# vertexSet -- Returns the vertices of a graph or digraph

## Synopsis

• Usage:
V = vertexSet D
V = vertexSet G
• Inputs:
• D, an instance of the type Digraph
• G, an instance of the type Digraph
• Outputs:
• V, a list, The vertices of digraph D

## Description

The vertices of a graph are just singletons that can be indexed by numbers, letters, or even in some cases something as exotic as a monomial. These form the base of a graph; the edges are 2 member subsets of the vertex set of a graph.

 i1 : D = digraph({{1,2},{2,1},{3,1}},EntryMode=>"edges"); i2 : vertexSet D; i3 : G = completeGraph 4; i4 : vertexSet G o4 = {0, 1, 2, 3} o4 : List i5 : A = adjacencyMatrix G; 4 4 o5 : Matrix ZZ <--- ZZ i6 : graph({a,b,c,d}, A) o6 = Graph{a => {b, c, d}} b => {a, c, d} c => {a, b, d} d => {a, b, c} o6 : Graph