Scala - error when passing parameters

Question

I am doing the Martin Odersky course about Scala. In one of the assignments I have the following type:

type Occurrences = List[(Char, Int)]

I have defined a method which subtracts an element of type (Char, Int) from an element of type Occurrences.

  def subtractOne(x: Occurrences, (char: Char, nr: Int)): Occurrences = x match {
    case List() => throw new Exception("can not subtract")
    case (char, nr2) :: ocs => {
      if(nr2 > nr) (char, nr2 - nr) :: ocs
      else if(nr2 == nr) ocs
      else throw new Exception("can not subtract")
    }
    case _ :: ocs => subtractOne(ocs, (char, nr))
  }

However, I am getting some unclear errors on the first line: Wrong parameter and Definition or declaration expected.

Is there anything wrong with the way I declared the parameters?

You cannot "pattern match" a tuple in the parameter list of a method. Use def subtractOne(x: Occurrences, e: (Char,Int)): Occurrences then refer your tuple elements via e._1 and e._2 — metaphori
– metaphori, Commented Dec 12, 2015 at 15:35

vvg · Accepted Answer · 2015-12-12 15:32:34Z

2

Do not use brackets in parameter list. Unless you want to define tuple but it should be done with one name.

def subtractOne(x: Occurrences, char: Char, nr: Int): Occurrences = x match {

answered Dec 12, 2015 at 15:32

vvg

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freakybit · Accepted Answer · 2015-12-12 15:37:58Z

2

Tuples are defined under one name - charAndNr: (Char, Int) Also Nil is preferred to List()

answered Dec 12, 2015 at 15:37

freakybit

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