├── LICENSE ├── project.clj └── src └── async_mu_kanren └── core.clj /LICENSE: -------------------------------------------------------------------------------- 1 | THE ACCOMPANYING PROGRAM IS PROVIDED UNDER THE TERMS OF THIS ECLIPSE PUBLIC 2 | LICENSE ("AGREEMENT"). ANY USE, REPRODUCTION OR DISTRIBUTION OF THE PROGRAM 3 | CONSTITUTES RECIPIENT'S ACCEPTANCE OF THIS AGREEMENT. 4 | 5 | 1. DEFINITIONS 6 | 7 | "Contribution" means: 8 | 9 | a) in the case of the initial Contributor, the initial code and 10 | documentation distributed under this Agreement, and 11 | 12 | b) in the case of each subsequent Contributor: 13 | 14 | i) changes to the Program, and 15 | 16 | ii) additions to the Program; 17 | 18 | where such changes and/or additions to the Program originate from and are 19 | distributed by that particular Contributor. A Contribution 'originates' from 20 | a Contributor if it was added to the Program by such Contributor itself or 21 | anyone acting on such Contributor's behalf. 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Each party waives its rights to a jury trial 214 | in any resulting litigation. 215 | -------------------------------------------------------------------------------- /project.clj: -------------------------------------------------------------------------------- 1 | (defproject async-mu-kanren "0.1.0-SNAPSHOT" 2 | :description "FIXME: write description" 3 | :url "http://example.com/FIXME" 4 | :license {:name "Eclipse Public License" 5 | :url "http://www.eclipse.org/legal/epl-v10.html"} 6 | :dependencies [[org.clojure/clojure "1.6.0"] 7 | [org.clojure/core.async "0.1.0-SNAPSHOT"] 8 | [org.clojure/core.logic "0.8.7"]]) 9 | -------------------------------------------------------------------------------- /src/async_mu_kanren/core.clj: -------------------------------------------------------------------------------- 1 | (ns async-mu-kanren.core 2 | (:refer-clojure :exclude [conj disj merge ==]) 3 | (:require [clojure.core.async :refer [! chan close! !! alts!!] :as async] 4 | [clojure.core.async.impl.protocols :as impl] 5 | [clojure.core.logic :as l] 6 | [clojure.core.logic.protocols :as lp])) 7 | 8 | ;; An implementation of muKanren (http://webyrd.net/scheme-2013/papers/HemannMuKanren2013.pdf) 9 | ;; using core.async channels (CSP) instead of lazy streams and using CSP processes instead 10 | ;; of monads 11 | 12 | ;; Helper to print out stacktraces when gos fail 13 | (defmacro go [& body] 14 | `(async/go (try 15 | ~@body 16 | (catch Throwable ex# 17 | (clojure.stacktrace/print-stack-trace ex#) 18 | (println "--"))))) 19 | 20 | ;; Goals will return a single channel. Items put into this channel will be processed by the goal 21 | ;; and then the result can be taken from this same channel. Notice this is completely different 22 | ;; from standard CSP channels, which only allow simplex communication. We're going to leverage 23 | ;; core.async's interfaces to create a duplex channel. 24 | 25 | ;; This function will return two channel like things items put into the first channel can be read 26 | ;; from the second and vice-versa. 27 | 28 | (defn duplex-pipe 29 | "Defines two connected duplex channels" 30 | [] 31 | (let [c-> (chan 1) 32 | c<- (chan 1)] 33 | 34 | [(reify 35 | impl/WritePort 36 | (put! [this val handler] 37 | (impl/put! c-> val handler)) 38 | impl/ReadPort 39 | (take! [this handler] 40 | (impl/take! c<- handler)) 41 | impl/Channel 42 | (close! [this] 43 | (impl/close! c->)) 44 | (closed? [this] 45 | (impl/closed? c->))) 46 | 47 | (reify 48 | impl/WritePort 49 | (put! [this val handler] 50 | (impl/put! c<- val handler)) 51 | impl/ReadPort 52 | (take! [this handler] 53 | (impl/take! c-> handler)) 54 | impl/Channel 55 | (close! [this] 56 | (impl/close! c<-)) 57 | (closed? [this] 58 | (impl/closed? c<-)))])) 59 | 60 | ;; Logging helpers, call log to print data to the console without the output 61 | ;; getting clobbered by other processes 62 | (let [c (chan)] 63 | (go (loop [] 64 | (println (!! c (vec args)))) 68 | 69 | ;; muKanren defines conj as a goal that takes two goals, passing results to the second 70 | ;; only if the fist passes. If we assume goals will not return a value if the goal fails, 71 | ;; then we can easily define conj in terms of pipe. 72 | (defn conj 73 | ([g1] g1) 74 | ([g1 g2] 75 | (let [[s ret] (duplex-pipe)] 76 | (async/pipe s g1) 77 | (async/pipe g1 g2) 78 | (async/pipe g2 s) 79 | ret)) 80 | ([g1 g2 & more] 81 | (conj g1 (apply conj g1 more)))) 82 | 83 | ;; disj is defined as a parallel trying of two goals. Core.async supplies broadcast facilities 84 | ;; in the form of `mux` we will leverage these and pipe the resuls form the gos to the output 85 | (defn disj [& goals] 86 | (let [[s ret] (duplex-pipe) 87 | m (async/mult s)] 88 | (doseq [g goals] 89 | (async/tap m g) 90 | (async/pipe g s)) 91 | ret)) 92 | 93 | ;; unification goal. Originally this code used a custom unifier as specified in the paper above, 94 | ;; instead we now leverage the unification engine of Core.Logic. This this allows us to take advantage 95 | ;; of things like LCons with minimal effort. 96 | 97 | ;; the unification gal can be define din therms of pipe map and removal of nils. 98 | (defn == [a b] 99 | (let [[s ret] (duplex-pipe)] 100 | (async/pipe 101 | s 102 | (async/map> (fn [s] 103 | #_(log [s a b]) 104 | (l/unify s a b)) 105 | (async/remove> nil? s))) 106 | ret)) 107 | 108 | ;; fresh defines lvars in an outer let and then simply applies conj to all the goals in the body 109 | (defmacro fresh [lvars & goals] 110 | `(let [~@(vec (mapcat (fn [var] 111 | `[~var (l/lvar ~(name var))]) 112 | lvars))] 113 | ~(if (> (count goals) 1) 114 | `(conj ~@goals) 115 | (first goals)))) 116 | 117 | ;; conde is a disj wrapping bodies wrapped in conj 118 | (defn conde [& goals] 119 | (apply disj (map (partial apply conj) goals))) 120 | 121 | ;; given a set of lvars, pull walk them from the substitution map and return a seq of the resulting values. 122 | (defn -run-chan [lvars g] 123 | (let [[s ret] (duplex-pipe)] 124 | (async/pipe s g) 125 | (async/pipe (async/map< (fn [s] 126 | (map #(lp/walk s %) lvars)) 127 | g) 128 | s) 129 | ret)) 130 | 131 | ;; like core.logic's run-lazy but returns a channel 132 | (defmacro run-chan [lvars & goals] 133 | `(let [lvars# ~(vec (map (fn [var] 134 | `(l/lvar (gensym ~(name var)))) 135 | lvars)) 136 | ~lvars lvars# 137 | r# ~(if (> (count goals) 1) 138 | `(conj ~@goals) 139 | (first goals))] 140 | (-run-chan lvars# r#))) 141 | 142 | (defn close-after [msec c] 143 | (go (!! r# l/empty-s) 152 | (! c x)))) 234 | 235 | ;; Non relational. Given a lvar 'max' unify with 0-max, but do it slowly, 236 | ;; one unification a second. 237 | (defn upto [max out] 238 | (let [[s ret] (duplex-pipe)] 239 | (sink s (fn [a] 240 | (let [max (lp/walk a max)] 241 | (assert (not (l/lvar? max)) "max must be bound") 242 | (->> (range max) 243 | (map (partial l/unify a out)) 244 | (onto-chan-limit s 1000))))) 245 | ret)) 246 | 247 | 248 | ;; Notice how the results slowly arrive, even though the CPU is idle 249 | (let [rc (run-chan [q] 250 | (upto 100 q))] 251 | (>!! rc l/empty-s) 252 | (dotimes [x 10] 253 | (println (