> On Mar 30, 2016, at 11:42 AM, Dave Abrahams <dabrah...@apple.com> wrote: > > > on Wed Mar 30 2016, Joe Groff <jgroff-AT-apple.com> wrote: > >>> On Mar 30, 2016, at 8:50 AM, Dave Abrahams <dabrah...@apple.com> wrote: >>> >>> >>> on Tue Mar 29 2016, Joe Groff <jgroff-AT-apple.com> wrote: >>> >> >>>>> On Mar 28, 2016, at 5:33 PM, Brent Royal-Gordon <br...@architechies.com> >>>>> 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. >> >> Who said anything about collections? > > That's what those views are.
Sure, but I was making an analogy. String isn't a Collection by itself because operating on pieces of a string usually requires a lot of domain-specific knowledge, yet we provide Collection views that present it as a collection of user-chosen units. Date (IMO) shouldn't be Strideable for similar reasons, since correctly manipulating dates requires a lot of domain-specific knowledge, yet we could provide Strideable views of a Date that advances by user-selected intervals. I wasn't claiming Date was a collection. -Joe _______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
