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Note that the
two functions UnderlyingGraph and UnderlyingDigraph
may also be used when one needs to get a copy of a graph G
without G's support and vertex/edge decorations.
Given a graph G, produce a digraph D whose vertex-set is the same as
that of G and whose edge-set consists of the edges of G, each given
a direction. The edges of D are always directed from the
lower numbered vertex to the higher numbered vertex. Thus, if G
contains the edge { u, v }, then D will have the edge
[u, v] if u < v, otherwise the edge [u, v].
The support and vertex/edge decorations of G are not retained.
The underlying graph G of the graph D;
G has the same vertex-set as D.
If D is undirected, then G is a copy of D
without D's support and vertex/edge decorations.
If D is directed, then two vertices u and v are adjacent in G
if and only if, in D, there is either an edge directed from u to
v or from v to u.
The support and vertex/edge decorations of G are not retained.
The underlying digraph D of the graph G;
D has the same vertex-set as G.
If G is directed, then D is a copy of G
without D's support and vertex/edge decorations.
If G is undirected, then if vertices u and v are adjacent in G
then, in D, there will be both an edge directed from u to v and
an edge directed from v to u.
The support and vertex/edge decorations of G are not retained.
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