> Am 06.04.2016 um 20:26 schrieb Erica Sadun via swift-evolution > <swift-evolution@swift.org>: > >>> On Apr 6, 2016, at 12:23 PM, Stephen Canon via swift-evolution >>> <swift-evolution@swift.org> wrote: >>> >>> >>>> On Apr 6, 2016, at 11:20 AM, Stephen Canon via swift-evolution >>>> <swift-evolution@swift.org> wrote: >>>> >>>> On Apr 6, 2016, at 11:16 AM, Dave Abrahams via swift-evolution >>>> <swift-evolution@swift.org> wrote: >>>> >>>> One question that I *do* think we should answer, is whether the elements >>>> of >>>> >>>> (0..<199).striding(by: -2) >>>> >>>> are even or odd. >>> >>> Odd. I don’t believe that many real use cases care, but odd is more >>> efficient from a performance perspective. Needs to be documented clearly, >>> however. >> >> Sorry, I was thinking of (0…199).striding(by: -2). >> >> For the (0..<199) case, Erica’s assessment seems about right, though it >> isn’t at all obvious how it generalizes to floating point strides. > > (l..<h).striding(by: -dX) is undefined for floating point strides as there > cannot be a starting value.
Why? The starting value could quite naturally be s = l + k*dX for the largest value of k in the natural numbers for which s < h, wouldn't it? -Thorsten
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