gfixler

Standardized Ladder of Functional Programming
http://lambdaconf.us/downloads/documents/lambdaconf_slfp.pdf

Level Key
0: I've never heard of this
1: I've heard of this
2: I've looked into this, but don't get it yet
3. I have a basic understanding/am using this
4. I've used this for a while/feel pretty solid on
5. I could comfortably teach this to others

runarorama

import scalaz._, Scalaz._

// Adjunction between `F` and `G` means there is an
// isomorphism between `A => G[B]` and `F[A] => B`.
trait Adjunction[F[_],G[_]] {
  def leftAdjunct[A, B](a: A)(f: F[A] => B): G[B]
  def rightAdjunct[A, B](a: F[A])(f: A => G[B]): B
}

// Adjunction between free and forgetful functor.

iravid

package freestate

sealed abstract class FreeState[S, A] { self =>
  def tag: Int

  final def map[B](f: A => B): FreeState[S, B] = self match {
    case FreeState.Pure(a) => FreeState.Pure(f(a))
    case _ =>
      FreeState.FlatMap(self, (a: A) => FreeState.Pure(f(a)))
  }