Continuation Passing Style - example converted to scala from haskell; perhaps a more idiomatic scala than https://gist.github.com/Yaneeve/19a2615f3e4ab45c87920d7eaf616ef2

cps_no_curry.scala

// https://en.wikibooks.org/wiki/Haskell/Continuation_passing_style#Passing_continuations

def add(x: Int, y:Int): Int = x + y

def addCps[R](x: Int, y: Int): ((Int => R) => R) = {
  def lambda[K]: (Int => K) => K = {k: (Int => K) => k(add(x, y))}
  lambda
}

def square(x: Int): Int = x * x 

def squareCps[R](x: Int): ((Int => R) => R) = { 
  def lambda[K]: (Int => K) => K = { k: (Int => K) => k(square(x)) }
  lambda
}

def pythagoras(x: Int, y: Int): Int = add(square(x), square(y))

def pythagorasCps[R](x: Int, y: Int): ((Int => R) => R) = {
  def lambda[K]: (Int => K) => K = {k: (Int => K) =>
    val `x^2`: (Int => K) => K = squareCps[K](x)
    val `y^2`: (Int => K) => K = squareCps[K](y)

    `x^2`{xSquared =>
      `y^2`{ySquared =>
        addCps[K](xSquared, ySquared)(k)
      }
    }
  }
  lambda
}

val sCps: (Int => Unit) => Unit = squareCps[Unit](2)
sCps({a => println(a)})

val aCps: (Int => Unit) => Unit = addCps[Unit](1, 2)
aCps({a =>
  val b = a*13
  println(b)
})

val pCsp: (Int => Unit) => Unit = pythagorasCps[Unit](3, 4)
pCsp(println)

// https://scastie.scala-lang.org/Yaneeve/PIcmIoO6SJyJREjNezp8qg