Face Circulators ( FaceCirc )

Definition

a variable fc of class FaceCirc is a face circulator that circulates through the set of edges of a face as long as the graph is embedded combinatorically correct, i.e. the graph has to be bidirected and a map (see graph).

#include < LEDA/graph/graph_iterator.h >

Creation

FaceCirc	fc	introduces a variable fc of this class associated with no graph.
FaceCirc	fc(const leda::graph& G)	introduces a variable fc of this class associated with G. The edge is initialized to nil.
FaceCirc	fc(const leda::graph& G, leda::edge e)
		introduces a variable fc of this class marked with e and associated with G. Precondition: e is an edge of G.

Operations

void	fc.init(const leda::graph& G)
		associates fc with G.
void	fc.init(const leda::graph& G, const leda::edge& e)
		associates fc with G and marks it with e. Precondition: e is an edge of G.
void	fc.update(leda::edge e)	fc marks e afterwards.
void	fc.make_invalid()	makes fc invalid, i.e. fc.valid() will be false afterwards and fc marks no edge.
FaceCirc&	fc = const FaceCirc& fc2	assigns fc2 to fc. This method returns a reference to fc.
bool	fc == const FaceCirc& fc2	returns true if and only if fc and fc2 are equal, i.e. if the marked edges are equal.
bool	fc.has_edge()	returns true if and only if fc marks an edge.
bool	fc.eol()	returns !fc.valid().
bool	fc.valid()	returns true if and only if the circulator is marked with an edge.
leda::edge	fc.get_edge()	returns the marked edge or nil if fc.valid() returns false.
const leda::graph&	fc.get_graph()	returns the associated graph.
FaceCirc&	++fc	redirects the circulator to the cyclic adjacency predecessor of reversal(e), where e is the marked edge. This method returns a reference to fc. Precondition: fc.valid() returns true.
FaceCirc&	-fc	redirects the circulator to the cyclic adjacency successor of e, where e is the marked edge. This method returns a reference to fc. Precondition: fc.valid() returns true.

Implementation

Creation of a circulator and all methods take constant time.