Add intersections and unions to Set

Peter Michaux petermichaux at
Fri Mar 29 22:23:01 PDT 2013

On Mon, Mar 4, 2013 at 10:56 AM, Tab Atkins Jr. <jackalmage at> wrote:
> 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.

I agree that these methods would be useful. They are common set
operations and they do seem missing from the Set draft spec.


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