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igraph_datatype.h
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igraph_datatype.h
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/* -*- mode: C -*- */
/*
IGraph library.
Copyright (C) 2009-2012 Gabor Csardi <csardi.gabor@gmail.com>
334 Harvard street, Cambridge, MA 02139 USA
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
#ifndef IGRAPH_DATATYPE_H
#define IGRAPH_DATATYPE_H
#undef __BEGIN_DECLS
#undef __END_DECLS
#ifdef __cplusplus
# define __BEGIN_DECLS extern "C" {
# define __END_DECLS }
#else
# define __BEGIN_DECLS /* empty */
# define __END_DECLS /* empty */
#endif
#include "igraph_types.h"
#include "igraph_vector.h"
__BEGIN_DECLS
/**
* \ingroup internal
* \struct igraph_t
* \brief The internal data structure for storing graphs.
*
* It is simple and efficient. It has the following members:
* - <b>n</b> The number of vertices, reduntant.
* - <b>directed</b> Whether the graph is directed.
* - <b>from</b> The first column of the edge list.
* - <b>to</b> The second column of the edge list.
* - <b>oi</b> The index of the edge list by the first column. Thus
* the first edge according to this order goes from
* \c from[oi[0]] to \c to[oi[0]]. The length of
* this vector is the same as the number of edges in the graph.
* - <b>ii</b> The index of the edge list by the second column.
* The length of this vector is the same as the number of edges.
* - <b>os</b> Contains pointers to the edgelist (\c from
* and \c to for every vertex. The first edge \em from
* vertex \c v is edge no. \c from[oi[os[v]]] if
* \c os[v]<os[v+1]. If \c os[v]==os[v+1] then
* there are no edges \em from node \c v. Its length is
* the number of vertices plus one, the last element is always the
* same as the number of edges and is contained only to ease the
* queries.
* - <b>is</b> This is basically the same as <b>os</b>, but this time
* for the incoming edges.
*
* For undirected graph, the same edge list is stored, ie. an
* undirected edge is stored only once, and for checking whether there
* is an undirected edge from \c v1 to \c v2 one
* should search for both \c from=v1, \c to=v2 and
* \c from=v2, \c to=v1.
*
* The storage requirements for a graph with \c |V| vertices
* and \c |E| edges is \c O(|E|+|V|).
*/
typedef struct igraph_s {
igraph_integer_t n;
igraph_bool_t directed;
igraph_vector_t from;
igraph_vector_t to;
igraph_vector_t oi;
igraph_vector_t ii;
igraph_vector_t os;
igraph_vector_t is;
void *attr;
} igraph_t;
__END_DECLS
#endif