tomwadeson

module HarryPotter where

import qualified Data.Map.Strict as Map
import Data.Maybe (catMaybes) 

type Copies = Int
type Discount = Double
type Price = Double
type DiscountScheme = Int -> Discount

tomwadeson

scala> case class Callback[A](f: (A => Unit) => Unit) {
     |   def map[B](g: A => B): Callback[B] = Callback { (h: B => Unit) => f(a => h(g(a)))  }
     |   def flatMap[B](g: A => Callback[B]): Callback[B] = Callback { (h: B => Unit) => f(a => g(a).f(b => h(b))) }
     | }
defined class Callback