vertexSet-class: Class "vertexSet"
Description
Class for vertex setsObjects from the Class
Objects can be created by calls of the form new("vertexSet", ...)
which admit short-hands of the form v(...).Slots
    .Data:- Object of class 
"vector"
	storing unique character identifiers that are sintactically valid names  
 Extends
Class "character", from data part.
Class "vector", by class "character".Methods
    - initialize
 signature(.Object = "vertexSet"):
	  constructs a vertex set from a vector of unique sintactically valid names  - show
 signature(object = "vertexSet"):
	  displays a vertex set as comma separated characters in graph brackets  - areTheSame
 signature(x = "vertexSet", y = "vertexSet"):
	  x and y are the same vertex set if they are the same set of character identifiers  - [
 signature(x = "vertexSet"): extracts a vertex set  - coerce
 signature(from = "vector", to = "vertexSet"): constructs a vertex set from vector input  - names
 signature(x = "vertexSet"): gets the character vertex identifiers  - +
 signature(e1 = "vertexSet", e2 = "vertexSet"): performs the union of two vertex sets  - *
 signature(e1 = "vertexSet", e2 = "vertexSet"): performs the intersection of two vertex sets  - -
 signature(e1 = "vertexSet", e2 = "vertexSet"): performs the asymmetric difference of two vertex sets  
 Warning 
The constructor will try to handle any vector input
by silently transforming it into a vector of unique sintactically valid names
obtained via make.names from the unique input elements.See Also
The short-hand v.