> On 7 févr. 2017, at 21:57, Slava Pestov <spes...@apple.com> wrote:
>
>>
>> On Feb 7, 2017, at 8:14 PM, Guillaume Lessard via swift-users
>> <swift-users@swift.org> wrote:
>>
>> I keep running into weird things with Swift 3 Collections.
>>
>> A) Collection has its count property defined as an Int via IndexDistance:
>>
>> public protocol Collection : Indexable, Sequence {
>> associatedtype IndexDistance : SignedInteger = Int // line 182 in
>> Collection.swift
>> public var count: IndexDistance { get } // line 776
>> }
>
> This declaration specifies that the *default* associated type is Int, not
> that it’s *always* Int. A Collection implementation is free to use a
> different type as its IndexDistance if it wants.
I see how I’d misunderstood that line.
This being said, does this particular freedom really bring anything to the
table? It is simply a counter (“the number of steps between a pair of
indices”). On one hand, a “collection" that has in excess of Int.max/2 elements
likely needs a different protocol; on the other, using a shorter type for a
counter seems retro.
Thanks!
Guillaume Lessard
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