folone

import scalaz._, Scalaz._

case class Happy[A](a: A)
case class NewYear(year: Int)

implicit val happyInstance = new Applicative[Happy] {
  def point[A](a: ⇒ A) = Happy(a)
  def ap[A, B](fa: ⇒ Happy[A])(f: ⇒ Happy[A => B]) =
    f match {
      case Happy(f) ⇒ fa match {

folone

import Control.Applicative

data NewYear = NewYear Int
               deriving (Eq, Show)
data Happy a = Happy a
               deriving (Eq, Show)

instance Functor Happy where
  fmap f (Happy a) = Happy $ f a

folone

case class Reader[T, +A](run: T ⇒ A) {
  def map[B](f: A ⇒ B): Reader[T, B] =
    Reader((r: T) ⇒ f(run(r)))

  def flatMap[B](f: A ⇒ Reader[T, B]): Reader[T, B] =
    Reader((r: T) ⇒ f(run(r)).run(r))

  def &&&[B](x: Reader[T, B]): Reader[T, (A, B)] =
    for {
      a ← this

folone

import scalaz._, Scalaz._

case class Writer[W: Monoid, +A](run: (A, W)) {
  def map[B](f: A ⇒ B): Writer[W, B] =
    Writer {
      val (a, w) = run
      (f(a), w)
    }

  def flatMap[B](f: A ⇒ Writer[W, B]): Writer[W, B] =

folone

case class State[S, +A](run: S ⇒ (A, S))  {
  def map[B](f: A => B): State[S, B] =
    State(s ⇒ {
      val (a, t) = run(s)
      (f(a), t)
    })

  def flatMap[B](f: A ⇒ State[S, B]): State[S, B] =
    State(s ⇒ {
      val (a, t) = run(s)

folone

case class T() // your data type that you want to "implicitly" thread through

case class TReader[+A](run: T ⇒ A) {
  def map[B](f: A ⇒ B): TReader[B] =
    TReader((r: T) ⇒ f(run(r)))

  def flatMap[B](f: A ⇒ TReader[B]): TReader[B] =
    TReader((r: T) ⇒ f(run(r)).run(r))

  def &&&[B](x: TReader[B]): TReader[(A, B)] =

folone

class Monad m => Ref r m where
  ref :: a -> m (r a)
  (*) :: r a -> m a
  (*=) :: r a -> a -> m ()
  (*$) :: r a -> (a -> a) -> m ()
  r *$ f = (r *) >>= (*=) r . f

instance Ref IORef IO where
  ref = newIORef
  (*) = readIORef

folone

\documentclass{tufte-handout}

%\geometry{showframe}% for debugging purposes -- displays the margins

\usepackage{amsmath}

% Set up the images/graphics package
\usepackage{graphicx}
\setkeys{Gin}{width=\linewidth,totalheight=\textheight,keepaspectratio}
\graphicspath{{graphics/}}

folone

$ ghci
GHCi, version 7.4.2: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude> :l hello-ski.hs 
[1 of 1] Compiling Main             ( hello-ski.hs, interpreted )
Ok, modules loaded: Main.
*Main> main
Hello world!

folone

> console
[info] Starting scala interpreter...
[info] 
Welcome to Scala version 2.9.2 (OpenJDK 64-Bit Server VM, Java 1.6.0_24).
Type in expressions to have them evaluated.
Type :help for more information.

scala> import scala.xml._
import scala.xml._