Scala for impatients, chapter 5, 2th task

gistfile1.scala

class Account {
  private var balance: Double = 0;

  def credit = if ( balance < 0 ) -balance else 0

  def credit_=( value: Int ) {
    balance = -value
  }

  def debit = if ( balance > 0 ) balance else 0

  def debit_=( value: Int ) {
    balance = value
  }
}

var myAccount = new Account()

myAccount.credit = 1
println( "debit" -> myAccount.debit, "credit" -> myAccount.credit )

myAccount.debit = 1
println( "debit" -> myAccount.debit, "credit" -> myAccount.credit )

myAccount.credit = -1
println( "debit" -> myAccount.debit, "credit" -> myAccount.credit )

myAccount.credit = 0
println( "debit" -> myAccount.debit, "credit" -> myAccount.credit )