Question

I can understand this:

scala> def f(i: Int) = "dude: " + i
f: (i: Int)java.lang.String

scala> f(3)
res30: java.lang.String = dude: 3

It defines a function f that takes an int and returns a string that is of the form dude: + the int that is passed in.

Now the same function can be specified like this:

val f: Int => String = x => "dude: " + x
scala> f(3)
res31: String = dude: 3

• Why do we need two =>
• What does String = x mean? I thought that when you want to define something in Scala you’d do x:String?

Answer 1

You should parse it as

val (f: Int => String) = (x => "dude: " + x)

So it specifies that f has type (Int => String) and is defined as an anonymous function which takes an Int parameter (x) and returns a String.