make sure the scheduled executor uses daemon threads

project.clj

@@ -1,4 +1,4 @@
-(defproject lamina "0.4.1-beta1"
+(defproject lamina "0.4.1-beta2"
   :description "event-driven data structures for clojure"
   :dependencies [[org.clojure/clojure "1.3.0"]
                  [org.clojure/tools.logging "0.2.3"]

src/lamina/core/timer.clj

@@ -12,10 +12,16 @@
     [java.util.concurrent
      ScheduledThreadPoolExecutor
      TimeUnit
-     TimeoutException]))
+     TimeoutException
+     ThreadFactory]))
 
 (def delayed-executor
-  (ScheduledThreadPoolExecutor. (.availableProcessors (Runtime/getRuntime))))
+  (ScheduledThreadPoolExecutor.
+    (.availableProcessors (Runtime/getRuntime))
+    (reify ThreadFactory
+      (newThread [_ f]
+        (doto (Thread. f)
+          (.setDaemon true))))))
 
 (defn delay-invoke [f delay]
   (.schedule

src/lamina/core/watch.clj

@@ -0,0 +1,54 @@
+;;   Copyright (c) Zachary Tellman. 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.html at the root of this distribution.
+;;   By using this software in any fashion, you are agreeing to be bound by
+;;   the terms of this license.
+;;   You must not remove this notice, or any other, from this software.
+
+(ns lamina.core.watch
+  (:use
+    [lamina.core channel utils])
+  (:import
+    [java.lang.ref
+     WeakReference]
+    [java.util
+     Collections
+     WeakHashMap]))
+
+;;;
+
+(deftype WeakRef [^WeakReference ref]
+  clojure.lang.IDeref
+  (deref [_] (.get ref)))
+
+(defn weak-ref [x]
+  (WeakRef. x))
+
+;;;
+
+(defprotocol Watcher
+  (examine [_])
+  (update [_ val]))
+
+(defn ref-watcher [reference callback]
+  (let [r (weak-ref reference)
+        tl (ThreadLocal.)
+        val (atom @reference)]
+    (reify Watcher
+      (examine [_]
+        (when-let [r @r]
+          (loop [x @val, y @r]
+            (if-not (= x y)
+              (if (compare-and-set! val x y)
+                (callback y)
+                (recur @val @r)))))))))
+
+(defn watcher-channel [watchable]
+  (let [ch (channel @watchable)
+        k (gensym "watcher-channel")]
+    (add-watch watchable k
+      (fn [_ _ _ x] (enqueue ch x)))
+    (on-closed ch
+      #(remove-watch watchable k))
+    ch))