noelmarkham

scala> import scalaz._, Scalaz._
import scalaz._
import Scalaz._

scala> def str(x: Int): Option[String] = Some(x.toString)
str: (x: Int)Option[String]

scala> def toInt(x: String): Option[Int] = Some(x.toInt)
toInt: (x: String)Option[Int]

noelmarkham

scala> import scalaz._
import scalaz._

scala> import Scalaz._
import Scalaz._

scala> def check(i: Int, divisor: Int, s: String): Option[String] = if (i % divisor == 0) s.some else None
check: (i: Int, divisor: Int, s: String)Option[String]

scala> (1 to 50) map (i => (check(i, 3, "Fizz") |+| check(i, 5, "Buzz")).getOrElse(i))

noelmarkham

public class GenericVariance {

    class A {}
    class B extends A {}

    @Test
    public void checkTypes() {
        assertTrue(new B() instanceof A);

        final List<A> listOfA = new ArrayList<>();

noelmarkham

scala> :power
** Power User mode enabled - BEEP BOOP SPIZ **
** :phase has been set to 'typer'.          **
** scala.tools.nsc._ has been imported      **
** global._ and definitions._ also imported **
** Try  :help,  vals.<tab>,  power.<tab>    **

scala> :paste
// Entering paste mode (ctrl-D to finish)

noelmarkham

object RefactorPuzzle {
  case class IntRdr[+A](read: Int => A) {
    def map[B](f: A => B): IntRdr[B] =
      IntRdr(f compose read)

    def flatMap[B](f: A => IntRdr[B]): IntRdr[B] =
      IntRdr(n => f(read(n)).read(n))
  }

  object IntRdr {

noelmarkham

import scala.concurrent._
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration._

def fut(name: String, waitTime: Duration, result: Int): Future[Int] = {
  Future {
    println(s"$name started")
    Thread.sleep(waitTime.toMillis)
    println(s"$name finished")
    result

noelmarkham

import scalaz._
import syntax.std.option._
import OptionT._
import scala.concurrent._
import scala.concurrent.duration._

import scala.concurrent.ExecutionContext.Implicits.global

val o1 = 1.some
val o2 = 2.some

noelmarkham

import scalaz._
import Scalaz._
import \&/._

sealed trait Error
case class NotFatalError(reason: String) extends Error
case class FatalError(reason: String) extends Error

def function(i: Int): List[Error] \&/ Int = i match {

noelmarkham

scala> val FL = Functor[List]
FL: scalaz.Functor[List] = scalaz.std.ListInstances$$anon$1@575f20e3

scala> val FF = Functor[Future]
FF: scalaz.Functor[scala.concurrent.Future] = scalaz.std.FutureInstance@678bc1a9

scala> val FF_FL = FF compose FL
FF_FL: scalaz.Functor[[α]scala.concurrent.Future[List[α]]] = scalaz.Functor$$anon$1@49487384

scala> val values = Future(List(1, 2, 3, 4, 5))

noelmarkham

scala> usernameToUserIdLens.get("Alan").foreach(println)
** SELECT ID FROM USERS WHERE NAME = Alan
1

scala> userIdToStreetNameLens.get(1).foreach(println)
** SELECT STREET_NAME FROM ADDRESS WHERE USER_ID = 1
High Street

scala> val usernameToStreetNameLens = usernameToUserIdLens >=> userIdToStreetNameLens