sig MakeString as String


class X

	def main
		s = .stringForInt(5, do='5')
		assert s == '5'
		s = .stringForInt(5, do='5')
		assert s == '5'
		s = .stringForInt(3, do=_makeString(3))  # used to bug out here

	var _cache = Dictionary<of int, String>()
	
	def stringForInt(i as int, makeString as MakeString) as String
		if _cache.containsKey(i)
			return _cache[i]
		else
			s = makeString()
			_cache[i] = s
			return s

	def _makeString(i as int) as String
		return i.toString