Uses for Scala continuations

Question

How are people using continuations on a larger and smaller scale in Scala?

Are any parts of the Scala standard library written in CPS?

Are there any major performance penalties in using continuations?

Answer 1

I'm using this to turn asynchronous functions of the form def func(...)(followup: Result => Unit): Unit so that instead of writing

foo(args){result1 => 
  bar(result1){result2 => 
     car(result2) {result3 =>
       //etc.
     }
  }
}

you can write

val result1 = foo(args)
val result2 = bar(result1)
val result3 = car(result2)

or

car(bar(foo(args)))

(note: the functions are not limited to one argument or just the use of previous results as arguments)

See http://www.tikalk.com/java/blog/asynchronous-functions-actors-and-cps