channingwalton

object play {
  import scalaz._
  import Scalaz._

  def foo(i: Int) =  if (i > 0) Some(i) else None
 
  def boo(i: Int) =  if (i <= 0) Some(0) else None

  val l = foo _ :: boo _ :: Nil
 

channingwalton

object MonadWriterExample extends App {
  import scalaz._
  import Scalaz._

  implicit val monadWriter = EitherT.listenableMonadWriter[Writer, String, String]

  case class Person(firstName: String, age: Int, car: Option[String])

  def notEmpty(s: String) = Option(s).filter(x ⇒ !x.isEmpty && !x.forall(_.isWhitespace)) match {
    case Some(r) ⇒ monadWriter.right[String](r)

channingwalton

def setL[T, A, B](la: Lens[T, A], lb: Lens[T, B])(a:A, b: B)(t: T): T = la.set(lb.set(t, b), a)

def setL[T, A, B, C](la: Lens[T, A], lb: Lens[T, B], lc: Lens[T, C])(a:A, b: B, c: C)(t: T): T = lc.set(setL(la, lb)(a,b)(t), c)

def setL[T, A, B, C, D](la: Lens[T, A], lb: Lens[T, B], lc: Lens[T, C], ld: Lens[T, D])(a:A, b: B, c: C, d: D)(t: T): T = ld.set(setL(la, lb, lc)(a,b, c)(t), d)

channingwalton

trait FooComponent {

  def bar: BarComponent#Bar

  case class Foo(foofy: String)
}

trait BarComponent {
  def foo: FooComponent#Foo

channingwalton

package stereotypes

import shapeless._
import Searchable._

object FunctionThisUp {

  // pretend we have some case classes - they needn't be ours of course
  case class Name(name: String)
  case class Description(description: String)

channingwalton

// Inspired by http://dave.fayr.am/posts/2012-10-4-finding-fizzbuzz.html
object FizzBuzz extends App {
  import scalaz._
  import Scalaz._

  def fizzbuzz(i: Int) = ((i % 3 == 0) option "fizz") |+| ((i % 5 == 0) option "buzz") | i.shows 
  
  for (i <- 1 to 100) {println(i + " " + fizzbuzz(i))}
}

channingwalton

@channingwalton Recently read »I, Robot« from Asimov. The short stories are entertaining and very thoughtful.

@channingwalton I would like a wizard where I tell it I like Asimov (especially Daneel and Giskard) and Clarke, and it recommends others.

@channingwalton pretty much anything by Alastair Reynolds. House of Suns is particularly great.

@channingwalton I’ve enjoyed the Laundry novels by Charles Stross.

@channingwalton "Wool" series by Hugh Howey.

channingwalton

object KleisliValidation extends App {
  import scalaz._
  import Scalaz._
  import scala.util.control.Exception._

   implicit def vm = Validation.validationMonad[String]

  type EValidation[+T] = Validation[String, T]
  
  def toDouble(s: String): EValidation[Double] = allCatch.either(s.toDouble).fold(_.toString.fail, _.success)

channingwalton

object KleisliValidation extends App {
  import scalaz._
  import Scalaz._
  import scala.util.control.Exception._

  type EValidation[+T] = Validation[String, T]
  implicit val binding = new Bind[EValidation] {
    def map[A, B](fa: EValidation[A])(f: A => B): EValidation[B] = fa.map(f)
    def bind[A, B](fa: EValidation[A])(f: A => EValidation[B]): EValidation[B] = fa.flatMap(f)
  }

channingwalton

import scalaz._
import Scalaz._

/**
 * Use the state monad to 'process a trade' and store the new trade.
 * As well as processing the trade, handle validation errors.
 */
object StateMonad extends App {

  case class Trade(info: String)