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Scala example source code file (BitSetLike.scala)
The Scala BitSetLike.scala source code/* __ *\ ** ________ ___ / / ___ Scala API ** ** / __/ __// _ | / / / _ | (c) 2003-2011, LAMP/EPFL ** ** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ ** ** /____/\___/_/ |_/____/_/ | | ** ** |/ ** \* */ package scala.collection import BitSetLike._ import generic._ import mutable.StringBuilder /** A template trait for bitsets. * $bitsetinfo * * This trait provides most of the operations of a `BitSet` independently of its representation. * It is inherited by all concrete implementations of bitsets. * * @tparam This the type of the bitset itself. * * @define bitsetinfo * Bitsets are sets of non-negative integers which are represented as * variable-size arrays of bits packed into 64-bit words. The memory footprint of a bitset is * determined by the largest number stored in it. * @author Martin Odersky * @version 2.8 * @since 2.8 * @define coll bitset * @define Coll BitSet */ trait BitSetLike[+This <: BitSetLike[This] with Set[Int]] extends SetLike[Int, This] { self => def empty: This /** The number of words (each with 64 bits) making up the set */ protected def nwords: Int /** The words at index `idx', or 0L if outside the range of the set * '''Note:''' requires `idx >= 0` */ protected def word(idx: Int): Long /** Creates a new set of this kind from an array of longs */ protected def fromArray(elems: Array[Long]): This override def size: Int = { var s = 0 var i = nwords while (i > 0) { i -= 1 s += popCount(word(i)) } s } def iterator = new Iterator[Int] { private var current = 0 private val end = nwords * WordLength def hasNext: Boolean = { while (current < end && !self.contains(current)) current += 1 current < end } def next(): Int = if (hasNext) { val r = current; current += 1; r } else Iterator.empty.next } override def foreach[B](f: Int => B) { for (i <- 0 until nwords) { val w = word(i) for (j <- i * WordLength until (i + 1) * WordLength) { if ((w & (1L << j)) != 0L) f(j) } } } /** Computes the union between this bitset and another bitset by performing * a bitwise "or". * * @param other the bitset to form the union with. * @return a new bitset consisting of all bits that are in this * bitset or in the given bitset `other`. */ def | (other: BitSet): This = { val len = this.nwords max other.nwords val words = new Array[Long](len) for (idx <- 0 until len) words(idx) = this.word(idx) | other.word(idx) fromArray(words) } /** Computes the intersection between this bitset and another bitset by performing * a bitwise "and". * @param that the bitset to intersect with. * @return a new bitset consisting of all elements that are both in this * bitset and in the given bitset `other`. */ def & (other: BitSet): This = { val len = this.nwords min other.nwords val words = new Array[Long](len) for (idx <- 0 until len) words(idx) = this.word(idx) & other.word(idx) fromArray(words) } /** Computes the difference of this bitset and another bitset by performing * a bitwise "and-not". * * @param that the set of bits to exclude. * @return a bitset containing those bits of this * bitset that are not also contained in the given bitset `other`. */ def &~ (other: BitSet): This = { val len = this.nwords val words = new Array[Long](len) for (idx <- 0 until len) words(idx) = this.word(idx) & ~other.word(idx) fromArray(words) } /** Computes the symmetric difference of this bitset and another bitset by performing * a bitwise "exclusive-or". * * @param that the other bitset to take part in the symmetric difference. * @return a bitset containing those bits of this * bitset or the other bitset that are not contained in both bitsets. */ def ^ (other: BitSet): This = { val len = this.nwords max other.nwords val words = new Array[Long](len) for (idx <- 0 until len) words(idx) = this.word(idx) ^ other.word(idx) fromArray(words) } def contains(elem: Int): Boolean = 0 <= elem && (word(elem >> LogWL) & (1L << elem)) != 0L /** Tests whether this bitset is a subset of another bitset. * * @param that the bitset to test. * @return `true` if this bitset is a subset of `other`, i.e. if * every bit of this set is also an element in `other`. */ def subsetOf(other: BitSet): Boolean = (0 until nwords) forall (idx => (this.word(idx) & ~ other.word(idx)) == 0L) override def addString(sb: StringBuilder, start: String, sep: String, end: String) = { sb append start var pre = "" for (i <- 0 until nwords * WordLength) if (contains(i)) { sb append pre append i pre = sep } sb append end } override def stringPrefix = "BitSet" } /** Companion object for BitSets. Contains private data only */ object BitSetLike { private[collection] val LogWL = 6 private val WordLength = 64 private[collection] def updateArray(elems: Array[Long], idx: Int, w: Long): Array[Long] = { var len = elems.length while (len > 0 && (elems(len - 1) == 0L || w == 0L && idx == len - 1)) len -= 1 var newlen = len if (idx >= newlen && w != 0L) newlen = idx + 1 val newelems = new Array[Long](newlen) Array.copy(elems, 0, newelems, 0, len) if (idx < newlen) newelems(idx) = w else assert(w == 0L) newelems } private val pc1: Array[Int] = { def countBits(x: Int): Int = if (x == 0) 0 else x % 2 + countBits(x >>> 1) Array.tabulate(256)(countBits _) } private def popCount(w: Long): Int = { def pc2(w: Int) = if (w == 0) 0 else pc1(w & 0xff) + pc1(w >>> 8) def pc4(w: Int) = if (w == 0) 0 else pc2(w & 0xffff) + pc2(w >>> 16) if (w == 0L) 0 else pc4(w.toInt) + pc4((w >>> 32).toInt) } } Other Scala examples (source code examples)Here is a short list of links related to this Scala BitSetLike.scala source code file: |
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