ScalaのInt型でビットを扱う

BitVal.scala

object BitVal {

  implicit class BitInt(val self: Int) extends AnyVal {
    @inline
    def on(place: Int): Int = self | (1 << place)

    @inline
    def off(place: Int): Int = self & ~(1 << place)

    @inline
    def countOn(): Int = {
      var count = 0
      var _self = self
      while (_self > 0) {
        count += _self & 1
        _self >>= 1
      }
      count
    }

    @inline
    def countOff(): Int = 32 - countOn()

    @inline
    def toBitString(): String = {
      val sb = new StringBuilder()
      sb.append("0b")
      for (figure <- 31 to 0 by -1) {
        val bitChar = self & 1 << figure match {
          case 0 => '0'
          case _ => '1'
        }
        sb.append(bitChar)
      }
      sb.toString()
    }
  }

  def main(args: Array[String]): Unit = {
    val a = 1234
    assert(a.on(2) == 1238)
    assert(a == a.on(2).off(2))
    assert(a.countOn() == 5)
    assert(a.countOff() == 27)
    assert(a.toBitString() == "0b00000000000000000000010011010010")
  }
}