Vector_2<Kernel>

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CGAL::Vector_2<Kernel>

Definition

An object of the class Vector_2<Kernel> is a vector in the two-dimensional vector space ². Geometrically spoken, a vector is the difference of two points p₂, p₁ and denotes the direction and the distance from p₁ to p₂.

CGAL defines a symbolic constant NULL_VECTOR. We will explicitly state where you can pass this constant as an argument instead of a vector initialized with zeros.

Creation

Vector_2<Kernel> v ( Point_2<Kernel> a, Point_2<Kernel> b);

introduces the vector

b-a.

Vector_2<Kernel> v ( Segment_2<Kernel> s);

introduces the vector

s.target()-s.source().

Vector_2<Kernel> v ( Ray_2<Kernel> r);

introduces the vector having the same direction as

Vector_2<Kernel> v ( Line_2<Kernel> l);

introduces the vector having the same direction as

Vector_2<Kernel> v ( Null_vector NULL_VECTOR);

introduces a null vector v.

Vector_2<Kernel> v ( int x, int y);

introduces a vector v initialized to

(x,y).

Vector_2<Kernel> v ( double x, double y);

introduces a vector v initialized to

(x,y).

Vector_2<Kernel> v ( Kernel::RT hx, Kernel::RT hy, Kernel::RT hw = RT(1));

introduces a vector v initialized to

(hx/hw,hy/hw).

Precondition:

hw not equal to 0

Vector_2<Kernel> v ( Kernel::FT x, Kernel::FT y);

introduces a vector v initialized to

(x,y).

Operations

bool	v.operator== ( w)	Test for equality: two vectors are equal, iff their x and y coordinates are equal. You can compare a vector with the NULL_VECTOR.

bool	v.operator!= ( w)	Test for inequality. You can compare a vector with the NULL_VECTOR.

There are two sets of coordinate access functions, namely to the homogeneous and to the Cartesian coordinates. They can be used independently from the chosen kernel model.

Kernel::RT	v.hx ()	returns the homogeneous x coordinate.
Kernel::RT	v.hy ()	returns the homogeneous y coordinate.
Kernel::RT	v.hw ()	returns the homogenizing coordinate.

Note that you do not loose information with the homogeneous representation, because the FieldNumberType is a quotient.

Kernel::FT	v.x ()	returns the x-coordinate of v, that is hx/hw.
Kernel::FT	v.y ()	returns the y-coordinate of v, that is hy/hw.

The following operations are for convenience and for compatibility with higher dimensional vectors. Again they come in a Cartesian and homogeneous flavor.

Kernel::RT

v.homogeneous ( int i)

returns the i'th homogeneous coordinate of v, starting with 0.

Precondition:

0 i 2.

Kernel::FT

v.cartesian ( int i)

returns the i'th Cartesian coordinate of v, starting at 0.

Precondition:

0 i 1.

Kernel::FT

v.operator[] ( int i)

returns cartesian(i).

Precondition:

0 i 1.

int

v.dimension ()

returns the dimension (the constant 2).

Direction_2<Kernel>

v.direction ()

returns the direction which passes through v.

Vector_2<Kernel>

v.transform ( Aff_transformation_2<Kernel> t)

returns the vector obtained by applying

t on v.

Vector_2<Kernel>

v.perpendicular ( Orientation o)

returns the vector perpendicular to v in clockwise or counterclockwise orientation.

Operators

The following operations can be applied to vectors:

Vector_2<Kernel>	v.operator+ ( w)	Addition.

Vector_2<Kernel>	v.operator- ( w)	Subtraction.

Vector_2<Kernel>	v.operator- ()	returns the opposite vector.

Kernel::FT	v.operator ( w)*	returns the scalar product (= inner product) of the two vectors.

Vector_2<Kernel>	operator ( v, Kernel::RT s)*	Multiplication with a scalar from the right.

Vector_2<Kernel>	operator ( v, Kernel::FT s)*	Multiplication with a scalar from the right.

Vector_2<Kernel>	operator ( Kernel::RT s, v)*	Multiplication with a scalar from the left.

Vector_2<Kernel>	operator ( Kernel::FT s, v)*	Multiplication with a scalar from the left.

Vector_2<Kernel>	v.operator/ ( Kernel::RT s)	Division by a scalar.

Kernel::FT	v.squared_length ()	returns the squared length of v.

CGAL::Vector_2<Kernel>

Definition

Creation

Operations

Operators

See Also