Question

Currently I use this to pick the first element of a list:

   def Get_Read_Key =
   {
      logger.entering (TAG, "Get_Read_Key")

      val Retval = if (Read_Key_Available)
      {
         val Retval = Keystrokes.head

         Keystrokes = Keystrokes.tail

         Retval
      }
      else
      {
         calculator.ui.IKey.No_Key
      } // if

      logger.exiting (TAG, "Get_Read_Key", Retval)
          Retval
   } // Get_Read_Key

   def Read_Key_Available = Keystrokes.size > 0

But it looks all kind of clumsy — especially the double ´Retval´. Is there a better way of doing this? Or is it just the price to pay for using an immutable list?

Background: The routine is used on a Unit Test Mock class – return types are set.

Answer 1

You’re implementing an Iterator on a List, that’s already in the standard library.

val it = Keystrokes.iterator
def Read_Key_Available = it.hasNext
def Get_Read_Key = if(it.hasNext) it.next() else calculator.ui.IKey.No_Key