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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 ∈ ℝ2. 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) const Test for equality: Two segments are equal, iff their sources and targets are equal.

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

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

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

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

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

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

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

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

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

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

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

Predicates

bool s.is_degenerate () const segment s is degenerate, if source and target are equal.

bool s.is_horizontal () const
bool s.is_vertical () const

bool s.has_on ( Point_2<Kernel> p) const
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) const
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 () const returns a bounding box containing s.

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

See Also

Kernel::Segment_2

Next: Triangle_2<Kernel>
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CGAL Open Source Project. Release 3.9. 26 September 2011.