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linasmlinasm
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Add shift operations to BitSet
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‎README.md‎

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@@ -41,6 +41,9 @@ The following operations are provided:
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- `Map`
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- [`zipByKey`](https://static.javadoc.io/org.scala-lang.modules/scala-collection-contrib_2.13/0.1.0/scala/collection/decorators/MapDecorator.html#zipByKey[W,That]\(other:scala.collection.Map[MapDecorator.this.map.K,W]\)\(implicitbf:scala.collection.BuildFrom[C,\(MapDecorator.this.map.K,\(MapDecorator.this.map.V,W\)\),That]\):That) / [`join`](https://static.javadoc.io/org.scala-lang.modules/scala-collection-contrib_2.13/0.1.0/scala/collection/decorators/MapDecorator.html#join[W,That]\(other:scala.collection.Map[MapDecorator.this.map.K,W]\)\(implicitbf:scala.collection.BuildFrom[C,\(MapDecorator.this.map.K,\(MapDecorator.this.map.V,W\)\),That]\):That) / [`zipByKeyWith`](https://static.javadoc.io/org.scala-lang.modules/scala-collection-contrib_2.13/0.1.0/scala/collection/decorators/MapDecorator.html#zipByKeyWith[W,X,That]\(other:scala.collection.Map[MapDecorator.this.map.K,W]\)\(f:\(MapDecorator.this.map.V,W\)=>X\)\(implicitbf:scala.collection.BuildFrom[C,\(MapDecorator.this.map.K,X\),That]\):That)
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- [`mergeByKey`](https://static.javadoc.io/org.scala-lang.modules/scala-collection-contrib_2.13/0.1.0/scala/collection/decorators/MapDecorator.html#mergeByKey[W,That]\(other:scala.collection.Map[MapDecorator.this.map.K,W]\)\(implicitbf:scala.collection.BuildFrom[C,\(MapDecorator.this.map.K,\(Option[MapDecorator.this.map.V],Option[W]\)\),That]\):That) / [`fullOuterJoin`](https://static.javadoc.io/org.scala-lang.modules/scala-collection-contrib_2.13/0.1.0/scala/collection/decorators/MapDecorator.html#fullOuterJoin[W,That]\(other:scala.collection.Map[MapDecorator.this.map.K,W]\)\(implicitbf:scala.collection.BuildFrom[C,\(MapDecorator.this.map.K,\(Option[MapDecorator.this.map.V],Option[W]\)\),That]\):That) / [`mergeByKeyWith`](https://static.javadoc.io/org.scala-lang.modules/scala-collection-contrib_2.13/0.1.0/scala/collection/decorators/MapDecorator.html#mergeByKeyWith[W,X,That]\(other:scala.collection.Map[MapDecorator.this.map.K,W]\)\(f:PartialFunction[\(Option[MapDecorator.this.map.V],Option[W]\),X]\)\(implicitbf:scala.collection.BuildFrom[C,\(MapDecorator.this.map.K,X\),That]\):That) / [`leftOuterJoin`](https://static.javadoc.io/org.scala-lang.modules/scala-collection-contrib_2.13/0.1.0/scala/collection/decorators/MapDecorator.html#leftOuterJoin[W,That]\(other:scala.collection.Map[MapDecorator.this.map.K,W]\)\(implicitbf:scala.collection.BuildFrom[C,\(MapDecorator.this.map.K,\(MapDecorator.this.map.V,Option[W]\)\),That]\):That) / [`rightOuterJoin`](https://static.javadoc.io/org.scala-lang.modules/scala-collection-contrib_2.13/0.1.0/scala/collection/decorators/MapDecorator.html#rightOuterJoin[W,That]\(other:scala.collection.Map[MapDecorator.this.map.K,W]\)\(implicitbf:scala.collection.BuildFrom[C,\(MapDecorator.this.map.K,\(Option[MapDecorator.this.map.V],W\)\),That]\):That)
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- `BitSet`
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- [`<<`](https://static.javadoc.io/org.scala-lang.modules/scala-collection-contrib_2.13/0.1.0/scala/collection/decorators/BitSetDecorator.html)
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- [`>>`](https://static.javadoc.io/org.scala-lang.modules/scala-collection-contrib_2.13/0.1.0/scala/collection/decorators/BitSetDecorator.html)
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## Maintenance status
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‎src/main/scala/scala/collection/decorators/BitSetDecorator.scala‎

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package scala.collection.decorators
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import scala.collection.{BitSet, BitSetOps}
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class BitSetDecorator[+C <: BitSet with BitSetOps[C]](protected val bs: C) {
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import BitSetDecorator._
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import BitSetOps._
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/**
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* Bitwise left shift of this BitSet by given the shift distance.
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* The shift distance may be negative, in which case this method performs a right shift.
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* @param shiftBy shift distance, in bits
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* @return a new BitSet whose value is a bitwise shift left of this BitSet by given shift distance (`shiftBy`)
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*/
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def <<(shiftBy: Int): C = {
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val shiftedBits = if (shiftBy > 0) shiftLeft(shiftBy)
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else if (shiftBy == 0) bs.toBitMask
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else shiftRight(-shiftBy)
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bs.fromBitMaskNoCopy(shiftedBits)
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}
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/**
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* Bitwise right shift of this BitSet by the given shift distance.
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* The shift distance may be negative, in which case this method performs a left shift.
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* @param shiftBy shift distance, in bits
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* @return a new BitSet whose value is a bitwise shift right of this BitSet by given shift distance (`shiftBy`)
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*/
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def >>(shiftBy: Int): C = {
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val shiftedBits = if (shiftBy > 0) shiftRight(shiftBy)
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else if (shiftBy == 0) bs.toBitMask
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else shiftLeft(-shiftBy)
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bs.fromBitMaskNoCopy(shiftedBits)
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}
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private def shiftLeft(shiftBy: Int): Array[Long] = {
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val bitOffset = shiftBy & WordMask
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val wordOffset = shiftBy >>> LogWL
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if (bitOffset == 0) {
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val newSize = bs.nwords + wordOffset
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require(newSize <= MaxSize)
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val newBits = Array.ofDim[Long](newSize)
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var i = wordOffset
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while (i < newSize) {
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newBits(i) = bs.word(i - wordOffset)
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i += 1
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}
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newBits
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} else {
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val revBitOffset = WordLength - bitOffset
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val extraBits = bs.word(bs.nwords - 1) >>> revBitOffset
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val extraWordCount = if (extraBits == 0) 0 else 1
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val newSize = bs.nwords + wordOffset + extraWordCount
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require(newSize <= MaxSize)
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val newBits = Array.ofDim[Long](newSize)
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var previous = 0L
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var i = 0
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while (i < bs.nwords) {
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val current = bs.word(i)
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newBits(i + wordOffset) = (previous >>> revBitOffset) | (current << bitOffset)
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previous = current
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i += 1
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}
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if (extraWordCount != 0) newBits(newSize - 1) = extraBits
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newBits
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}
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}
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private def shiftRight(shiftBy: Int): Array[Long] = {
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val bitOffset = shiftBy & WordMask
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if (bitOffset == 0) {
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val wordOffset = shiftBy >>> LogWL
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val newSize = bs.nwords - wordOffset
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if (newSize > 0) {
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val newBits = Array.ofDim[Long](newSize)
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var i = 0
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while (i < newSize) {
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newBits(i) = bs.word(i + wordOffset)
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i += 1
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}
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newBits
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} else Array.emptyLongArray
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} else {
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val wordOffset = (shiftBy >>> LogWL) + 1
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val extraBits = bs.word(bs.nwords - 1) >>> bitOffset
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val extraWordCount = if (extraBits == 0) 0 else 1
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val newSize = bs.nwords - wordOffset + extraWordCount
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if (newSize > 0) {
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val revBitOffset = WordLength - bitOffset
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val newBits = Array.ofDim[Long](newSize)
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var previous = bs.word(wordOffset - 1)
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var i = wordOffset
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while (i < bs.nwords) {
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val current = bs.word(i)
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newBits(i - wordOffset) = (previous >>> bitOffset) | (current << revBitOffset)
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previous = current
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i += 1
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}
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if (extraWordCount != 0) newBits(newSize - 1) = extraBits
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newBits
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} else Array.emptyLongArray
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}
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}
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}
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object BitSetDecorator {
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private[collection] final val WordMask = BitSetOps.WordLength - 1
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}

‎src/main/scala/scala/collection/decorators/package.scala‎

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@@ -17,4 +17,7 @@ package object decorators {
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implicit def MapDecorator[C](coll: C)(implicit map: IsMap[C]): MapDecorator[C, map.type] =
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new MapDecorator(coll)(map)
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implicit def bitSetDecorator[C <: BitSet with BitSetOps[C]](bs: C): BitSetDecorator[C] =
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new BitSetDecorator(bs)
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}

‎src/test/scala/scala/collection/decorators/BitSetDecoratorTest.scala‎

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package scala.collection.decorators
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import org.junit.{Assert, Test}
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import scala.collection.BitSet
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class BitSetDecoratorTest {
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import Assert.assertEquals
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import BitSet.empty
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@Test
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def shiftEmptyLeft(): Unit = {
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for (shiftBy <- 0 to 128) {
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assertEquals(empty, empty << shiftBy)
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}
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}
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@Test
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def shiftLowestBitLeft(): Unit = {
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for (shiftBy <- 0 to 128) {
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assertEquals(BitSet(shiftBy), BitSet(0) << shiftBy)
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}
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}
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@Test
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def shiftNegativeLeft(): Unit = {
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assertEquals(BitSet(0), BitSet(1) << -1)
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}
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@Test
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def largeShiftLeft(): Unit = {
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val bs = BitSet(0 to 300 by 5: _*)
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for (shiftBy <- 0 to 128) {
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assertEquals(bs.map(_ + shiftBy), bs << shiftBy)
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}
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}
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@Test
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def shiftEmptyRight(): Unit = {
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for (shiftBy <- 0 to 128) {
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assertEquals(empty, empty >> shiftBy)
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}
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}
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@Test
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def shiftLowestBitRight(): Unit = {
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assertEquals(BitSet(0), BitSet(0) >> 0)
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for (shiftBy <- 1 to 128) {
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assertEquals(empty, BitSet(0) >> shiftBy)
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}
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}
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@Test
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def shiftToLowestBitRight(): Unit = {
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for (shiftBy <- 0 to 128) {
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assertEquals(BitSet(0), BitSet(shiftBy) >> shiftBy)
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}
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}
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@Test
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def shiftNegativeRight(): Unit = {
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assertEquals(BitSet(1), BitSet(0) >> -1)
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}
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@Test
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def largeShiftRight(): Unit = {
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val bs = BitSet(0 to 300 by 5: _*)
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for (shiftBy <- 0 to 128) {
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assertEquals(bs.collect {
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case b if b >= shiftBy => b - shiftBy
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}, bs >> shiftBy)
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}
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}
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}

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