lib(ordset)

	In this module, sets are represented by ordered lists with no
	duplicates.  Thus the set {c,r,a,f,t} would be [a,c,f,r,t].  The
	ordering is defined by the @
	The benefit of the ordered representation is that the elementary
	set operations can be done in time proportional to the Sum of
	the argument sizes rather than their Product.  Some of the
	unordered set routines, such as member/2, length/2, select/3
	can be used unchanged.
	
	The implementation allows nonground set elements. The only problem
	with this is that a set can lose its set property as a result of
	variable bindings: unifications can create duplicates or change
	the element's position in the term order. The set can be repaired
	by applying list_to_ord_set/2 again, i.e. re-sorting it.
	
	Note that the predicates of this library do no error checking.
	When called with the wrong argument types or modes, the result is
	undefined.
	
    

