Suggestions for Set

Brendan Eich brendan at
Wed Oct 3 08:07:28 PDT 2012

Dean Landolt wrote:
> On Wed, Oct 3, 2012 at 3:47 AM, Jussi Kalliokoski 
> <jussi.kalliokoski at <mailto:jussi.kalliokoski at>> wrote:
>     On Wed, Oct 3, 2012 at 10:24 AM, Andreas Rossberg
>     <rossberg at <mailto:rossberg at>> wrote:
>         On 3 October 2012 05:38, Brendan Eich <brendan at
>         <mailto:brendan at>> wrote:
>         > Which is more important, iterating over holes (preserved if
>         possible), or
>         > skipping them and therefore spreading array-likes but not
>         iterables?
>         I, for one, couldn't care less about holes. We shouldn't
>         compromise
>         any useful feature just for the sake of preserving some array hole
>         craziness.
>     I agree. Unless there's a sane use case for holes with the spread
>     operator, I don't think it makes sense to make compromises because
>     of them, especially since we aren't breaking backwards
>     compatibility or anything. We can actually make something better here.
> I seem to remember an issue re: what to do with infinite iterators 
> (generators)? If that's correct, was there an agreed-upon resolution?

This is just a D.o.S. hazard that engines must defend against with 
memory and time-based watchdogs. Even if spread considered only 
array-like types and not iterables first, a huge array or lying proxy 
could DoS it. Separate concern, dealt with generically.


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