[swift-users] 2 x lazy collection bugs

[Jens Alfke]

> On Feb 8, 2016, at 9:28 PM, Howard Lovatt via swift-users <swift-users at swift.org> wrote:
> 
> Not sure where it says that it won't be sequential - do you have a reference? 
…
> Not sure where it says it can be called more than one - the filter might be a very expensive operation like a database lookup!

I think it’s more that the documentation doesn’t specify sequential ordering, and that it doesn’t say the closure is only called once … so you can’t assume that those conditions are true. You’re just inferring that they are, based on your intuition about the implementation.

—Jens
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