CountingBits.scala

def countOneBits(l: Long) = {
  val Hex55 = 0x5555555555555555L
  val Hex33 = 0x3333333333333333L
  val Hex0F = 0x0F0F0F0F0F0F0F0FL
  val Hex01 = 0x0101010101010101L
  var x = l - ((l >> 1) & Hex55)
  x = (x & Hex33) + ((x >> 2) & Hex33)
  x = (x + (x >> 4)) & Hex0F
  (x * Hex01) >> 56
} 

def time[R](block: => R): (R, Long) = {  
  val t0 = System.currentTimeMillis()
  val result = block
  val t1 = System.currentTimeMillis()
  (result, t1 - t0)
}

// @ time { (0L to 1000000000).foldLeft(0L)((a,c) => a + countOneBits(c)) } 
// res98: (Long, Long) = (14846928141L, 31164L)