on Wed Apr 06 2016, Erica Sadun <erica-AT-ericasadun.com> wrote: > On Apr 6, 2016, at 3:05 PM, Dave Abrahams via swift-evolution > <[email protected]> wrote: > > on Wed Apr 06 2016, Xiaodi Wu <xiaodi.wu-AT-gmail.com> wrote: > > On Wed, Apr 6, 2016 at 3:28 PM, Dave Abrahams via swift-evolution > <[email protected]> wrote: > > You if you need to represent `<..` intervals in scientific computing, > that's a pretty compelling argument for supporting them. > > I'd like to be able to represent any of those as > Intervals-which-are-now-Ranges. It makes sense to do so > because > the > things I want to do with them, such as clamping and testing if > some > value is contained, are exactly what Intervals-now-Ranges > provide. > Looking around, it seems many other languages provide only > what > Swift > currently does, but Perl does provide `..`, `..^`, `^..`, and > `^..^` > (which, brought over to Swift, would be `...`, `..<`, `<..`, > and > `<.<`). > > Do we need fully-open ranges too? > > I haven't encountered a need for open ranges, but I would expect that > other applications in scientific computing could make use of them. > I rather like Pyry's suggestions below. > > Below? > > Logically in time below.
Oh! In my application, time flows downward. > > I believe the following is a valid conversion of the Xiaodi Wu below into the > Dave A domain. > > On Apr 6, 2016, at 2:29 PM, Pyry Jahkola via swift-evolution > <[email protected]> wrote: > > I think a sensible specification would be that with a positive step size, > the count starts from the lower bound, and with a negative one, it starts > from the upper bound (inclusive or exclusive). Thus, the following > examples > should cover all the corner cases: > > (0 ... 9).striding(by: 2) == [0, 2, 4, 6, 8] > (0 ..< 9).striding(by: 2) == [0, 2, 4, 6, 8] > (0 <.. 9).striding(by: 2) == [2, 4, 6, 8] > (0 <.< 9).striding(by: 2) == [2, 4, 6, 8] > > (0 ... 9).striding(by: 3) == [0, 3, 6, 9] > (0 ..< 9).striding(by: 3) == [0, 3, 6] > (0 <.. 9).striding(by: 3) == [3, 6, 9] > (0 <.< 9).striding(by: 3) == [3, 6] > > (0 ... 9).striding(by: -2) == [9, 7, 5, 3, 1] > (0 ..< 9).striding(by: -2) == [7, 5, 3, 1] > (0 <.. 9).striding(by: -2) == [9, 7, 5, 3, 1] > (0 <.< 9).striding(by: -2) == [7, 5, 3, 1] > > (0 ... 9).striding(by: -3) == [9, 6, 3, 0] > (0 ..< 9).striding(by: -3) == [6, 3, 0] > (0 <.. 9).striding(by: -3) == [9, 6, 3] > (0 <.< 9).striding(by: -3) == [6, 3] These all look reasonable to me. > Lastly, if you want the positive stride reversed, you'd do just that: > > (0 ... 9).striding(by: 2).reverse() == [8, 6, 4, 2, 0] Also reasonable. -- Dave _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution
