Past exam of the year 1 of the computer science course of the University of Oxford / 2022 / Imperative programming (resit) / 6 / b / ii / Solution

Reuse the machinery with the digit interval:

trait DigitCountPlugIn extends CharCountPlugin {
  override protected def firstCounted: Char = '0'
  override protected def numberCounted: Int = 10
}

Its count precondition is now '0' <= ch && ch <= '9'. It counts digits while permitting all characters to be stored. This is an alternative configured counter, rather than a second independent lowercase counter in the same object; simultaneous independent alphabets would require separate counters or a combined mapping.