Segment_2<Kernel>

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CGAL::Segment_2<Kernel>

Definition

An object

s of the data type Segment_2<Kernel> is a directed straight line segment in the two-dimensional Euclidean plane

², i.e. a straight line segment

[p,q] connecting two points

p,q in

². The segment is topologically closed, i.e. the end points belong to it. Point

p is called the source and

q is called the target of

s. The length of

s is the Euclidean distance between

p and

q. Note that there is only a function to compute the square of the length, because otherwise we had to perform a square root operation which is not defined for all number types, which is expensive, and may not be exact.

Creation

Segment_2<Kernel> s ( Point_2<Kernel> p, Point_2<Kernel> q);
	introduces a segment s with source p and target q. The segment is directed from the source towards the target.

Operations

bool	s.operator== ( q)	Test for equality: Two segments are equal, iff their sources and targets are equal.

bool	s.operator!= ( q)	Test for inequality.

Point_2<Kernel>	s.source ()	returns the source of s.

Point_2<Kernel>	s.target ()	returns the target of s.
Point_2<Kernel>	s.min ()	returns the point of s with lexicographically smallest coordinate.

Point_2<Kernel>	s.max ()	returns the point of s with lexicographically largest coordinate.

Point_2<Kernel>	s.vertex ( int i)	returns source or target of s: vertex(0) returns the source of s, vertex(1) returns the target of s. The parameter i is taken modulo 2, which gives easy access to the other vertex.

Point_2<Kernel>	s.point ( int i)	returns vertex(i).

Point_2<Kernel>	s.operator[] ( int i)	returns vertex(i).

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

Direction_2<Kernel>	s.direction ()	returns the direction from source to target of s.

Vector_2<Kernel>	s.to_vector ()	returns the vector s.target() - s.source().

Segment_2<Kernel>	s.opposite ()	returns a segment with source and target point interchanged.

Line_2<Kernel>	s.supporting_line ()	returns the line l passing through s. Line l has the same orientation as segment s.

Predicates

bool

s.is_degenerate ()

segment s is degenerate, if source and target are equal.

bool

s.is_horizontal ()

bool

s.is_vertical ()

bool

s.has_on ( Point_2<Kernel> p)

A point is on s, iff it is equal to the source or target of s, or if it is in the interior of s.

bool

s.collinear_has_on ( Point_2<Kernel> p)

checks if point

p is on segment s. This function is faster than function has_on().

Precondition:

p is on the supporting line of s.

Miscellaneous

Bbox_2	s.bbox ()	returns a bounding box containing s.

Segment_2<Kernel>	s.transform ( Aff_transformation_2<Kernel> t)
		returns the segment obtained by applying t on the source and the target of s.

CGAL::Segment_2<Kernel>

Definition

Creation

Operations

Predicates

Miscellaneous

See Also