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

[Xiaodi Wu]

Right. I would argue that `(a+s...b).striding(by: s).reversed` is a great
deal less readable than `stride(from: b, to: a, by: -s)`. And since the
latter is the status quo, I would say that it's a point against restricting
strides to the proposed syntax.

On Tue, Apr 5, 2016 at 3:57 PM Dave Abrahams via swift-evolution <
swift-evolution at swift.org> wrote:

>
> on Tue Apr 05 2016, Xiaodi Wu <swift-evolution at swift.org> wrote:
>
> > Certainly, for integer literals and strides of -1.
> >
> > I meant more generally that removal of stride(...) will eliminate the
> > possibility of striding to but not through arbitrary half-open intervals
> (a, b],
> > where a < b, by a negative increment, because there is no such thing as
> `a>..b`
> > to express such an interval as a Swift range.
> > Of course, all such cases can be handled by adjusting the endpoint and
> using a
> > closed range instead
> >
>
> Indeed, if b - a is a multiple of s,
>
>    (a+s...b).striding(by: s).reversed
>
> works.
>
> The question is whether this case is important enough to create a
> special family of functions for, and then deal with the naming issues
> raised by
>
> https://github.com/apple/swift-evolution/blob/master/proposals/0051-stride-semantics.md
> ?
>
> > On Tue, Apr 5, 2016 at 2:54 PM Dave Abrahams
> > <dabrahams at apple.com> wrote:
> >
> >     on Tue Apr 05 2016, Xiaodi Wu <xiaodi.wu-AT-gmail.com> wrote:
> >
> >     > On Mon, Apr 4, 2016 at 1:22 PM, Dave Abrahams
> >     <dabrahams at apple.com> wrote:
> >     >>
> >     >> on Sat Apr 02 2016, Xiaodi Wu <xiaodi.wu-AT-gmail.com> wrote:
> >     >>
> >     >>> [snip]
> >     >>>
> >     >>> Not included:
> >     >>> 1. I know Ranges are in flux, so I've held off on extending
> Range with
> >     >>> a striding(by:) method in this proof-of-concept.
> >     >>
> >     >> They're not in flux, except for not having been reviewed yet;
> they are
> >     >> settled in the swift-3-indexing-model branch.
> >     >
> >     > Did not know that. Will have to study what's there in more detail.
> >     >
> >     >>> 2. No attempt at the suggested stride(from:to:steps:) quite yet.
> >     >>
> >     >> #1 and #2 are mutually exclusive; we prefer #1 as it removes
> questions
> >     >> about the meaning of "to" or "through."
> >     >
> >     > I wasn't aware that was the thinking. Limiting strides to
> >     > `striding(by:)` removes the ability to express `stride(from: 0, to:
> >     > -10, by: -1)`
> >
> >     IMO this:
> >
> >     (-9...0).reverse()
> >
> >     is better than
> >
> >     stride(from: 0, to: -10, by: -1)
> >
> >     What do you think?
> >
> >     --
> >     Dave
> >
> > _______________________________________________
> > swift-evolution mailing list
> > swift-evolution at swift.org
> > https://lists.swift.org/mailman/listinfo/swift-evolution
>
> --
> Dave
>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160405/7750b1d7/attachment.html>