[swift-evolution] [Pitch] Remove destructive consumption from Sequence

[Brent Royal-Gordon]

> On Jul 1, 2016, at 12:34 AM, Haravikk <swift-evolution at haravikk.me> wrote:
> 
> Sequences are currently dead easy to implement, and to implement in an ad-hoc way via AnySequence(body:), how would that be done under this required indexing scheme?

`sequence(state:next:)` could be adapted into a possibly-infinite `Collection`, and it's not much more difficult to use than `AnySequence`. (Although it would be more efficient to use a custom iterator for it than it would be to iterate with its indices.)

-- 
Brent Royal-Gordon
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