From aabc4f02ca49cb4e65debc79d50c24c1481a6e0a Mon Sep 17 00:00:00 2001
From: Eric Schulte <schulte.eric@gmail.com>
Date: Sun, 23 Jan 2011 11:09:54 -0700
Subject: [PATCH] multiple improvements based on Ken Wesson's comments

---
 src/propagator.clj | 44 +++++++++++++++++---------------------------
 1 file changed, 17 insertions(+), 27 deletions(-)

diff --git a/src/propagator.clj b/src/propagator.clj
index 6fcf7fd..65170f2 100644
--- a/src/propagator.clj
+++ b/src/propagator.clj
@@ -1,41 +1,31 @@
-
-(ns
-    #^{:author "Eric Schulte",
+(ns #^{:author "Eric Schulte",
        :license "GPLV3",
        :doc "Simple concurrent propagator system."}
   propagator
   (:use clojure.contrib.repl-utils clojure.contrib.math))
 
-(defmacro cell "Define a new cell."
-  [name state]
-  `(def ~name (agent ~state)))
-
 (defn set-cell "Set the value of a cell" [cell value]
-  (send cell (fn [_] value)))
-
-(defmacro propagator "Define a new propagator."
-  [name in-cells out-cells & body]
-  `(do
-     (defn ~(with-meta name
-              (assoc (meta name)
-                :in-cells in-cells :out-cells out-cells))
-       ~in-cells ~@body)
-     (doseq [cell# ~in-cells] (add-neighbor cell# ~name))
-     ~name))
+  (send cell (constantly value)))
 
 (defmacro run-propagator
   "Run a propagator, first collect the most recent values from all
 cells associated with the propagator, then evaluate."
   [propagator]
-  `(let [results# (apply ~propagator (map deref (:in-cells ^#'~propagator)))]
-     (doseq [cell# (:out-cells ^#'~propagator)]
+  `(let [results# (apply ~propagator (map deref (:in-cells (meta ~propagator))))]
+     (doseq [cell# (:out-cells (meta ~propagator))]
        (when (not (= @cell# results#))
-         (send cell# (fn [_#] results#))))
+         (set-cell cell# results#)))
      results#))
 
-(defmacro add-neighbor "Add a neighbor to the given cell."
-  [cell neighbor]
-  `(add-watcher
-    ~cell :send
-    (agent nil :validator (fn [_#] (do (future (run-propagator ~neighbor)) true)))
-    (fn [_# _#])))
+(defn add-neighbor "Add a neighbor to the given cell." [cell neighbor]
+  (add-watch cell nil (fn [_ _ _ _] (future (run-propagator neighbor)))))
+
+(defmacro defcell "Define a new cell." [name state]
+  `(def ~name (agent ~state)))
+
+(defmacro defpropagator "Define a new propagator."
+  [name in-cells out-cells & body]
+  `(let [v# (defn ~(vary-meta name assoc :in-cells in-cells :out-cells out-cells)
+              ~in-cells ~@body)]
+     (doseq [cell# ~in-cells] (add-neighbor cell# ~name))
+     v#))
-- 
2.11.4.GIT