# Display up to `count` most used elements and `count` least used elements
	# Use `element_to_s` to display the element
	fun print_elements(count: Int)
	do
		print " list:"
		var list = self.sort
		var min = count
		if list.length <= count*2 then min = list.length
		for i in [0..min[ do
			var t = list[list.length-i-1]
			print "  {element_to_s(t)}: {self[t]} ({div(self[t]*100,self.sum)}%)"
		end
		if list.length <= count*2 then return
		print "  ..."
		for i in [0..min[ do
			var t = list[min-i-1]
			print "  {element_to_s(t)}: {self[t]} ({div(self[t]*100,self.sum)}%)"
		end
	end