Data commit

Task/Doomsday-rule/Wren/doomsday-rule.wren

@@ -0,0 +1,38 @@
+import "/date" for Date
+
+var days = ["Sunday", "Monday", "Tuesday", "Wednesday","Thursday", "Friday", "Saturday"]
+
+var anchorDay = Fn.new { |y| (2 + 5 * (y%4) + 4 *(y%100) + 6 * (y%400)) % 7 }
+
+var isLeapYear = Fn.new { |y| y%4 == 0 && (y%100 != 0 || y%400 == 0) }
+
+var firstDaysCommon = [3, 7, 7, 4, 2, 6, 4, 1, 5, 3, 7, 5]
+var firstDaysLeap   = [4, 1, 7, 4, 2, 6, 4, 1, 5, 3, 7, 5]
+
+var dates = [
+    "1800-01-06",
+    "1875-03-29",
+    "1915-12-07",
+    "1970-12-23",
+    "2043-05-14",
+    "2077-02-12",
+    "2101-04-02"
+]
+
+System.print("Days of week given by Doomsday rule:")
+for (date in dates) {
+    var y = Num.fromString(date[0..3])
+    var m = Num.fromString(date[5..6]) - 1
+    var d = Num.fromString(date[8..9])
+    var a = anchorDay.call(y)
+    var w = d - (isLeapYear.call(y) ? firstDaysLeap[m] : firstDaysCommon[m])
+    if (w < 0) w = 7 + w
+    var dow = (a + w) % 7
+    System.print("%(date) -> %(days[dow])")
+}
+
+System.print("\nDays of week given by Date module:")
+for (date in dates) {
+    var d = Date.parse(date, Date.isoDate)
+    System.print("%(date) -> %(d.weekDay)")
+}