class Utils

	shared

		def join(sep as String, parts as System.Collections.IEnumerable) as String
			test
				assert Utils.join('.', ['a', 'b'])=='a.b'
			body
				sb as StringBuilder = StringBuilder()
				s = ''
				for part in parts  # compiler used to choke on inferring type of part from parts
					sb.append(s)
					sb.append(part.toString)
					s = sep
				return sb.toString

		def main
			pass