From f58864deda9e5bdceea530b8dfb3654a7a1fbd24 Mon Sep 17 00:00:00 2001
From: Colin Jones <trptcolin@gmail.com>
Date: Thu, 11 Feb 2010 12:13:55 +0800
Subject: [PATCH 1/2] adding about map/filter/reduce

---
 koans/about_higher_order_functions.clj | 32 ++++++++++++++++++++++++++
 koans/path_to_enlightenment.clj        |  1 +
 2 files changed, 33 insertions(+)
 create mode 100644 koans/about_higher_order_functions.clj

diff --git a/koans/about_higher_order_functions.clj b/koans/about_higher_order_functions.clj
new file mode 100644
index 0000000..fc9ea67
--- /dev/null
+++ b/koans/about_higher_order_functions.clj
@@ -0,0 +1,32 @@
+(meditations
+  "The map function relates a sequence to another"
+  (= [__ __ __] (map (fn [x] (* 4 x)) [1 2 3]))
+
+  "You may create that mapping"
+  (= [1 4 9 16 25] (map (fn [x] __) [1 2 3 4 5]))
+
+  "Or use the names of existing functions"
+  (= __ (map nil? [:a :b nil :c :d]))
+
+  "A filter can be strong"
+  (= __ (filter (fn [x] false) '(:anything :goes :here)))
+
+  "Or very weak"
+  (= '(:anything :goes :here) (filter (fn [x] __) '(:anything :goes :here)))
+
+  "Or somewhere in between"
+  (= [10 20 30] (filter (fn [x] __) [10 20 30 40 50 60 70 80]))
+
+  "Maps and filters may be combined"
+  (= [10 20 30] (map (fn [x] __) (filter (fn [x] __) [1 2 3 4 5 6 7 8])))
+
+  "Reducing can increase the result"
+  (= __ (reduce (fn [a b] (* a b)) [1 2 3 4]))
+
+  "You can start somewhere else"
+  (= 2400 (reduce (fn [a b] (* a b)) __ [1 2 3 4]))
+
+  "Numbers are not the only things one can reduce"
+  (= "longest" (reduce (fn [a b]
+                         (if (< __ __) b a))
+                       ["which" "word" "is" "longest"])))
diff --git a/koans/path_to_enlightenment.clj b/koans/path_to_enlightenment.clj
index 67dfb52..ee2d974 100644
--- a/koans/path_to_enlightenment.clj
+++ b/koans/path_to_enlightenment.clj
@@ -18,4 +18,5 @@
 (load "about_maps")
 (load "about_functions")
 (load "about_conditionals")
+(load "about_higher_order_functions")
 (println "You have acheived clojure enlightenment. Namaste.")

From 357b458241a297b8829b785dd44b80f9d2eafdfd Mon Sep 17 00:00:00 2001
From: Colin Jones <trptcolin@gmail.com>
Date: Sun, 14 Feb 2010 08:19:13 +0800
Subject: [PATCH 2/2] adding runtime polymorphism

---
 koans/about_runtime_polymorphism.clj | 35 ++++++++++++++++++++++++++++
 koans/path_to_enlightenment.clj      |  1 +
 2 files changed, 36 insertions(+)
 create mode 100644 koans/about_runtime_polymorphism.clj

diff --git a/koans/about_runtime_polymorphism.clj b/koans/about_runtime_polymorphism.clj
new file mode 100644
index 0000000..a8171ee
--- /dev/null
+++ b/koans/about_runtime_polymorphism.clj
@@ -0,0 +1,35 @@
+(defn hello
+  ([] "Hello World!")
+  ([a] (str "Hello, you silly " a "."))
+  ([a & more] (str "Hello to this group: "
+                   (apply str
+                          (interpose ", " (concat (list a) more)))
+                   "!")))
+
+(defmulti diet (fn [x] (:eater x)))
+(defmethod diet :herbivore [a] __)
+(defmethod diet :carnivore [a] __)
+(defmethod diet :default [a] __)
+
+(meditations
+  "Some functions can be used in different ways - with no arguments"
+  (= __ (hello))
+
+  "With one argument"
+  (= __ (hello "world"))
+
+  "Or with many arguments"
+  (= __
+     (hello "Peter" "Paul" "Mary"))
+
+  "Multimethods allow more complex dispatching"
+  (= "Bambi eats veggies."
+     (diet {:species "deer" :name "Bambi" :age 1 :eater :herbivore}))
+
+  "Different methods are used depending on the dispatch function result"
+  (= "Simba eats animals."
+     (diet {:species "lion" :name "Simba" :age 1 :eater :carnivore}))
+
+  "You may use a default method when no others match"
+  (= "I don't know what Rich Hickey eats."
+     (diet {:name "Rich Hickey"})))
diff --git a/koans/path_to_enlightenment.clj b/koans/path_to_enlightenment.clj
index ee2d974..450ef35 100644
--- a/koans/path_to_enlightenment.clj
+++ b/koans/path_to_enlightenment.clj
@@ -19,4 +19,5 @@
 (load "about_functions")
 (load "about_conditionals")
 (load "about_higher_order_functions")
+(load "about_runtime_polymorphism")
 (println "You have acheived clojure enlightenment. Namaste.")