# Create and fill up a counter with the elements of `self.
	#
	# ~~~
	# var cpt = "abaa".chars.to_counter
	# assert cpt['a'] == 3
	# assert cpt['b'] == 1
	# assert cpt.length == 2
	# assert cpt.sum == 4
	# ~~~
	fun to_counter: Counter[E]
	do
		var res = new Counter[E]
		res.inc_all(self)
		return res
	end