transform (Aff_transformation_2< Kernel > const &at) const
	returns the circle obtained by applying \( at\) on c.
Bbox_2	bbox () const
	returns a bounding box containing c.

Constructor & Destructor Documentation

Circle_2() [1/4]

template<typename Kernel >

CGAL::Circle_2< Kernel >::Circle_2	(	const Point_2< Kernel > &	center,
		const Kernel::FT &	squared_radius,
		const Orientation &	ori = COUNTERCLOCKWISE
	)

introduces a variable c of type Circle_2.

It is initialized to the circle with center center, squared radius squared_radius and orientation ori.

Precondition

ori != COLLINEAR and squared_radius >= 0.

Exactness

This construction is trivial and therefore always exact in Exact_predicates_inexact_constructions_kernel.

Circle_2() [2/4]

template<typename Kernel >

CGAL::Circle_2< Kernel >::Circle_2	(	const Point_2< Kernel > &	p,
		const Point_2< Kernel > &	q,
		const Point_2< Kernel > &	r
	)

introduces a variable c of type Circle_2.

It is initialized to the unique circle which passes through the points p, q and r. The orientation of the circle is the orientation of the point triple p, q, r.

Precondition

p, q, and r are not collinear.

Circle_2() [3/4]

template<typename Kernel >

CGAL::Circle_2< Kernel >::Circle_2	(	const Point_2< Kernel > &	p,
		const Point_2< Kernel > &	q,
		const Orientation &	ori = COUNTERCLOCKWISE
	)

introduces a variable c of type Circle_2.

It is initialized to the circle with diameter \( \overline{pq}\) and orientation ori.

Precondition

ori != COLLINEAR.

Circle_2() [4/4]

template<typename Kernel >

CGAL::Circle_2< Kernel >::Circle_2	(	const Point_2< Kernel > &	center,
		const Orientation &	ori = COUNTERCLOCKWISE
	)

introduces a variable c of type Circle_2.

It is initialized to the circle with center center, squared radius zero and orientation ori.

Precondition

ori != COLLINEAR.

Postcondition

c.is_degenerate() = true.

Exactness

This construction is trivial and therefore always exact in Exact_predicates_inexact_constructions_kernel.

Member Function Documentation

center()

template<typename Kernel >

const Point_2< Kernel > & CGAL::Circle_2< Kernel >::center

(

)

const

returns the center of c.

Exactness

This construction is trivial and therefore always exact in Exact_predicates_inexact_constructions_kernel.

opposite()

template<typename Kernel >

Circle_2< Kernel > CGAL::Circle_2< Kernel >::opposite

(

)

const

returns the circle with the same center and squared radius as c but with opposite orientation.

Exactness

This construction is trivial and therefore always exact in Exact_predicates_inexact_constructions_kernel.

orientation()

template<typename Kernel >

Orientation CGAL::Circle_2< Kernel >::orientation

(

)

const

returns the orientation of c.

Exactness

This construction is trivial and therefore always exact in Exact_predicates_inexact_constructions_kernel.

orthogonal_transform()

template<typename Kernel >

Circle_2< Kernel > CGAL::Circle_2< Kernel >::orthogonal_transform

(

Aff_transformation_2< Kernel > const &

at

)

const

returns the circle obtained by applying \( at\) on c.

Precondition

at is an orthogonal transformation.

squared_radius()

template<typename Kernel >

const Kernel::FT & CGAL::Circle_2< Kernel >::squared_radius

(

)

const

returns the squared radius of c.

Exactness

This construction is trivial and therefore always exact in Exact_predicates_inexact_constructions_kernel.