Data commit

Task/Five-weekends/Ceylon/five-weekends-1.ceylon

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+module rosetta.fiveweekends "1.0.0" {
+    import ceylon.time "1.2.2";
+}

Task/Five-weekends/Ceylon/five-weekends-2.ceylon

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+import ceylon.time {
+    date,
+    Date
+}
+import ceylon.time.base {
+    january,
+    december,
+    friday,
+    Month
+}
+
+shared void run() {
+    [Date[],Integer[]] result = fiveWeekendsRecursive();
+
+    value fiveWeekendFirstOfMonths = result[0];
+    Integer[] yearsWithNoFiveWeekendMonths = result[1];
+
+    print("# five weekend months = ``fiveWeekendFirstOfMonths.size``");
+    print("# years without five weekend months = ``yearsWithNoFiveWeekendMonths.size``");
+    yearsWithNoFiveWeekendMonths.each(print);
+}
+
+[Date[], Integer[]] fiveWeekendsRecursive()
+    => fiveWeekendsRecursiveInner{ year = 1900;
+                                   month = january;
+                                   fiveWeekendFirstOfMonths = [];
+                                   yearsWithNoFiveWeekendMonths = []; };
+
+[Date[], Integer[]] fiveWeekendsRecursiveInner(Integer year,
+                                               Month month,
+                                               Date[] fiveWeekendFirstOfMonths,
+                                               Integer[] yearsWithNoFiveWeekendMonths) {
+    if (year > 2100) {
+        return [fiveWeekendFirstOfMonths,yearsWithNoFiveWeekendMonths];
+    }
+
+    Date firstOfMonth = date{ year = year; month = month; day = 1; };
+
+    Boolean isFiveWeekendMonth =
+         (month.numberOfDays() == 31 && friday == firstOfMonth.dayOfWeek);
+
+    Boolean hasNoFiveWeekends =
+        month == december &&
+        ! isFiveWeekendMonth &&
+        fiveWeekendFirstOfMonths.filter((date) => date.year == year).size == 0;
+
+    return fiveWeekendsRecursiveInner(if (month == december) then year+1 else year,
+                                      if (month == december) then january else month.plusMonths(1),
+                                      if (isFiveWeekendMonth)
+                                        then fiveWeekendFirstOfMonths.withTrailing(firstOfMonth)
+                                        else fiveWeekendFirstOfMonths,
+                                      if (hasNoFiveWeekends)
+                                        then yearsWithNoFiveWeekendMonths.withTrailing(year)
+                                        else yearsWithNoFiveWeekendMonths);
+}