timeofday.scala

package examples

object timeofday {
  class DateError extends Exception

  /** Simulating properties in Scala 
   *  (example 4.2.1 in ScalaReference.pdf) 
   */
  class TimeOfDayVar {
    private var h, m, s: Int = 0

    def hours = h

    /** A method 'ident_=' is a setter for 'ident'. 'code.ident = ...' will 
     *  be translated to a call to 'ident_=' 
     */
    def hours_= (h: Int) =
      if (0 <= h && h < 24) this.h = h
      else throw new DateError()

    def minutes = m
    def minutes_= (m: Int) =
      if (0 <= m && m < 60) this.m = m
      else throw new DateError()

    def seconds = s
    def seconds_= (s: Int) =
      if (0 <= s && s < 60) this.s = s
      else throw new DateError()
  }
  
  def main(args: Array[String]) {
    val d = new TimeOfDayVar
    d.hours = 8; d.minutes = 30; d.seconds = 0
    d.hours = 25 // throws a DateError exception
  }
}