CODEWITHSUNDEEP
scalapattern-matching
More Than Five
More Than Five

Reputation: 10419

Using pattern matching to return a function

I am trying to write a function that returns a function based on the input parameter.

def myFunction(x: Int): x => Boolean {
  x => if (x < 7) false
       if (x % 2 == 0) false
       else true
}

So if x is less than 7 or even false will be returned. Otherwise true is.

How do I write this using pattern matching?

And if it pointless to use pattern matching for Ints, what about something more complex like a list of Ints.

def myFunction(myList: List[Int]): x => Boolean {
  // just doing something simple here real life is more complex.
  x => if (myList.size() < 7) false
       else true
}

Thanks.

Upvotes: 1

Views: 129

Answers (2)

JasonG
JasonG

Reputation: 5962

I usually pattern match like this. Any expression returns a value - if else and matching should have approximately the same result.

  x match{
    case x if x < 7 => false
    case x if (x % 2 == 0) => false
    case _ => true   }

Upvotes: 0

Mik378
Mik378

Reputation: 22171

Pattern matching is useless when dealing with primitive objects.

Other alternative would be :

Option(3).map(x => x < 7 || x % 2 == 0).getOrElse(false)

But for this simple case, I prefer simple if/else.

For your second case, a function returning a partial function based on a List[Int] would be:

def myFunction(myList: List[Int]): List[Int] => Boolean = {
    case _ :: Nil  if (myList.size < 7) => false
    case _ => true
}

Upvotes: 1

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