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Mutable BitSet does not provide efficient logical operations #5513

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scabug opened this issue Feb 22, 2012 · 9 comments
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Mutable BitSet does not provide efficient logical operations #5513

scabug opened this issue Feb 22, 2012 · 9 comments
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enhancement help wanted library:collections
Milestone
2.13.0

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@scabug
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scabug commented Feb 22, 2012

The mutable BitSet does not expose mutating efficient logical operations like or, and, xor, and so on taking another BitSet.

I think those methods are an essential part of using mutable BitSets.
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scabug commented Feb 22, 2012

Imported From: https://issues.scala-lang.org/browse/SI-5513?orig=1
Reporter: ziggystar
Affected Versions: 2.9.1

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scabug commented Feb 29, 2012

Christopher Sahnwaldt (jcsahnwaldt) said:
I agree. Please have a good look at java.util.BitSet and add methods like set(from: Int, to: Int) and so on, which are necessary for efficient 'batch' operations. Thanks!

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scabug commented Mar 27, 2012

@adriaanm said:
We're happy to take pull requests for this! Unfortunately we do not have the resources to do this ourselves.

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scabug commented Mar 27, 2012

Igor Petruk (igor-petruk) said:
I've looked at BitSetLike. I does copying of all bits, plus it does so two times on each operation. I can play with trying to implement it with Vector instead of Array and see what loss/win we have

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scabug commented Mar 20, 2013

@JamesIry said:
scala/scala#2235

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scabug commented Dec 8, 2013

Denis Petrov (denis) said (edited on Dec 8, 2013 8:20:42 PM UTC):
In the current implementation mutable BitSet is required on the right hand side of those logical operations.
In code like set1 |= set2 both sets have to be mutable, although set2 does not have to be mutable to perform the operation.

@plokhotnyuk
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plokhotnyuk commented Jul 29, 2019 •
edited

It works as expected in Scala 2.13.0 and implemented more less efficiently by direct accessing to underlying arrays of bit words:

$ scala
Welcome to Scala 2.13.0 (OpenJDK 64-Bit GraalVM CE 19.1.1, Java 1.8.0_222).
Type in expressions for evaluation. Or try :help.

scala> import scala.collection.mutable
import scala.collection.mutable

scala> import scala.collection.immutable
import scala.collection.immutable

scala> val m = mutable.BitSet(1, 2, 3, 7)
m: scala.collection.mutable.BitSet = BitSet(1, 2, 3, 7)

scala> val i = immutable.BitSet(2, 3, 6)
i: scala.collection.immutable.BitSet = BitSet(2, 3, 6)

scala> m |= i
res0: m.type = BitSet(1, 2, 3, 6, 7)

scala> m ^= i
res1: m.type = BitSet(1, 7)

scala> m &= i
res2: m.type = BitSet()

It affects only Scala 2.12 or less:

$ /opt/scala-2.12.8/bin/scala
Welcome to Scala 2.12.8 (OpenJDK 64-Bit GraalVM CE 19.1.1, Java 1.8.0_222).
Type in expressions for evaluation. Or try :help.

scala> import scala.collection.mutable
import scala.collection.mutable

scala> import scala.collection.immutable
import scala.collection.immutable

scala> val m = mutable.BitSet(1, 2, 3, 7)
m: scala.collection.mutable.BitSet = BitSet(1, 2, 3, 7)

scala> val i = immutable.BitSet(2, 3, 6)
i: scala.collection.immutable.BitSet = BitSet(2, 3, 6)

scala> m |= i
<console>:16: error: type mismatch;
 found   : BitSet (in scala.collection.immutable)
 required: BitSet (in scala.collection.mutable)
       m |= i
            ^

Shouldn't the issue be closed as fixed?

@SethTisue SethTisue added this to the 2.13.0 milestone Jul 29, 2019
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@joshlemer agree?

@joshlemer
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@SethTisue agree

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