Scala inference on _

Question

I'm a newbie to scala(fxnl programming), though I put _ in context in a few places like the below

list.map(_ * 1)

I couldn't completely understand this statement

val story = (catch _) andThen (eat _)

though I can infer from the calling

story(new Cat, new Bird)

that underscore serves as placeholders to the the argument positions, I want to understand the concept behind it.

Go through this answer to get a decent idea on use of underscore: http://stackoverflow.com/questions/8000903/what-are-all-the-uses-of-an-underscore-in-scala — Johny T Koshy, Sep 18 '14 at 13:52
Thank you found this as while searching http://www.slideshare.net/normation/scala-dreaded — Somasundaram Sekar, Sep 18 '14 at 14:45

Andrzej Jozwik · Answer 1 · 2014-09-19T06:40:05.840

Statement

val story = (catch _) andThen (eat _)

is incorrect - because catch is keyword.

But this is correct:

scala> def caught(x:Int) = x + 8
caught: (x: Int)Int

scala> def eat(x:Int) = x + 3
eat: (x: Int)Int

scala> val story = (caught _) andThen (eat _) // story is function.
story: Int => Int = <function1>

scala> story(90) // You put 90 - parameter for caught (first _). It returns 90 + 8 and put it to eat (second _). eat function return 98 + 3
res0: Int = 101

Scala inference on _

1 Answers1