Add intersections and unions to Set

Tab Atkins Jr. jackalmage at
Mon Mar 4 10:56:48 PST 2013

On Mon, Mar 4, 2013 at 10:08 AM,  <aleth at> wrote:
> It would be useful to be able to form the intersection and the union of
> two Sets. These are natural operations that are currently not part of
> the API
> (
> Similar methods would make sense for Map, but one would have to think
> about what to do in the case where the key but not the value matches.
> An intersection is equivalent to a particular filter, so an alternative
> might be to add a method like Array.filter to Sets instead.
> (I filed bug 847355 for this and was told this mailing list was the
> right place for this suggestion.)

Yes please, and also minus (remove from set A all elements it shares
with set B).  All three of these are fairly vital for a lot of code
using sets.


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