diff options
Diffstat (limited to 'src/clojure/contrib/probabilities/dist.clj')
| -rw-r--r-- | src/clojure/contrib/probabilities/dist.clj | 17 |
1 files changed, 8 insertions, 9 deletions
diff --git a/src/clojure/contrib/probabilities/dist.clj b/src/clojure/contrib/probabilities/dist.clj index 4f9100fd..4c1d321f 100644 --- a/src/clojure/contrib/probabilities/dist.clj +++ b/src/clojure/contrib/probabilities/dist.clj @@ -1,7 +1,7 @@ ;; Finite probability distributions ;; by Konrad Hinsen -;; last updated January 30, 2009 +;; last updated February 18, 2009 ;; Copyright (c) Konrad Hinsen, 2009. All rights reserved. The use ;; and distribution terms for this software are covered by the Eclipse @@ -12,7 +12,6 @@ ;; remove this notice, or any other, from this software. (ns clojure.contrib.probabilities.dist - (:refer-clojure :exclude (sequence)) (:use clojure.contrib.monads clojure.contrib.macros clojure.contrib.monads clojure.contrib.def)) @@ -20,12 +19,12 @@ ; distributions (e.g. there is a finite number of possible value), which ; are represented as maps from values to probabilities. -(defmonad dist +(defmonad dist-m "Monad describing computations on fuzzy quantities, represented by a finite probability distribution for the possible values. A distribution is represented by a map from values to probabilities." [m-result (fn m-result-dist [v] - {v 1}) + {v 1}) m-bind (fn m-bind-dist [mv f] (letfn [add-prob [dist [x p]] (assoc dist x (+ (get dist x 0) p))] @@ -40,8 +39,8 @@ ; The function normalize takes this probability out of the distribution and ; re-distributes its weight over the valid values. -(defvar cond-dist - (maybe-t dist) +(defvar cond-dist-m + (maybe-t dist-m) "Variant of the dist monad that can handle undefined values.") ; Normalization @@ -100,7 +99,7 @@ :else (assoc dist v p))] (reduce add-choice {} (partition 2 choices)))) -(with-monad dist +(with-monad dist-m (defn certainly "Returns a distribution in which the single value v has probability 1." @@ -119,7 +118,7 @@ the predicate pred." [pred dist] (normalize-cond - (with-monad cond-dist + (with-monad cond-dist-m (m-bind dist (fn [v] (m-result (when (pred v) v))))))) ; Select (with equal probability) N items from a sequence @@ -130,7 +129,7 @@ (let [[h t] (split-at n xs)] (list (first t) (concat h (rest t))))) -(with-monad dist +(with-monad dist-m (defn- select-n [n xs] (letfn [select-1 [[s xs]] |