Krasnyanskiy

# Set variables in .bashrc file

# don't forget to change your path correctly!

export GOPATH=$HOME/golang
export GOROOT=/usr/local/opt/go/libexec
export PATH=$PATH:$GOPATH/bin
export PATH=$PATH:$GOROOT/bin

Krasnyanskiy

function whatDoesItDo(val){

    return val ? 1 : 2;

}

Krasnyanskiy

ּ_בּ
בּ_בּ
טּ_טּ
כּ‗כּ
לּ_לּ
מּ_מּ
סּ_סּ
תּ_תּ
٩(×̯×)۶
٩(̾●̮̮̃̾•̃̾)۶

Krasnyanskiy

# Default system properties included when running spark-submit.
# This is useful for setting default environmental settings.

# Example:
# spark.master                     spark://master:7077
spark.eventLog.enabled           true
spark.eventLog.dir               file:///home/ozawa/sparkeventlogs
# spark.serializer                 org.apache.spark.serializer.KryoSerializer
# spark.driver.memory              5g
# spark.executor.extraJavaOptions  -XX:+PrintGCDetails -Dkey=value -Dnumbers="one two three"

Krasnyanskiy

package spire.algebra

import spire.syntax.eq._

trait MeetSemilattice[A] { self =>
  def meet(x: A, y: A): A

  def partialOrder: PartialOrder[A]

  def meetAlgebra: CSemigroup[A] =

Krasnyanskiy

Explaining Miles's Magic

Miles Sabin recently opened a pull request fixing the infamous SI-2712. First off, this is remarkable and, if merged, will make everyone's life enormously easier. This is a bug that a lot of people hit often without even realizing it, and they just assume that either they did something wrong or the compiler is broken in some weird way. It is especially common for users of scalaz or cats.

But that's not what I wanted to write about. What I want to write about is the exact semantics of Miles's fix, because it does impose some very specific assumptions about the way that type constructors work, and understanding those assumptions is the key to getting the most of it his fix.

For starters, here is the sort of thing that SI-2712 affects:

def foo[F[_], A](fa: F[A]): String = fa.toString

Krasnyanskiy

The Indexed Continuation Monad in Haskell, Scala, and C#

The indexed state monad is not the only indexed monad out there; it's not even the only useful one. In this tutorial, we will explore another indexed monad, this time one that encapsulates the full power of delimited continuations: the indexed continuation monad.

Motivation

The relationship between the indexed and regular state monads holds true as well for the indexed and regular continuation monads, but while the indexed state monad allows us to keep a state while changing its type in a type-safe way, the indexed continuation monad allows us to manipulate delimited continuations while the return type of the continuation block changes arbitrarily. This, unlike the regular continuation monad, allows us the full power of delimited continuations in a dynamic language like Scheme while still remaining completely statically typed.

Krasnyanskiy

The Indexed State Monad in Haskell, Scala, and C#

Have you ever had to write code that made a complex series of succesive modifications to a single piece of mutable state? (Almost certainly yes.)

Did you ever wish you could make the compiler tell you if a particular operation on the state was illegal at a given point in the modifications? (If you're a fan of static typing, probably yes.)

If that's the case, the indexed state monad can help!

Motivation

Krasnyanskiy

import scalaz._
import scalaz.std.list._
import scalaz.syntax.monad._
import scalaz.syntax.monoid._
import scalaz.syntax.traverse.{ToFunctorOps => _, _}

class Foo[F[+_] : Monad, A, B](val execute: Foo.Request[A] => F[B], val joins: Foo.Request[A] => B => List[Foo.Request[A]])(implicit J: Foo.Join[A, B]) {

def bar: Foo[({type l[+a]=WriterT[F, Log[A, B], a]})#l, A, B] = {
    type TraceW[FF[+_], +AA] = WriterT[FF, Log[A, B], AA]

Krasnyanskiy

trait %>[From, To] {
  def apply(x: From): To
}

def view[From, To](f: From => To): From %> To = 
  new %>[From, To] { 
    def apply(x: From): To = f(x) 
  }

implicit i: Int %> String = view(_.toString)