From c8f711e209a8987c80920ba07d392ab0f878d40a Mon Sep 17 00:00:00 2001
From: Ignacy Moryc <imoryc@gmail.com>
Date: Sun, 23 Sep 2012 15:38:31 +0200
Subject: [PATCH] Use let scope to bing the agent

---
 src/koans/21_agents.clj | 49 +++++++++++++++++++++--------------------
 1 file changed, 25 insertions(+), 24 deletions(-)

diff --git a/src/koans/21_agents.clj b/src/koans/21_agents.clj
index 4b02fd1..2b70c70 100644
--- a/src/koans/21_agents.clj
+++ b/src/koans/21_agents.clj
@@ -1,31 +1,32 @@
-(def agent-example
-  "Agents provide shared access to mutable state."
-  (agent 10))
-
 (meditations
-  "Creating an Agent is as simple as assigning it a value"
-  (= __ (instance? clojure.lang.Agent agent-example))
+ (let [agent-example (agent 10)]
 
-  "To get agent's value you dereference it"
-  (= __ @agent-example)
+   "Creating an Agent is as simple as assigning it a value"
+   (= __ (instance? clojure.lang.Agent agent-example))
 
-  "To change agent's value you use send function - you pass action and action's arguments to it.
+   "To get agent's value you dereference it"
+   (= __ @agent-example)
+
+   "To change agent's value you use send function - you pass action and action's arguments to it.
    Send function, returns immediately, but the action is prccessed in a separate thread and it's the result,
    of that action that gets assigned to agent's state"
-  (= __ (do
-          (send agent-example + 2)
-          @agent-example))
+   (= __ (do
+           (send agent-example + 2)
+           @agent-example))
 
-  "You can't just send a value to agent"
-  (= __ (do
-          (set-error-mode! agent-example :continue)
-          (send agent-example 20)
-          @agent-example))
+   "You can't just send a value to agent"
+   (= __ (do
+           (set-error-mode! agent-example :continue)
+           (send agent-example 20)
+           @agent-example))
 
-  "You can create validations for states that agent is allowed to take"
-  (= __ (do
-          (set-validator! agent-example #(even? %))
-          (try
-            (send agent-example + 1)
-            (catch IllegalStateException e))
-          @agent-example)))
+   "You can create validations for states that agent is allowed to take"
+   (= __ (do
+           (set-validator! agent-example #(even? %))
+           (try
+             (send agent-example + 1)
+             (catch IllegalStateException e))
+           @agent-example))
+
+   "It's a good idea to clean up any not finished agents after you are done"
+   (shutdown-agents)))