on Tue Mar 29 2016, Joe Groff <jgroff-AT-apple.com> wrote: >> On Mar 28, 2016, at 5:33 PM, Brent Royal-Gordon <[email protected]> >> wrote: >> >>>> Floating-point seconds (as NSTimeIntervals) are the natural >>> Strideable.Stride, but it's not particularly clear to me that you >>> want 1 second to be a default stride. It's the default you would > >>> guess, but it's not actually a particularly useful default. >>> >>> Any fixed-time-period stride with dates is fraught with peril. Not >>> every day is 24 hours, not every minute is 60 seconds, etc. Working >>> with dates requires enough special domain knowledge that I think >>> it'd be harmful to try to genericize numeric concepts over it. >> >> While this is true, "ten seconds from now" is always ten seconds >> from now, and "seconds between date1 and date2" is always the same >> number of seconds. There is a basic level of time measurement and >> manipulation which is completely independent of time zones and >> calendars; that's what NSDate and NSTimeInterval represent. They are >> needed fairly often, and they are perfectly compatible with >> Strideable's semantics. > > Perhaps, but if you make Date strideable by seconds and automatically > receive a bunch of utility methods based on that, then it becomes > really tempting to abuse absolute time periods, or to accidentally > misuse generic Strideable utilities instead of calendar-aware ones. We > don't make String a sequence for similar reasons (though perhaps, by > analogy to String, there could be > `seconds`/`days`/`solarMonths`/`lunarMonths`/etc. views that are > Strideable).
Except that collections aren't Strideable. A strideable type is a value that has an implied unit of measure so that you can offset it without reference to any collection. -- Dave _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution
