on Tue Apr 05 2016, Howard Lovatt <swift-evolution@swift.org> wrote:
> Yes I know what you are saying and I am suggesting changing that so that: > > (0 ... -9) and (0 ..< -10) > > Are both empty ranges rather than errors because they implicitly have a 'by' > of > 1. What are the startIndex and endIndex of these ranges when viewed as Collections? Remember, for an empty collection startIndex == endIndex is an invariant. > > On Wednesday, 6 April 2016, Xiaodi Wu > <xiaodi...@gmail.com> wrote: > > Howard, the point I am raising is that `0...(-9)` is not valid Swift > because > the first, "lower" bound is enforced to be less than the second, "upper" > bound. > > The problem is that with that restriction certain types of half-open > intervals, namely those where the lower bound is the one being excluded, > cannot be represented as a Range either currently or in Dave A's branch. > > On Tue, Apr 5, 2016 at 3:30 PM Howard Lovatt > <howard.lov...@gmail.com> wrote: > > I much prefer (0 ... -9).by(-1) and (0 ..< -10).by(-1) > > On Wednesday, 6 April 2016, Dave Abrahams via swift-evolution > <swift-evolution@swift.org> 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 > <dabrah...@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@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution > > -- > -- Howard. -- Dave _______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
