Single Argument to one-line Function Literals

[archsky]

From the Programming in Scala eBook page 78

args.foreach(arg => println(arg))

If a function literal consists of one statement that takes a single argument, you need not explicitly name and specify the argument. Thus, the following code also works:

args.foreach(println)

Good. Now on page 88, thrill is a list, scala REPL says: thrill: List[String] = List(WILL, FILL, UNTIL)

thrill.count(s => s.length == 4)

Now, here, inside the parentheses, it is a function literal, and to me it seems that it contains a single statement, i.e., (according to my current understanding of single statement) something in one line (and that without semi-colons) and the argument for this function literal is also one, i.e., 's'

I tried to apply the former approach, to eliminate the 's' in the latter example.

scala> thrill.count(length == 4)

With the response

<console>:12: error: not found: value length
       thrill.count(length == 4)
                    ^

What is amiss here?

[Dennis Haupt]

thrill.count(length == 4)

-> compiler does not know what to call "length" on. it checks if there is a def or val called length with zero parameters and does not find any

 

thrill.count(_.length == 4)

-> _ represents the function argument

 

 

 

 

Gesendet: Mittwoch, 07. Oktober 2015 um 16:42 Uhr
Von: archsky <luna...@gmail.com>
An: scala-user <scala...@googlegroups.com>
Betreff: [scala-user] Single Argument to one-line Function Literals

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[Dennis Haupt]

thrill.count(length == 4)

-> compiler does not know what to call "length" on. it checks if there is a def or val called length with zero parameters and does not find any

 

thrill.count(_.length == 4)

-> _ represents the function argument

Gesendet: Mittwoch, 07. Oktober 2015 um 16:42 Uhr
Von: archsky <luna...@gmail.com>
An: scala-user <scala...@googlegroups.com>
Betreff: [scala-user] Single Argument to one-line Function Literals

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