Question

I realize the following function calls are all same, but I do not understand why.

val list = List(List(1), List(2, 3), List(4, 5, 6))

list.map(_.length)   // res0 = List(1,2,3) result of 1st call

list map(_.length)   // res1 = List(1,2,3) result of 2nd call

list map (_.length)  // res2 = List(1,2,3) result of 3rd call

I can understand 1st call, which is just a regular function call because map is a member function of class List

But I can not understand 2nd and 3rd call. For example, in the 3rd call, how can Scala compiler know “(_.length)” is parameter of “map”? How can compiler know “map” is a member function of “list”?

Answer 1

The only difference between variant 2 and 3 is the blank in front of the parenthesis? This can only be a delimiter – list a and lista is of course different, but a opening parens is a new token, and you can put a blank or two or three in front – or none. I don’t see how you can expect a difference here.

In Java, there is no difference between

 System.out.println ("foo"); 

// and

 System.out.println("foo"); 

too.