Mercurial > lasercutter
comparison src/clojure/contrib/probabilities/random_numbers.clj @ 10:ef7dbbd6452c
added clojure source goodness
| author | Robert McIntyre <rlm@mit.edu> |
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| date | Sat, 21 Aug 2010 06:25:44 -0400 |
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| 9:35cf337adfcf | 10:ef7dbbd6452c |
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| 1 ;; Random number generators | |
| 2 | |
| 3 ;; by Konrad Hinsen | |
| 4 ;; last updated May 3, 2009 | |
| 5 | |
| 6 ;; Copyright (c) Konrad Hinsen, 2009. All rights reserved. The use | |
| 7 ;; and distribution terms for this software are covered by the Eclipse | |
| 8 ;; Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php) | |
| 9 ;; which can be found in the file epl-v10.html at the root of this | |
| 10 ;; distribution. By using this software in any fashion, you are | |
| 11 ;; agreeing to be bound by the terms of this license. You must not | |
| 12 ;; remove this notice, or any other, from this software. | |
| 13 | |
| 14 (ns | |
| 15 ^{:author "Konrad Hinsen" | |
| 16 :doc "Random number streams | |
| 17 | |
| 18 This library provides random number generators with a common | |
| 19 stream interface. They all produce pseudo-random numbers that are | |
| 20 uniformly distributed in the interval [0, 1), i.e. 0 is a | |
| 21 possible value but 1 isn't. For transformations to other | |
| 22 distributions, see clojure.contrib.probabilities.monte-carlo. | |
| 23 | |
| 24 At the moment, the only generator provided is a rather simple | |
| 25 linear congruential generator."} | |
| 26 clojure.contrib.probabilities.random-numbers | |
| 27 (:refer-clojure :exclude (deftype)) | |
| 28 (:use [clojure.contrib.types :only (deftype)]) | |
| 29 (:use [clojure.contrib.stream-utils :only (defstream)]) | |
| 30 (:use [clojure.contrib.def :only (defvar)])) | |
| 31 | |
| 32 ;; Linear congruential generator | |
| 33 ;; http://en.wikipedia.org/wiki/Linear_congruential_generator | |
| 34 | |
| 35 (deftype ::lcg lcg | |
| 36 "Create a linear congruential generator" | |
| 37 {:arglists '([modulus multiplier increment seed])} | |
| 38 (fn [modulus multiplier increment seed] | |
| 39 {:m modulus :a multiplier :c increment :seed seed}) | |
| 40 (fn [s] (map s (list :m :a :c :seed)))) | |
| 41 | |
| 42 (defstream ::lcg | |
| 43 [lcg-state] | |
| 44 (let [{m :m a :a c :c seed :seed} lcg-state | |
| 45 value (/ (float seed) (float m)) | |
| 46 new-seed (rem (+ c (* a seed)) m)] | |
| 47 [value (assoc lcg-state :seed new-seed)])) | |
| 48 | |
| 49 ;; A generator based on Clojure's built-in rand function | |
| 50 ;; (and thus random from java.lang.Math) | |
| 51 ;; Note that this generator uses an internal mutable state. | |
| 52 ;; | |
| 53 ;; The state is *not* stored in the stream object and can thus | |
| 54 ;; *not* be restored! | |
| 55 | |
| 56 (defvar rand-stream (with-meta 'rand {:type ::rand-stream}) | |
| 57 "A random number stream based on clojure.core/rand. Note that this | |
| 58 generator uses an internal mutable state. The state is thus not stored | |
| 59 in the stream object and cannot be restored.") | |
| 60 | |
| 61 (defstream ::rand-stream | |
| 62 [dummy-state] | |
| 63 [(rand) dummy-state]) |