| 閏年か？ |

閏年か？ := [:int |
	((0 to: Float infinity by: 4) includes: int)
		and: [((0 to: Float infinity by: 100) includes: int) not
			or: [(0 to: Float infinity by: 400) includes: int]]].

閏年か？ value: 1900.   "=> false "
閏年か？ value: 2000.   "=> true "
閏年か？ value: 2008.   "=> true "
閏年か？ value: 2100.   "=> false "