kevinwright

As compiled by Kevin Wright a.k.a @thecoda

(executive producer of the movie, and I didn't even know it... clever huh?)

please, please, please - If you know of any slides/code/whatever not on here, then ping me on twitter or comment this Gist!

This gist will be updated as and when I find new information. So it's probably best not to fork it, or you'll miss the updates!

Monday June 16th

jonsterling

1. Install libffi with my modified homebrew formula: https://github.com/jonsterling/homebrew/blob/master/Library/Formula/libffi.rb
2. export PKG_CONFIG_PATH=/usr/local/Cellar/libffi/3.0.13/lib/pkgconfig
3. cabal install libffi
4. cabal install idris

pthariensflame

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.

etorreborre

class Outer {
  class Inner
  type Type
}
trait Trait
object Object extends Outer {
  val inner = new Inner
}
class OuterP[A] {
  class InnerP[B]

mpilquist

import scalaz._
import Scalaz._
import scalaz.iteratee._
import EnumeratorT._

def counter[A, F[+_]: Pointed] =
  IterateeT.fold[A, F, Int](0) { (acc: Int, a: A) => acc + 1 }

def count[A, F[+_]: Monad](e: EnumeratorT[A, F]) =
  (counter[A, F] &= e).run

jamie-allen

import akka.actor._
import akka.pattern.ask
import akka.util._
import akka.util.duration._
import scala.util.control.Exception._

/**
 * To test, execute this code and use this command in a shell: "telnet localhost 8080"
 * At the prompt, type in numbers and press enter, and they will be accumulated, returning
 * the total value each time.

sadache

Enumeratee.map[Array[Byte]]{ e =>
  val length = e.size
  val CRLF = "\r\n".getBytes("UTF-8")
  (length.toHexString.getBytes ++ CRLF ++ e ++ CRLF):Array[Byte] 
} ><>
Enumeratee.trailing(Seq((0.toHexString.getBytes) ++ (CRLF ++ CRLF)))

sadache

If your csv doesn't contain escaped newlines then it is pretty easy to do a progressive parsing without putting the whole file into memory. The iteratee library comes with a method search inside play.api.libs.iteratee.Parsing :

def search (needle: Array[Byte]): Enumeratee[Array[Byte], MatchInfo[Array[Byte]]]

which will partition your stream into Matched[Array[Byte]] and Unmatched[Array[Byte]]

Then you can combine a first iteratee that takes a header and another that will fold into the umatched results. This should look like the following code:

// break at each match and concat unmatches and drop the last received element (the match)

tonymorris

case class ReaderWriterStateT[R, W, S, F[_], A](
  run: (R, S) => F[(W, A, S)]
) {
  def map[B](f: A => B)(implicit F: Functor[F])
      : ReaderWriterStateT[R, W, S, F, B] =
    ReaderWriterStateT {
      case (r, s) => F.map(run(r, s)) {
        case (w, a, s) => (w, f(a), s)
      }
    }

raichoo

case class Config(host: String, port: Int) {
  def prettyPrint(prefix: String, msg: String): String =
    List(prefix, ": ", msg, " on ", host, ":", port.toString).mkString
}

/**
  * Passing a configuration with implicits is like
  * working in the state monad. You can "put" a
  * new configuration even though we don't want that
  * to happen in this particular example. We don't