Different Syntax for functions in Scala

Question

I have the following two methods in Scala:

def myFunc: Int => String = { age =>
  "Here " + age
}

def myFunc2 (age: Int) : String = {
  "Here" + age
}

Is there any difference in these two methods? (other than the names of course). The syntax looks quite different to me. Is it just a matter of style? Is one prefered over the other?

You don't have functions here. These are methods. One of them evaluates to a function, and you could convert these to functions, but the code you've posted only defines methods. — user2357112
– user2357112, Commented Jul 10, 2016 at 3:32
Ok - good point. I have corrected the terminology. Is there any difference in the two methods though? — Hutch
– Hutch, Commented Jul 10, 2016 at 3:43

Yuval Itzchakov · Accepted Answer · 2016-07-10 06:33:59Z

3

Yes, there is a difference. The former is a method which takes no arguments and returns a function of type Function1[Int, String]. The latter is a method taking a String and returning an Int.

In Scala, methods with arity-0 can be declared and invoked without parenthesis, so invoking myFunction(1) and myFunction2(1) looks the same.

If we'd convert both methods to functions, you'd see the difference in the fact that the former would take the shape of Function0[Function1[Int, String]], while the latter would be Function1[Int, String]:

myFunc: Int => String
myFunc2: (age: Int)String

scala> myFunc _
res6: () => Int => String = <function0>

scala> myFunc2 _
res7: Int => String = <function1>

edited Jul 10, 2016 at 6:33

answered Jul 10, 2016 at 4:56

Yuval Itzchakov

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2 Comments

user2357112 Over a year ago

I think you might have the terms "former" and "latter" mixed up.

Yuval Itzchakov Over a year ago

@user2357112 Yup, you're right. Fixed that up, thanks!

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