[swift-users] Why does RangeReplaceableCollection require an empty initialiser?

[Tim Vermeulen]

I’m not allowing generic subscripts. The collection is declared as `AnyIndexArray<Index: Strideable, Element where Index.Stride == Int>` and it can be subscripted with type `Index`.

Either way, it’s not really important. I’m mostly wondering why RangeReplaceableCollection needs an empty initialiser.

> Then how you defined the index to conform toStrideable? Below code does work as it seams that you can't use generics in subscripts.
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> subscript<T:Strideable>(index:T) ->Element
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> Zhaoxin
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> On Wed, Jul 6, 2016 at 8:32 PM, Tim Vermeulen<tvermeulen at me.com(mailto:tvermeulen at me.com)>wrote:
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> > > On 6 Jul 2016, at 14:03, Zhao Xin<owenzx at gmail.com(mailto:owenzx at gmail.com)>wrote:
> > > According to the document of Swift 3, Array has already conformed protocolRangeReplaceableCollection.
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> > That’s exactly why I also want to conform my wrapper to that protocol? I think there’s a misunderstanding. I’m making a collection that can be subscripted with any index (that conforms to Strideable), but behaves like an array otherwise.
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> > > Zhaoxin
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> > > On Wed, Jul 6, 2016 at 7:09 PM, Tim Vermeulen via swift-users<swift-users at swift.org(mailto:swift-users at swift.org)>wrote:
> > > > RangeReplaceableCollection has three initialisers: init(), init(_:) and init(repeating:count:). The latter two are implemented using the empty initialiser. But why are these initialisers part of this particular protocol? As far as I can tell, no other methods of this protocol depend on these initialisers. The requirement of the empty initialiser makes it impossible to have a collection conform to this protocol that needs additional data for its initialisation.
> > > > 
> > > > For instance, I was making an array that works with any Strideable indices, not just integers. A startIndex is needed for its initialisation, so I can’t really conform it to RangeReplaceableCollection. If I do it anyways (with a fatalError() in the required empty initialiser) everything seems to work just fine, except for the protocol’s three initialisers.
> > > > 
> > > > Perhaps these initialisers should be moved to a (possible new) different protocol?
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> > > 
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