johnynek

use std::old_io as io;
use std::sync::mpsc::channel;
use std::thread::Thread;
use std::ops::Fn;
use std::marker::PhantomData;

pub struct Test<F, X>(F, PhantomData<X>);

impl <F, X> Test<F, X> where F: Fn(X) {
  fn go(self, x: X) {

johnynek

object exp {


case class Scope(m: Map[Var[_], Exp[_]]) {
  def put[T](pair: (Var[T], Exp[T])): Scope = new Scope(m + pair)
  def apply[T](v: Var[T]): Either[String, Exp[T]] = m.get(v) match {
    case Some(exp) => Right(exp.asInstanceOf[Exp[T]])
    case None => Left(s"$v not found. Scope: $m")
  }
}

johnynek

Better Dependency Hygiene With Private Dependencies On JVM

A common pain when working with large projects is the diamond dependency. Consider a commonly used library such as ASM. One wants to build a big application reusing many powerful libraries, but unfortunately many of my desired dependencies themselves depend on different and incompatible versions of ASM. While compiling my code, since ASM does not appear in any APIs I touch, everything compiles fine, but at runtime the JVM only includes one version of classes of a given name leading to runtime binary errors.

OSGI Bundles are related to solving this problem, but it appears that is a heavy solution that has proven to be too cumbersome to actually use. Here we propose a lighter weight approach that benefits each incremental project that adopts this method.

Private dependencies are implemented by a build tool plug-in. In the build where one declares dependencies, one can label a jar dependency to be a private dependency. A private dependency means tha

johnynek

-- If the length is < n+1, it is less than n+2
weakenPair: (p: Fin n ** Vect (finToNat p) a) -> (p1: Fin (S n) ** Vect (finToNat p1) a)
weakenPair (FZ ** v) = (FZ ** v)
weakenPair (FS k ** v) = believe_me (FS k ** v) -- How to prove this branch?

filt : Vect n a -> (fn: a -> Bool) -> (p: Fin (S n) ** Vect (finToNat p) a)
filt [] _ = (0 ** [])
filt (x :: xs) fn with (filt xs fn)
  | (p' ** xs') = if (fn x) then ((shift 1 p') ** (x :: xs')) else weakenPair (p' ** xs')

johnynek

package com.twitter.scalding

class WordCount(args : Args) extends Job(args) {
  TextLine( args("input") ).read.
    flatMap('line -> 'word) { line : String => line.split("\\s+") }.
    groupBy('word) { _.size }.
    write( Tsv( args("output") ) )
}

johnynek

#!/usr/bin/env python

#closures are a poor man's object (and vice-versa)
# http://okmij.org/ftp/Scheme/oop-in-fp.txt

class StoresStuff:
  def __init__(self, member):
    self.member = member

def poorMansObject(init_member):

johnynek

|\intersection_{i=(1..k)} s_i| = -\sum_{b=(0..2^k - 1)} (-1)^{|b|} |\union_i (s_i)^(b_i)|

where s_i^1 = s_i, and s_i^0 = {} (the empty set).
|b| is the number of 1 values in the binary representation.

Proof, base case = k = 2 (which is to say there is just s_1, s_2).
|s_1 n s_2| = -|{}| + |s_1| + |s_2| - |s_1 u s_2|
which is clearly true because |{}| = 0, and the fact that
|s_1| + |s_2| = |s_1 n s_2| + |s_1 u s_2|

johnynek

package com.twitter.scalding

import cascading.tuple.Fields
import cascading.tuple.{Tuple => CTuple, TupleEntry}

class MemoryGroupBuilder(val input : List[TupleEntry],
  val prevOutput : TupleEntry = new TupleEntry(),
  override val sorting : Option[Fields] = None)

  extends ReduceOperations[MemoryGroupBuilder] {

johnynek

(def bignumber "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450")

(def

johnynek

ackage com.twitter.ads.batch.experimental.oscar

import com.twitter.scalding._
import com.twitter.pluck.job._
import com.twitter.pluck.source._
import com.twitter.pluck.source.matrix._
import com.twitter.pluck.mathematics._
import com.twitter.scalding.mathematics.Monoid

/*