on Mon Apr 11 2016, Ross O'Brien <swift-evolution at swift.org> wrote:
> I think I'd like to +1 a 'for x in loop(from: while: next:)'. (Possibly
> 'iterate' rather than 'loop'?)
Maybe 'iterations'. It should be a noun, I think.
> I've not missed the C-style for-loop so I've not argued to keep it, but recently
> I was refactoring a function which started with a UIView and iterated up the
> hierarchy through the superview property, and it occurred to me recently that
> neither stride nor sequences/generators handle recursive iterations well.
>
> So, I imagine that would look like this:
> for view in loop(from: startingSubview, while: { $0 != nil }, next: { $0 =
> $0.superview })
>
> On Mon, Apr 11, 2016 at 11:31 PM, Dave Abrahams via swift-evolution
> <swift-evolution at swift.org> wrote:
>
> on Mon Apr 11 2016, Michel Fortin <michel.fortin-AT-michelf.ca> wrote:
>
> > Le 11 avr. 2016 à 14:36, Dave Abrahams
> <dabrahams at apple.com> a écrit :
> >
> >> 3. The fact that we're migrating C-style for loops to
> >> uses of stride, as noted in https://github.com/apple/swift/pull/2125,
> >> has convinced me that, sadly, we may need an answer that doesn't
> >> involve ranges. But maybe something like
> >>
> >> for x in loop(from: 0.1, while: { $0 < 10 }, next: { $0 + .2 })
> >>
> >> is sufficient for this purpose.
> >
> > Please add that.
>
> Please write a proposal and ideally, submit a patch :-).
>
> Seriously, if this is something you believe in, we could really use the
> help.
>
> > First, it would relieve `stride` from some of the pressure of
> > excelling at replacing existing C-style for loops. But it would also
> > become pretty easy to write custom sequences like this one:
> >
> > func uniform(start: Double, end: Double, numberOfSteps totalSteps: Int) ->
> Sequence {
> > var currentStep = 0
> > return loop(from: start, while: { _ in
> > currentStep < totalSteps
> > }, next: { _ in
> > currentStep += 1
> > return start * (Double(totalSteps-currentStep) / Double(totalSteps)) +
> > end * (Double(currentStep) / Double(totalSteps))
> > })
> > }
>
> Aside from the fact that you can't return Sequence, this seems like a
> much better way to do that in Swift 3.0:
>
> func uniform(
> start: Double, end: Double, numberOfSteps totalSteps: Int
> ) -> LazyMapRandomAccessCollection<CountableRange<Int>, Double> {
> return (0..<totalSteps).lazy.map {
> start * (Double(totalSteps-$0) / Double(totalSteps)) +
> end * (Double($0) / Double(totalSteps))
> }
> }
>
> --
> Dave
>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
--
Dave