CODEWITHSUNDEEP
scalapattern-matchingmatch
Derp
Derp

Reputation: 143

Pattern matching checking for type of tuple

I am trying to use Scala's pattern matching feature to check for the type of the first parameter, and to accept any arbitrary type for the second parameter- though I'm not sure syntactically how this works in Scala as I am fairly new, and I cannot find anything as to how tuples work with one another in Scala as it relates to pattern matching and case statements.

My initial attempt:

case foo => (eval(e1, e2), eval(e1, e2)) match
{
    case (S(e1), _) => (bar(e1, e2) + bar(e1, e2))
    case _ => ???
}

Wherein, this should, in this case, check that the first argument is a string, and accept the second to be whatever, and then do whatever bar wants.

Further, I have seen examples like so:

case (_: String, _: Int) => ???

however, I am unclear as to how you reference these parameters in your right hand statement.

What is the proper method of referencing these _ parameters in a statement?

Upvotes: 1

Views: 769

Answers (1)

Nagarjuna Pamu
Nagarjuna Pamu

Reputation: 14825

You use : to enfore the type. Below the example. You can refer to any value using a variable and without explicitly declaring type.

Scala REPL

scala> :paste
// Entering paste mode (ctrl-D to finish)

("Java", 1) match {
  case (str: String, v) => println(s"value: $v")
  case _ => println("something")
}

// Exiting paste mode, now interpreting.

value: 1

Upvotes: 1

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