Using pattern matching to return a function

Question

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.

Mik378 · Accepted Answer · 2013-05-12 10:54:28Z

1

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
}

edited May 12, 2013 at 10:54

answered May 12, 2013 at 10:37

Mik378

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2 Comments

More Than Five Over a year ago

thanks. What about the more complex scenarios? Is it possible to use pattern matching?

drexin Over a year ago

In this case pattern matching does not make sense, but if you match directly on integers, the compiler can create a switch/case statement.

JasonG · Accepted Answer · 2013-05-12 15:56:58Z

0

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   }

answered May 12, 2013 at 15:56

JasonG

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