Scala example source code file (BitOperations.scala)

This example Scala source code file (BitOperations.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

bitoperations, int, long, string

The BitOperations.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package collection
package generic

/** Some bit operations.
 *
 *  See http://www.drmaciver.com/2008/08/unsigned-comparison-in-javascala/ for
 *  an explanation of unsignedCompare.
 */
private[collection] object BitOperations {
  trait Int {
    type Int = scala.Int
    def zero(i: Int, mask: Int)                 = (i & mask) == 0
    def mask(i: Int, mask: Int)                 = i & (complement(mask - 1) ^ mask)
    def hasMatch(key: Int, prefix: Int, m: Int) = mask(key, m) == prefix
    def unsignedCompare(i: Int, j: Int)         = (i < j) ^ (i < 0) ^ (j < 0)
    def shorter(m1: Int, m2: Int)               = unsignedCompare(m2, m1)
    def complement(i: Int)                      = (-1) ^ i
    def bits(num: Int)                          = 31 to 0 by -1 map (i => (num >>> i & 1) != 0)
    def bitString(num: Int, sep: String = "")   = bits(num) map (b => if (b) "1" else "0") mkString sep

    def highestOneBit(j: Int) = {
      var i = j
      i |= (i >>  1)
      i |= (i >>  2)
      i |= (i >>  4)
      i |= (i >>  8)
      i |= (i >> 16)
      i - (i >>> 1)
    }
  }
  object Int extends Int

  trait Long {
    type Long = scala.Long
    def zero(i: Long, mask: Long)                  = (i & mask) == 0L
    def mask(i: Long, mask: Long)                  = i & (complement(mask - 1) ^ mask)
    def hasMatch(key: Long, prefix: Long, m: Long) = mask(key, m) == prefix
    def unsignedCompare(i: Long, j: Long)          = (i < j) ^ (i < 0L) ^ (j < 0L)
    def shorter(m1: Long, m2: Long)                = unsignedCompare(m2, m1)
    def complement(i: Long)                        = (-1L) ^ i
    def bits(num: Long)                            = 63L to 0L by -1L map (i => (num >>> i & 1L) != 0L)
    def bitString(num: Long, sep: String = "")     = bits(num) map (b => if (b) "1" else "0") mkString sep

    def highestOneBit(j: Long) = {
      var i = j
      i |= (i >>  1)
      i |= (i >>  2)
      i |= (i >>  4)
      i |= (i >>  8)
      i |= (i >> 16)
      i |= (i >> 32)
      i - (i >>> 1)
    }
  }
  object Long extends Long
}