<https://kotlinlang.slack.com/archives/general/p14...

# announcements

[ilya.gorbunov]

https://kotlinlang.slack.com/archives/general/p1447723111000696
We couldn't find cases where having common Progression<N> interface implemented by concrete progressions would be beneficial.
You can create a DateProgression without implementing Progression interface — just make it implement Iterable<Date>