Scala: Operator Pattern Matching

Question

Is it possible in Scala to do pattern matching with an operator? I want to input a tuple, for example ("Hello World", +) or ("Good Afternoon", /) and do different actions for different operators, like:

mytuple match {
  case (SomeRegex(str), +) => println(str + " the same")
  case (SomeRegex(str), /) => println(str + " but different")
}

How can I correctly do this? I don't care what the operators do, I just want them as a kind of environment.

Maybe even passing the char +or / along is considered best practice, but I hardly believe it.

Levi Ramsey · Accepted Answer · 2017-12-21 17:16:42Z

1

Where would the + and * be coming from? And what would the type of mytuple be?

Depending on your answer to those, this might be a reasonable answer.

The language doesn't really expose * and + as objects (at least not in the way it seems like you're aiming for).

sealed trait Op
case object `+` extends Op
case object `*` extends Op
// ...

With those definitions in hand...

def dispatch(mytuple: (String, Op)): Unit =
  mytuple match {
    case (SomeRegex(str), `+`) => println(str + " the same")
    case (SomeRegex(str), `*`) => println(str + " but different")
    case _ => ()
  }

You can treat + and * (or any other string that the parser might have treated otherwise: def type class some identifier with spaces) as regular identifiers by wrapping them in `'s.

answered Dec 21, 2017 at 17:16

Levi Ramsey

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