Is there a Scala equivalent of EnumSet/EnumMap?

Question

In Java we have two nice classes: EnumSet for sets of enums and EnumMap for a map whose keys are enums. EnumSet is represented as a 64-bit word (or an array of 64-bit words) and EnumMap as an array of values, both indexed by the ordinal numbers of enums. So insert/lookup/remove/... operations take just O(1) time.

Do we have something like that in Scala - mutable or immutable?

I found BitSet (both mutable and immutable) which operates on integers, so I assumed there would be an efficient implementation of sets of Enumeration.Values backed up by it. But I found only Enumeration.ValueSet, which is backed up by SortedSet[Int]. While that's not so bad, BitSet seems to be quite more efficient for this purpose.

I didn't find any optimized implementation of maps with Enumeration.Value as keys similar to EnumMap.

Unlike Java `enum`s, Scala's `Enumeration` values can have arbitrary numerical identifiers and that is why I suspect there is no direct equivalent for Java `EnumSet` and `EnumMap` in Scala. — ghik, Nov 17 '12 at 19:01
@ghik While that's true I'd say this feature is rarely used. And when someone'd assign big numbers to values it'd be his responsibility to simply use a different `Set`/`Map` implementation. — Petr, Nov 17 '12 at 20:14

score 5 · Accepted Answer · edited Feb 26 '18 at 06:30

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Actually, in 2.10 Enumeration.ValueSet uses BitSet.

class ValueSet private[ValueSet] (private[this] var nnIds: immutable.BitSet)

That would be here.

edited Feb 26 '18 at 06:30

Roger

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answered Nov 17 '12 at 21:28

som-snytt

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Is there also an `EnumMap` equivalent? – Petr Feb 03 '13 at 13:42

Is there a Scala equivalent of EnumSet/EnumMap?

1 Answers1