on Thu Jun 30 2016, Haravikk <swift-evolution-AT-haravikk.me> wrote:
>> On 30 Jun 2016, at 18:26, Dave Abrahams <dabrah...@apple.com> wrote: >> >> Q: Why should there be indices on an infinite multipass sequence? >> A: Because the operations on indices apply equally well whether the >> sequence is finite or not. Find the index of a value in the >> sequence, slice the sequence, find again, etc. > > Would it not make more sense for sequences that can benefit from > subscripts to just conform to Indexable? All multi-pass sequences can benefit from subscripts. > It seems like having basically all of the Collection-specific methods > on Sequence too would be confusing, and dilute any nothing that these > are sequences where elements are supposed to be consumed in-order, as > it would give the illusion that you can skip around with the > convenience of an array. If traversal consumes the sequence, it is a single-pass thing. > There's also the issue of how you would even index something that's > potentially infinite; you'd need to use a big integer in which case > you could end up with your indices growing to infinite size over time? It's trivial; the index contains the iteration state. The only fundamental difference between the constraints on Iterator and the constraints on an Index is that Iterator doesn't support comparison for equality. -- Dave _______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
