debasishg

-- Inspired by the writings of Edward Kmett, Edward Yang and Gabriel Gonzalez
-- concerning free monads and the codensity transformation.
--
-- http://comonad.com/reader/2011/free-monads-for-less/
-- http://blog.ezyang.com/2012/01/problem-set-the-codensity-transformation/
-- http://www.haskellforall.com/2012/06/you-could-have-invented-free-monads.html
--
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FlexibleInstances #-}

debasishg

svn co http://svn.apache.org/repos/asf/hadoop/common/trunk hadoop-trunk -r 1178440
cd hadoop-trunk/
mvn clean install package -Dtar -Pdist -DskipTests -P-cbuild
cd hadoop-mapreduce-project/
mvn clean install package -Dtar -Pdist -DskipTests -P-cbuild assembly:assembly
mkdir ~/HADOOP_MAPREDUCE
cp ./../../hadoop-trunk/hadoop-common-project/hadoop-common/target/hadoop-common-0.24.0-SNAPSHOT.tar.gz ~/HADOOP_MAPREDUCE/.
cp ./../../hadoop-trunk/hadoop-mapreduce-project/target/hadoop-mapreduce-0.24.0-SNAPSHOT-all.tar.gz ~/HADOOP_MAPREDUCE/.
cd ~/HADOOP_MAPREDUCE
tar xvfz hadoop-common-0.24.0-SNAPSHOT.tar.gz ; mv hadoop-common-0.24.0-SNAPSHOT common

debasishg

----------------------------------------------------------------
-- Free Monad example agaist RWH 15.8
--
-- Original code: http://ideone.com/F49k71

import Control.Applicative
import Control.Monad.Free
import System.IO (Handle, IOMode(..), stdout)
import qualified System.IO as IO
import System.IO.Unsafe

debasishg

/*
Based on the second part of the talk "Dead-Simple Dependency Injection in Scala" by @runarorama at NEScala 2012
http://marakana.com/s/dependency_injection_in_scala,1108/index.html
*/

sealed trait KVS[A]
case class Put[A](key: String, value: String, a: A) extends KVS[A]
case class Get[A](key: String, h: String => A) extends KVS[A]
case class Delete[A](key: String, a: A) extends KVS[A]

debasishg

// At the external API level, use TypeTag
def extract[T: TypeTag](jsv: JsValue): T =
    extractImpl[T](jsv, typeOf[T])

// But use Type for everything else
def extractImpl[T](jsv: JsValue, tpe: Type): T = {
  // no need for m
  val ex = jsv match {
    case JsNumber(n) => n
    case JsString(s) => s

debasishg

import scala.reflect.runtime.universe._
import scala.reflect.api.{TypeCreator, Universe}

object Test extends App {
  def foo[T: TypeTag] = TypeTag(typeTag[T].mirror, new TypeCreator {
    override def apply[U <: Universe with Singleton](m: scala.reflect.api.Mirror[U]): U # Type = {
      typeTag[T].in(m).tpe match {
        case TypeRef(_, _, argHead :: Nil) => argHead.asInstanceOf[U#Type]
      }
    }

debasishg

14:26 ~/Projects/210x (2.10.x)$ scala
Welcome to Scala version 2.10.1-20130204-105326-3d318be51f (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_37).
Type in expressions to have them evaluated.
Type :help for more information.

scala> case class Shop(store: String, item: String, cost: Int) { def this() = this(null, null, 0) }
defined class Shop

scala> val t = typeOf[Shop]
t: reflect.runtime.universe.Type = Shop

debasishg

import concurrent.{ExecutionContext, Future => SFuture, Promise}                 
import util.Try                                                                                                 
                                                                                                                
import _root_.scalaz.\/                                                                                         
import _root_.scalaz.concurrent.{Task => ZTask}                                                                 
                                                                                                                
                                                                                                                
object Task {                                                                                                   
                                                                                                                
  def fromScala[A]                    

debasishg

#WARNING: Use at your own risk. No warranties expressed or implied. YMMV. Drive responsibly. Eat healthy.

#First, `cd` into the parent dir for all of your `sbt`/`maven` projects (I assume you have one of those)
find "$(cd ..; pwd)" -type d -name "target" -exec sudo tmutil addexclusion -p {} +

debasishg

scalaVersion := "2.11.8"
scalaOrganization := "org.typelevel"

libraryDependencies ++= Seq(
  "org.typelevel" %% "cats" % "0.9.0",
  "org.atnos" %% "eff" % "4.0.0"
)

addCompilerPlugin("org.spire-math" %% "kind-projector" % "0.9.3")