Construct date sequence in Scala

Question

I want to have a continuous date sequence like ['2014-01-01','2014-01-02', ...]

Then I define a stream to do that.

def daySeq(start: Date): Stream[Date] = Stream.cons(start,  daySeq(plusDays(start, 1)))

I get the sequence within range [start, end) by calling

daySeq(from).takeWhile(_.getTime < to.getTime)

Any better/simple solution to do this ?

Dave Swartz · Accepted Answer · 2014-03-23 03:37:22Z

I suggest using Joda-Time's LocalDate instead of Java's Date to represent dates without a time zone.

Assuming you only need to traverse the days once, use an Iterator instead of a Stream.

def dayIterator(start: LocalDate, end: LocalDate) = Iterator.iterate(start)(_ plusDays 1) takeWhile (_ isBefore end)

Example usage:

dayIterator(new LocalDate("2013-10-01"), new LocalDate("2014-01-30")).foreach(println)

If you do need a lazily-evaluated list, then Stream is appropriate. I suggest using iterate instead of cons in that case.

def dayStream(start: LocalDate, end: LocalDate) = Stream.iterate(start)(_ plusDays 1) takeWhile (_ isBefore end)

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