johnynek

def orElse[A,B](fna: A => Option[B])(fni: B => Option[A])(implicit bi: Bijection[A,B]): Bijection[A,B] =
  new Bijection[A,B] {
    def apply(a: A) = fna(a).getOrElse(bij(a))
    override invert(b: B) = fni(b).getOrElse(bij.invert(b))
  }

johnynek

trait AwesomeFns {
  val myfun = { x: Int => 2*x }
}

object BaseFns extends AwesomeFns {
  val myfun2 = { x: Int => 4*x }
  def apply(x: Int) = myfun.apply(x)
}

// Trying to serialize myfun2 with Kryo fields serializer works, but not myfun.

johnynek

import org.scalacheck.Arbitrary
import org.scalacheck.Prop.forAll


object GraphTest extends Properties("GraphTest") {
  def find[K,V](walkfn: Set[K] => Map[K,Set[K]], endsOnly: Boolean)(
    s: Set[K], acc: Set[K] = Set[K](), visited: Set[K] = Set[K]()): Set[K] = {
    if(s.isEmpty) {
      acc
    }

johnynek

abstract class Marker(val g: AnyRef)
// Codegen 100 - 1000 of these, or use ASM to generate them on the fly
class Marker1(g: AnyRef) extends Marker(g)
class Marker2(g: AnyRef) extends Marker(g)

type Fn = (AnyRef) => Marker

class Markers(markers: List[(Fn, Class[_])], mmap: Map[Manifest[T], (Fn, Class[_])] = Map.empty) {
  def get[T](implicit mf: Manifest[T]): (Fn, Class[_], Markers) = {
    mmap.get(mf) { case (fn,cls) =>

johnynek

import annotation.implicitNotFound

@implicitNotFound(msg = "This message can never appear!")
trait ~>[A, B] { self =>
  def apply(a: A): B
  def invert(b: B): A = inverse.apply(b)
  def inverse: B ~> A = new ~>[B,A] {
    def apply(b: B) = self.invert(b)
    override def invert(a: A) = self(a)
  }

johnynek

package com.twitter.bijection

/** Deals with the type-system issue around resolving implicit bijections.
 * Bijection[A,B] or Bijection[B,A], which should
 * be equivalent. Only use this type as an implicit parameter.
 */
import scala.annotation.implicitNotFound
@implicitNotFound(msg = "Cannot find ImplicitBijection type class from ${A} to ${B}")
sealed trait ImplicitBijection[A, B] extends (A => B) with java.io.Serializable {
  def bijection: Bijection[A, B]

johnynek

#!/bin/sh
exec scala -savecompiled "$0" "$@"
!#
/**
 *  You should be able to run this file if you have scala installed:
 *  either make it executable, or run it with: "scala MapReduceToy.scala < someInputFile.txt"
 */

// Toy Map Reduce framework:
class MapReduce[T,K,V,R](flatMapFn: (T) => Iterable[(K,V)], reduceFn: ((K,Iterable[V])) => R) {

johnynek

#!/bin/sh
exec scala -savecompiled "$0" "$@"
!#

// Toy Map Reduce framework:
class MapReduce[T,K,V,R](flatMapFn: (T) => Iterable[(K,V)], reduceFn: ((K,Iterable[V])) => R) {

  def apply(input: Iterable[T]): Map[K,R] = {
    // Apply the flatMap function:
    val mapped: Iterable[(K,V)] = input.flatMap(flatMapFn)

johnynek

#!/bin/sh
exec scala -savecompiled "$0" "$@"
!#

// Toy Map Reduce framework:
class MapReduce[T,K,V,R](flatMapFn: (T) => Iterable[(K,V)], reduceFn: ((K,Iterable[V])) => R) {

  def apply(input: Iterable[T]): Map[K,R] = {
    // Apply the flatMap function:
    val mapped: Iterable[(K,V)] = input.flatMap(flatMapFn)

johnynek

#!/bin/sh
exec scala -savecompiled "$0" "$@"
!#

// Toy Map Reduce framework:
class MapReduce[T,K,V,R](flatMapFn: (T) => Iterable[(K,V)], reduceFn: ((K,Iterable[V])) => R) {

  def apply(input: Iterable[T]): Map[K,R] = {
    // Apply the flatMap function:
    val mapped: Iterable[(K,V)] = input.flatMap(flatMapFn)