What if we were to support day-of-week?

[michi-oshima]

(Is this the only way to post a comment?)

Hi Tim,

Thanks for the code. Just three short and beautiful functions! (I still don't fully understand how the lazy seq thing works.)

I notice you also correctly take care of the number of days in a month.

I'm going to change the problem on you a bit, hopefully making it harder. (Sorry!)

If we were to support day-of-week for specifying days, how would you go about it? For example, something like this:

• { :day-of-week [:tuesday :thursday] :hour 18 :minute 30 } (Every Tuesday and Thursday at 6:30pm)

[ohpauleez]

A totally unrelated comment - When I thought about solving the actual problem, I also first thought about using clj-time/Joda Time. I decided against it to illustrate how localized "state" happens in functions (even if that meant I didn't solve the actual problem). In the real world, I would definitely take a route closer to what Tim did than what I did.

[tmciver]

Concerning the lazy seq question: a lot of clojure functions produce lazy seqs, such as drop-while and for used in the all-events-from function. This function produces an infinite sequence and therefore must be produced lazily. You shouldn't try to display an infinite sequence at the REPL: use take:

(require '[clj-time.core :as t])
(def events (all-events-from (t/now) {:day [1 14 30] :min [0 15 30 45]}))
(take 5 events)

This will display the first 5 events.

Concerning the question about day-of-week: I'm sure that could be supported. A question to you is: why not go all the way and implement this as using a 'real' cron schedule? That would be a schedule with the following keys:

[:minute :hour :day-of-month :month :day-of-week]