CODEWITHSUNDEEP
scala
shirin
shirin

Reputation: 192

Create A singletonSet Function Which Creates A Singleton Set From One Integer Value In SCALA

I've been asked to create a singletonSet function which creates a singleton set from one integer value: The code I used:

    def singletonSet(elem: Int): Set = {
    def isInSet (givenElement: Int) = 

          if (elem == givenElement) true
          else false

     isInSet
  }

checking online somebody did:

  def singletonSet(elem: Int): Set = {
    x => List(elem).contains(x)
  }

does that mean he/she put the element in a list and called the .contains() function on it? and I don't get what x does here? I tried this code. It runs with no error. I just don't get it. Thank you.

Upvotes: 1

Views: 1847

Answers (2)

Ivan
Ivan

Reputation: 462

As I understand

type Set = Int => Boolean

So x is just an Int that the returned function applies.

does that mean he/she put the element in a list and called the .contains() function on it?

Yes it looks so and we can simplify it:

  def singletonSet(elem: Int): Int => Boolean  = {
    x:Int => elem == x:Boolean
  }

Let's remove types 

  def singletonSet(elem: Int): Int => Boolean = {
    x => elem == x
  }

and replace x with placeholder _

def singletonSet(elem: Int) = elem == (_:Int)

Upvotes: 4

jmoyano
jmoyano

Reputation: 108

I imagine the Set you are defining here is not a scala.immutable.Set trait right? Regarding the code, calling List(something) basically calls the apply method on the List companion object to create an immutable List.

The function singletonSet basically returns a higher order function that takes an element named x and returns a boolean, but I don't think that piece of code compiles as it is missing type information on the x parameter.

Upvotes: 0

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