Description: Define the class of all
undirected simple graphs without loops. An
undirected simple graph without loops is a special undirected simple
graph    where is an injective (one-to-one) function
into subsets of of cardinality two, representing the two vertices
incident to the edge. Such graphs are usually simply called
"undirected
graphs", so if only the term "undirected graph" is used,
an undirected
simple graph without loops is meant. Therefore, an undirected graph has
no loops (edges a vertex to itself). (Contributed by Alexander van der
Vekens, 10-Aug-2017.) |