ejackson

(ns timetable.core
  (:refer-clojure :exclude [==])
  (:use [clojure.core.logic]
        [clojure.tools.macro]))

;; Basic form. Works
(run 10 [q]
     (== [(lvar) (lvar) (lvar)] q)
     (membero :history q)
     (membero :math q)

ejackson

(ns timetable.core2
  (:refer-clojure :exclude [==])
  (:use [clojure.core.logic]
        [clojure.tools.macro]))

;;  --------------------------------------------------------
;;   Useful goals
(defne rembero 
  "Succeeds if out is the list l with the first instance of element x removed"
  [x l out]

ejackson

;;; zoo.clj -- Statistics library for Clojure built on the CERN Colt Library

;; by David Edgar Liebke http://incanter.org
;; March 11, 2009

;; Copyright (c) David Edgar Liebke, 2009. All rights reserved.  The use
;; and distribution terms for this software are covered by the Eclipse
;; Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
;; which can be found in the file epl-v10.htincanter.at the root of this
;; distribution.  By using this software in any fashion, you are

ejackson

(ns datomic-play.core
  (:use [datomic.api :only [db q] :as d])
  (:require [clojure.core.logic :as l]
            [clojure.pprint :as pp]))

(def uri "datomic:dev://localhost:4334/hello")

(defprotocol IUnifyWithDatum
  (unify-with-datum [u v s]))

ejackson

;;     MM""""""""`M
;;     MM  mmmmmmmM
;;     M`      MMMM 88d8b.d8b. .d8888b. .d8888b. .d8888b.
;;     MM  MMMMMMMM 88''88'`88 88'  `88 88'  `"" Y8ooooo.
;;     MM  MMMMMMMM 88  88  88 88.  .88 88.  ...       88
;;     MM        .M dP  dP  dP `88888P8 '88888P' '88888P'
;;     MMMMMMMMMMMM
;;
;;         M""MMMMMMMM M""M M""MMMMM""M MM""""""""`M
;;         M  MMMMMMMM M  M M  MMMMM  M MM  mmmmmmmM

ejackson

  2723920    2012-05-18 08:13:02  public     unify_datums.clj
  f262c68... 2012-04-19 12:45:56  private    
  1762346    2012-02-07 21:57:11  public     Zoo Proposal
  1726444    2012-02-02 23:31:59  public     Attempt at the problem
+ 1674762    2012-01-25 04:39:48  public     Unusual behaviour of symbol-macrolet
  1431199    2011-12-04 20:33:49  public     
  1423801    2011-12-02 16:16:59  public     A quick moving average
  1380546    2011-11-20 17:37:54  public     
  1319377    2011-10-27 12:05:36  public     
  1293529    2011-10-17 19:29:20  public     

ejackson

(def v (into [] (repeatedly 1e5 #(rand 100))))

(defn rnd [x]
  (Math/round x))

(defn prnd ^long [^double x]
  (Math/round x))

(time (r/fold + (r/map rnd v)))
(time (r/fold + (r/map prnd v)))

ejackson

-----------= Tales of Yore =-----------
* Hackers: Heroes of the Computer Revolution
 (http://www.amazon.co.uk/Hackers-Heroes-Computer-Revolution-Anniversary/dp/1449388396)

* The soul of a new machine 
(http://www.amazon.co.uk/Soul-New-Machine-Tracy-Kidder/dp/0140062491/ref=sr_1_2?s=books&ie=UTF8&qid=1363772696&sr=1-2)

* The brainmakers
(http://www.amazon.co.uk/Brainmakers-Scientists-Moving-Beyond-Computers/dp/067151055X/ref=sr_1_1?s=books&ie=UTF8&qid=1363772724&sr=1-1)

ejackson

<h1>Introduction</h1>
This is a brief post about how laziness can be used to construct a step-wise quicksort, or somebody gets excited about laziness.
<P>
Laziness is not something I'd come across before Clojure, and I've been repeatedly bitten by forgetting about it.  So it was a real pleasure the other day to see the laziness revealed in some code, and for once not have this as the result of protracted debugging.  I was so taken aback that I'm sharing the experience.

<h1>Quicksort</h1>
<h2>The Algo</h2>
We all know the <a href="http://en.wikipedia.org/wiki/Quicksort">algorithm</a>, and <a href="http://bilfp.wikidot.com/why-functional-programming-matters">here's</a> a pretty Clojure implementation:
<pre class="brush:Clojure">
(defn qsort [[pivot & tail]]