[swift-evolution] Feature proposal: Range operator with step

Howard Lovatt howard.lovatt at gmail.com
Tue Mar 29 22:58:03 CDT 2016

Good idea to add `seconds`/`days`/`solarMonths`/`lunarMonths`/etc. views
that are Strideable

  -- Howard.

On 30 March 2016 at 13:57, Joe Groff via swift-evolution <
swift-evolution at swift.org> wrote:

> > On Mar 28, 2016, at 5:33 PM, Brent Royal-Gordon <brent at 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).
> -Joe
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