andrejbauer

A bijection between numbers and pairs of numbers

Every once in a while I am faced with someone who denies that the rational numbers (or fractions, or pairs of integers) can be put into a bijective correspondence with natural numbers. To deal with the situation, I coded up the bijection. So now I can just say: "Really? Interesting. Please provide a pair of numbers (i,j) which is not enumerated by f, as defined in my gist." I am still waiting for a valid counter-example.

Anyhow, here is a demo of f and g at work. I am using the Python version, but a Haskell variant is included as well.

The 100-th pair is:

>>> f(100)

(10, 4)

sigrlami

WARNING This list outdated, for the up to date version visit https://haskellcosm.com

List of companies that use Haskell in Production

Types of work:

• RD - research&development
• PR - product
• IP - in-house product
• CO - consulting

milessabin

scala> trait Assoc[K] { type V ; val value: V }
defined trait Assoc

scala> def mkAssoc[V0](k: String, v: V0): Assoc[k.type] { type V = V0 } =
     |   new Assoc[k.type] { type V = V0 ; val value = v }
mkAssoc: [V0](k: String, v: V0)Assoc[k.type]{type V = V0}

scala> implicit def nameAssoc = mkAssoc("Name", "Mary")
nameAssoc: Assoc[String("Name")]{type V = String}

paulp

[?] (letrec length = (\l ⇒ ((cond (isNull l)) 0) (succ (length (tail l)))) in length)
| [+] t0
| [?] (\l ⇒ ((cond (isNull l)) 0) (succ (length (tail l))))
| | [+] t1
| | [?] (((cond (isNull l)) 0) (succ (length (tail l))))
| | | [+] t2
| | | [?] ((cond (isNull l)) 0)
| | | | [+] t3
| | | | [?] (cond (isNull l))
| | | | | [+] t4

ftrain

;; This is at: https://gist.github.com/8655399

;; So we want a rhyming dictionary in Clojure. Jack Rusher put up
;; this code here:
;; 
;; https://gist.github.com/jackrusher/8640437
;;
;; I'm going to study this code and learn as I go.
;;
;; First I put it in a namespace.

karlgluck

What's this all about?

Digital cryptography! This is a subject I've been interested in since taking a class with Prof. Fred Schneider back in college. Articles pop up on Hacker News fairly often that pique my interest and this technique is the result of one of them.

Specifically, this is about Lamport signatures. There are many signature algorithms (ECDSA and RSA are the most commonly used) but Lamport signatures are unique because they are formed using a hash function. Many cryptographers believe that this makes them resistant to attacks made possible by quantum computers.

How does a Lamport Signature work?

petehunt

macro := {
  rule infix { $obj $([ $key ] ...) | $rval:expr } => {
    $obj = mori.assoc_in($obj, [$key (,) ...].reverse(), $rval)
  }
}

macro hash_map {
  rule {{ $($key : $value) (,) ... }} => {
    mori.hash_map($($key, $value) (,) ...)
  }

markhibberd

package argonaut.example

import argonaut._, Argonaut._
import scalaz._, Scalaz._

object UnionExample extends {

  sealed trait Thing
  final case class One(n: String, i: Int) extends Thing
  final case class Two(n: String) extends Thing

debasishg

General Background and Overview

1. Probabilistic Data Structures for Web Analytics and Data Mining : A great overview of the space of probabilistic data structures and how they are used in approximation algorithm implementation.
2. Models and Issues in Data Stream Systems
3. Philippe Flajolet’s contribution to streaming algorithms : A presentation by Jérémie Lumbroso that visits some of the hostorical perspectives and how it all began with Flajolet
4. Approximate Frequency Counts over Data Streams by Gurmeet Singh Manku & Rajeev Motwani : One of the early papers on the subject.
5. [Methods for Finding Frequent Items in Data Streams](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.187.9800&rep=rep1&t

swannodette

(ns logic-ast.core
  (:refer-clojure :exclude [==])
  (:require [clojure.java.io :as io]
            [clojure.pprint :as pp]
            [cljs.env :as env]
            [cljs.analyzer.utils :as u]
            [cljs.analyzer :as ana]
            [clojure.core.logic
             :refer [run run* conde == fresh lcons partial-map defne] :as l]
            [clojure.core.logic.pldb :as pldb]))