Novice here. I came across this following piece of code
class A
class B extends A
val printB: B => Unit = { b => println("Blah blah") }
Can someone explain the printB function? I cannot understand what is b, since it isn't defined anywhere.
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espeirasbora
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http://docs.scala-lang.org/tutorials/tour/anonymous-function-syntax.html – Rich Henry Sep 16 '15 at 18:10
1 Answers
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printB is an anonymous function. It acts like this method:
def printBmethod(b: B): Unit = { println("Blah blah") }
Except that to make it a function, you have to eta-expand it like:
val printB = printBmethod _
See also: Difference between method and function in Scala
Explaining the lambda itself, b is an input parameter, so you can call it like:
printB(new B)
B => Unit means a function which takes B and returns Unit so scala is looking for something that takes B and returns Unit - like b: B => ...
P.S. The raw code without type inference for b looks like:
val printB: B => Unit = { b: B => println("Blah blah") }
So here you see what actually b is.
