[swift-evolution] zip3, zip4, ...

[Davide De Franceschi]

Yes, it would, but you also need the ZipSequence to be able to support that, which would actually need variadic generics. Which aren't supported :)

> On 7 Dec 2015, at 13:12, Vinicius Vendramini via swift-evolution <swift-evolution at swift.org> wrote:
> 
> I wouldn't really know how to do this, but a better approach than implementing zip2 through zip10 might be making it a variadic function, no?
> 
> On Dec 6, 2015, at 6:49 PM, Donnacha Oisín Kidney via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> 
>> An implementation of this is actually pretty complicated, since you aren’t supposed to call a generator once it’s returned nil.
>> 
>> public struct NilPaddedZipGenerator<G0: GeneratorType, G1: GeneratorType> : GeneratorType {
>>   
>>   private var (g0, g1): (G0?, G1?)
>>   
>>   public mutating func next() -> (G0.Element?, G1.Element?)? {
>>     let (e0,e1) = (g0?.next(),g1?.next())
>>     switch (e0,e1) {
>>     case (nil,nil): return nil
>>     case (  _,nil): g1 = nil
>>     case (nil,  _): g0 = nil
>>     default: break
>>     }
>>     return (e0,e1)
>>   }
>> }
>> 
>> public struct NilPaddedZip<S0: SequenceType, S1: SequenceType> : LazySequenceType {
>>   
>>   private let (s0, s1): (S0, S1)
>>   public func generate() -> NilPaddedZipGenerator<S0.Generator, S1.Generator> {
>>     return NilPaddedZipGenerator(g0: s0.generate(), g1: s1.generate())
>>   }
>> }
>> 
>> @warn_unused_result
>> public func zipWithPadding<S0: SequenceType, S1: SequenceType>(s0: S0, _ s1: S1)
>>   -> NilPaddedZip<S0, S1> {
>>     return NilPaddedZip(s0: s0, s1: s1)
>> }
>> 
>>> On 6 Dec 2015, at 23:44, Erica Sadun via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>> Is there an implementation in the stdlib for (T?, T?) like this?
>>> 
>>>> On Dec 6, 2015, at 4:37 PM, Dmitri Gribenko <gribozavr at gmail.com <mailto:gribozavr at gmail.com>> wrote:
>>>> 
>>>> On Sun, Dec 6, 2015 at 3:34 PM, Erica Sadun via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>> It's pretty easy to build your own Zips. Not sure the language really needs this. For example, I recently built a zip that produces (T?, T?) which fills one of the two with nil until both lists are consumed:
>>>> 
>>>> func longZip<S0: SequenceType, S1: SequenceType>(seq0: S0, _ seq1: S1) ->
>>>>     AnyGenerator<(S0.Generator.Element?, S1.Generator.Element?)> {
>>>> 
>>>> 
>>>> Just wanted to point out that AnyGenerator has an inherent cost from the type erasure.  The implementation in the standard library uses generics and is fully optimizable.
>>>> 
>>>> Dmitri
>>>> 
>>>> -- 
>>>> main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if
>>>> (j){printf("%d\n",i);}}} /*Dmitri Gribenko <gribozavr at gmail.com <mailto:gribozavr at gmail.com>>*/
>>> 
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