geos::planargraph::DirectedEdge Class Reference

Represents a directed edge in a PlanarGraph. More...

#include <DirectedEdge.h>

Inheritance diagram for geos::planargraph::DirectedEdge:

List of all members.

Public Types
typedef std::list< DirectedEdge * >	NonConstList
typedef std::list< const DirectedEdge * >	ConstList
typedef std::vector< DirectedEdge * >	NonConstVect
typedef std::vector< const DirectedEdge * >	ConstVect
typedef std::vector< DirectedEdge * >	Vect
Public Member Functions
	DirectedEdge (Node *newFrom, Node *newTo, const geom::Coordinate &directionPt, bool newEdgeDirection)
	Constructs a DirectedEdge connecting the from node to the to node.
Edge *	getEdge () const
	Returns this DirectedEdge's parent Edge, or null if it has none.
void	setEdge (Edge *newParentEdge)
	Associates this DirectedEdge with an Edge (possibly null, indicating no associated Edge).
int	getQuadrant () const
	Returns 0, 1, 2, or 3, indicating the quadrant in which this DirectedEdge's orientation lies.
const geom::Coordinate &	getDirectionPt () const
	Returns a point to which an imaginary line is drawn from the from-node to specify this DirectedEdge's orientation.
bool	getEdgeDirection () const
	Returns whether the direction of the parent Edge (if any) is the same as that of this Directed Edge.
Node *	getFromNode () const
	Returns the node from which this DirectedEdge leaves.
Node *	getToNode () const
	Returns the node to which this DirectedEdge goes.
geom::Coordinate &	getCoordinate () const
	Returns the coordinate of the from-node.
double	getAngle () const
	Returns the angle that the start of this DirectedEdge makes with the positive x-axis, in radians.
DirectedEdge *	getSym () const
	Returns the symmetric DirectedEdge -- the other DirectedEdge associated with this DirectedEdge's parent Edge.
void	setSym (DirectedEdge *newSym)
	Sets this DirectedEdge's symmetric DirectedEdge, which runs in the opposite direction.
int	compareTo (const DirectedEdge *obj) const
	Returns 1 if this DirectedEdge has a greater angle with the positive x-axis than b", 0 if the DirectedEdges are collinear, and -1 otherwise.
int	compareDirection (const DirectedEdge *e) const
	Returns 1 if this DirectedEdge has a greater angle with the positive x-axis than b", 0 if the DirectedEdges are collinear, and -1 otherwise.
std::string	print () const
	Prints a detailed string representation of this DirectedEdge to the given PrintStream.
Static Public Member Functions
static std::vector< Edge * > *	toEdges (std::vector< DirectedEdge * > &dirEdges)
	Returns a List containing the parent Edge (possibly null) for each of the given DirectedEdges.
static void	toEdges (std::vector< DirectedEdge * > &dirEdges, std::vector< Edge * > &parentEdges)
	Add parent Edge (possibly null) of each of the given DirectedEdges to the given parentEdges vector.
Protected Attributes
Edge *	parentEdge
Node *	from
Node *	to
geom::Coordinate	p0
geom::Coordinate	p1
DirectedEdge *	sym
bool	edgeDirection
int	quadrant
double	angle

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Detailed Description

Represents a directed edge in a PlanarGraph.

A DirectedEdge may or may not have a reference to a parent Edge (some applications of planar graphs may not require explicit Edge objects to be created). Usually a client using a PlanarGraph will subclass DirectedEdge to add its own application-specific data and methods.

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Constructor & Destructor Documentation

geos::planargraph::DirectedEdge::DirectedEdge (  Node *  newFrom, Node *  newTo, const geom::Coordinate &  directionPt, bool  newEdgeDirection )

Constructs a DirectedEdge connecting the from node to the to node. Parameters: directionPt  specifies this DirectedEdge's direction (given by an imaginary line from the from node to directionPt) edgeDirection  whether this DirectedEdge's direction is the same as or opposite to that of the parent Edge (if any)

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Member Function Documentation

int geos::planargraph::DirectedEdge::compareDirection (  const DirectedEdge *  e  )  const

Returns 1 if this DirectedEdge has a greater angle with the positive x-axis than b", 0 if the DirectedEdges are collinear, and -1 otherwise. Using the obvious algorithm of simply computing the angle is not robust, since the angle calculation is susceptible to roundoff. A robust algorithm is: first compare the quadrants. If the quadrants are different, it it trivial to determine which std::vector is "greater". if the vectors lie in the same quadrant, the robust RobustCGAlgorithms::computeOrientation(Coordinate, Coordinate, Coordinate) function can be used to decide the relative orientation of the vectors.

int geos::planargraph::DirectedEdge::compareTo (  const DirectedEdge *  obj  )  const

Returns 1 if this DirectedEdge has a greater angle with the positive x-axis than b", 0 if the DirectedEdges are collinear, and -1 otherwise. Using the obvious algorithm of simply computing the angle is not robust, since the angle calculation is susceptible to roundoff. A robust algorithm is: first compare the quadrants. If the quadrants are different, it it trivial to determine which std::vector is "greater". if the vectors lie in the same quadrant, the robust RobustCGAlgorithms::computeOrientation(Coordinate, Coordinate, Coordinate) function can be used to decide the relative orientation of the vectors.

static void geos::planargraph::DirectedEdge::toEdges (  std::vector< DirectedEdge * > &  dirEdges, std::vector< Edge * > &  parentEdges )  [static]

Add parent Edge (possibly null) of each of the given DirectedEdges to the given parentEdges vector. NOTE: parents are pushed to the parentEdges vector, make sure it is empty if index-based corrispondence is important.

static std::vector<Edge*>* geos::planargraph::DirectedEdge::toEdges (  std::vector< DirectedEdge * > &  dirEdges  )  [static]

Returns a List containing the parent Edge (possibly null) for each of the given DirectedEdges. NOTE: ownership of the returned vector is left to the caller, see the equivalent function taking a vector reference to avoid this.

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The documentation for this class was generated from the following file:

• planargraph/DirectedEdge.h

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