[swift-evolution] [RFC] New collections model: collections advance indices

[Károly Lőrentey]

On 2016-03-08 15:09:35 +0000, Károly Lőrentey via swift-evolution said:

> My problem is that this example assumes that mutating `c` at a certain
> index won't invalidate earlier indices. And even if that is true for
> `c`, whenever `c.indices` holds a strong reference, an idiom like
> 
>   for i in c.indices {
>     c.mutate(i)
>   }
> 
> will certainly lead to COW copying that isn't happening today with
> 
>   var i = c.startIndex
>   while i != c.endIndex {
>     c.mutate(i)
>     i = i.successor()
>   }
> 
> How would I emulate the exact semantics of today's code with `c.indices`?

Sorry, I guess that second code should read

  var i = c.startIndex
  let end = c.endIndex
  while i != end {
    c.mutate(i)
    i = i.successor()
  }

I think it would be interesting to see the `c.indices` versions of both 
variants, though.

-- 
Károly