Scala method created using function literals

Question

I am new to scala and was playing around with few concepts but got stuck with following one.

If i create a method like

def sample(value:Int) = {(x:Int)=>x+1}

This works in Scala and can be tested as sample(100), but I am not able to understand as how a method and literal here can be clubbed. Can someone explain what exactly is happening?

sample is a function which returns an anonymous function. All the concepts you're playing around, you just need to read them up a bit: docs.scala-lang.org/tutorials/tour/… and docs.scala-lang.org/tutorials/tour/higher-order-functions — The_Tourist
– The_Tourist, Commented Dec 6, 2016 at 20:52

Andrew · Accepted Answer · 2016-12-06 21:01:18Z

The parameter value here is never used and is therefore redundant. The method sample() returns a function which takes one integer parameter (which is discarded) and then adds 1 to it. So you get:

scala> def sample(value:Int) = { (x:Int) => x + 1 } sample: (value: Int)Int => Int scala> sample(100) res2: Int => Int = <function1> scala> sample(100)(10) res3: Int = 11 scala> val f = sample(99) f: Int => Int = <function1> scala> f(1) res4: Int = 2

You could use the value parameter in the following way:

scala> def plusX(value:Int) = { (x:Int) => x + value} plusX: (value: Int)Int => Int scala> val plus10 = plusX(10) plus10: Int => Int = <function1> scala> plus10(15) res7: Int = 25

Now plusX creates a function which takes a integer and adds the value value to it

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