CODEWITHSUNDEEP
scalainput
Kurtis Nusbaum
Kurtis Nusbaum

Reputation: 30825

Reading input throws compile error

Pretty new to scala. I have this function:

  def retrieveValue(valueName:String) : Double = {
    for (ln <- io.Source.stdin.getLines) {
      val parseResult = parseValue(ln)
      parseResult match {
        case Right(x) => return x
        case Left(error) => println(error.message + " Please try again.")
      }
    }
  }

And I'm getting this compile error:

QuadSolver.scala:14: error: type mismatch;
found   : Unit
required: Double
for (ln <- io.Source.stdin.getLines) {

What exactly am I doing wrong?

Upvotes: 1

Views: 46

Answers (1)

Mik378
Mik378

Reputation: 22171

parseResult match {
    case Right(x) => x  //note that `return` keyword is not needed
    case Left(error) => println(error.message + " Please try again.") //returns Unit
}

This piece of code return either a Double or a Unit (Unit provided by println), therefore compiler expecting a Double as method's return type obviously complains.

In functional programming, it's better to have each function strictly following Single-Responsibility Principle.
Thus, you should have one function aiming to retrieve the value and one to print the result.

Upvotes: 1

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