fedesilva

module Main where

--------------------------------------------------------------------------------
-- | This is the `Maybe` data type:
-- |
-- | > data Maybe a
-- | > = Nothing
-- | > | Just a
-- |
-- | `Maybe` is a sum type that can be parameterized over a given `a` type, such

fedesilva

Easiest HDFS cluster in the world with kubernetes.

Inspiration from kimoonkim/kubernetes-HDFS

kubectl create -f namenode.yaml
kubectl create -f datanode.yaml

Setup a port-forward to so you can see it is alive:

fedesilva

This is a little trick I use to spin up the packages instalation on Debian/Ubuntu boxes in Vagrant.

I add a simple function that checks if a directory named something similar to ~/.vagrant.d/cache/apt/opscode-ubuntu-12.04/partial (it may have another path in Windows or MacOS) and create the directory if it doesn't already exist.

def local_cache(basebox_name)
  cache_dir = Vagrant::Environment.new.home_path.join('cache', 'apt', basebox_name)
  partial_dir = cache_dir.join('partial')
  partial_dir.mkdir unless partial_dir.exist?
 cache_dir

fedesilva

#!/bin/bash
# bash generate random alphanumeric string
#

# bash generate random 32 character alphanumeric string (upper and lowercase) and 
NEW_UUID=$(cat /dev/urandom | base64 | tr -dc 'a-zA-Z0-9' | fold -w 32 | head -n 1)

# bash generate random 32 character alphanumeric string (lowercase only)
cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 32 | head -n 1

fedesilva

[Unit]
Description=Play2 Server for <site>
After=network.target
 
[Service]
Type=simple
PIDFile=<path>/RUNNING_PID
 
ExecStartPre=/bin/sh -c 'cd <path> ;/bin/rm RUNNING_PID ; sbt clean compile stage'
ExecStart=<path>/target/start

fedesilva

case class IO[A](unsafePerformIO: () => A) {
  def map[B](ab: A => B): IO[B] = IO(() => ab(unsafePerformIO()))
  def flatMap[B](afb: A => IO[B]): IO[B] =IO(() => afb(unsafePerformIO()).unsafePerformIO())
  def tryIO(ta: Throwable => A): IO[A] = 
    IO(() => IO.tryIO(unsafePerformIO()).unsafePerformIO() match {
      case Left(t) => ta(t)
      case Right(a) => a
    })
}
object IO {

fedesilva

// Create a new MergeStrategy for aop.xml files
val aopMerge: MergeStrategy = new MergeStrategy {
  val name = "aopMerge"
  import scala.xml._
  import scala.xml.dtd._

  def apply(tempDir: File, path: String, files: Seq[File]): Either[String, Seq[(File, String)]] = {
    val dt = DocType("aspectj", PublicID("-//AspectJ//DTD//EN", "http://www.eclipse.org/aspectj/dtd/aspectj.dtd"), Nil)
    val file = MergeStrategy.createMergeTarget(tempDir, path)

fedesilva

package test.zipper

object TreeZipper extends App {

  println("hello")

  // exp 2 * 3 + 4 * 6

  val _2 = Node("2", Nil)
  val _3 = Node("3", Nil)

fedesilva

Collections Redesign Proposal

I'm going to start off by motivating what I'm doing here. And I want to be clear that I'm not "dissing" the existing collections implementation or anything as unproductively negative as that. It was a really good experiment, it was a huge step forward given what we knew back in 2.8, but now it's time to learn from that experiment and do better. This proposal uses what I believe are the lessons we can learn about what worked, what didn't work, and what is and isn't important about collections in Scala.

This is going to start out sounding really negative and pervasively dismissive, but bear with me! There's a point to all my ranting. I want to be really clear about my motivations for the proposal being the way that it is.

Problems

Generic Interfaces

fedesilva

object ToFromMap {
  implicit def materialize[T]: ToFromMap[T] = macro impl[T]
  def impl[T: c.WeakTypeTag](c: Context): c.Expr[ToFromMap[T]] = {
    import c.universe._
    val wt = weakTypeOf[T]
    // Gets the type parameters, eg Holder[T, J] => List(T, J)
    val baseTypes = wt.baseClasses.head.asType.typeParams.map{ _.asType.toType }

    // Gives a Map(T -> Int, J -> Double) if we are extracting Holder[Int, Double]
    val myTypes = baseTypes zip wt.typeArgs toMap;