From a8dc9b36bb1eab2506324d05cf0113914c98565c Mon Sep 17 00:00:00 2001
From: Colin Jones <trptcolin@gmail.com>
Date: Tue, 9 Nov 2010 20:19:10 -0600
Subject: [PATCH] Refs. We has them.

---
 src/koans/refs.clj            | 27 +++++++++++++++++++++++++++
 src/path_to_answer_sheet.clj  |  6 ++++++
 src/path_to_enlightenment.clj |  3 ++-
 3 files changed, 35 insertions(+), 1 deletion(-)
 create mode 100644 src/koans/refs.clj

diff --git a/src/koans/refs.clj b/src/koans/refs.clj
new file mode 100644
index 0000000..1d57cb9
--- /dev/null
+++ b/src/koans/refs.clj
@@ -0,0 +1,27 @@
+(def the-world (ref "hello"))
+
+(meditations
+  "In the beginning, there was a word"
+  (= __ (deref the-world))
+
+  "You can get the word more succinctly, but it's the same"
+  (= __ @the-world)
+
+  "You can be the change you wish to see in the world."
+  (= __ (do
+          (dosync (ref-set the-world "better"))
+          @the-world))
+
+  "Alter where you need not replace"
+  (= __ (let [exclamator (fn [x] (str x "!"))]
+          (dosync
+            (alter the-world exclamator)
+            (alter the-world exclamator)
+            (alter the-world exclamator))
+          @the-world))
+
+  "Though you should keep transactions as short as possible"
+  (= "better!!!!!!" (letfn [(exclamator [x] (str x "!"))]
+          (dosync
+            (alter the-world ___))
+          @the-world)))
diff --git a/src/path_to_answer_sheet.clj b/src/path_to_answer_sheet.clj
index 6bdb9dd..8f382d6 100644
--- a/src/path_to_answer_sheet.clj
+++ b/src/path_to_answer_sheet.clj
@@ -111,6 +111,12 @@
                                  (repeat " "))))
                           '{:original-parts full-name
                             :named-parts {:first first-name :last last-name}} ]}
+   "refs" {"__" ["\"hello\""
+                 "\"hello\""
+                 "\"better\""
+                 "\"better!!!\""
+                 ]
+           "___" ['(comp exclamator exclamator exclamator)]}
    })
 
 (defn replace-with [s k replacements]
diff --git a/src/path_to_enlightenment.clj b/src/path_to_enlightenment.clj
index 36df1a3..0475659 100644
--- a/src/path_to_enlightenment.clj
+++ b/src/path_to_enlightenment.clj
@@ -27,7 +27,8 @@
       "sequence_comprehensions"
       "partial_functions"
       "recursion"
-      "destructuring"])
+      "destructuring"
+      "refs"])
 
 (defn run []
   (apply load (doall (map (partial str "koans/") ordered-koans)))