Set = new map
Set["set"] = {}

Set.init = function(items)
	set = new Set
	set.set = {}
	for item in items
		set.add(item)
	end for
	return set
end function

Set.contains = function(item)
	return self.set.hasIndex(item)
end function

Set.items = function
	return self.set.indexes
end function

Set.add = function(item)
	self.set[item] = true
end function

Set.union = function(other)
	result = Set.init
	result.set = self.set + other.set
	return result
end function

Set.difference = function(other)
	result = Set.init
	for item in self.items
		if not other.contains(item) then result.add(item)
	end for
	return result
end function

Set.symmetricDifference = function(other)
	diff1 = self.difference(other)
	diff2 = other.difference(self)
	return diff1.union(diff2)
end function

a = ["John", "Serena", "Bob", "Mary", "Serena"]
b = ["Jim", "Mary", "John", "Jim", "Bob"]

A1 = Set.init(a)
B1 = Set.init(b)

print "A XOR B " + A1.symmetricDifference(B1).items
print "A - B " + A1.difference(B1).items
print "B - A " + B1.difference(A1).items