adding sequence comprehensions and a 3-argument equality

koans/about_equalities.clj

@@ -1,9 +1,12 @@
 (meditations
  "We shall contemplate truth by testing reality, via equality."
  (= true false)
- 
+
  "To understand reality, we must compare our expectations against reality."
  (= 0 (+ 1 1))
 
  "Sometimes we will ask you to fill in the values"
- (= __ (+ 1 1)))
+ (= __ (+ 1 1))
+
+ "You can test equality of many things"
+ (= (+ 3 4) __ (+ 2 _)))

koans/about_sequence_comprehensions.clj

@@ -0,0 +1,32 @@
+(meditations
+  "Sequence comprehensions can bind each element in turn to a symbol"
+  (= __
+     (for [index (range 6)]
+       index))
+
+  "They can easily emulate mapping"
+  (= '(0 1 4 9 16 25)
+     (map (fn [index] (* index index))
+          (range 6))
+     (for [index (range 6)]
+       __))
+
+  "And also filtering"
+  (= '(1 3 5 7 9)
+     (filter odd? (range 10))
+     (for [index __ :when (odd? index)]
+       index))
+
+  "And they trivially allow combinations of the two transformations"
+  (= '(1 9 25 49 81)
+     (map (fn [index] (* index index))
+          (filter odd? (range 10)))
+     (for [index (range 10) :when __]
+       __))
+
+  "More complex transformations can be formed with multiple binding forms"
+  (= [[:top :left] [:top :middle] [:top :right]
+      [:middle :left] [:middle :middle] [:middle :right]
+      [:bottom :left] [:bottom :middle] [:bottom :right]]
+     (for [row [:top :middle :bottom] column [:left :middle :right]]
+          __)))

koans/path_to_enlightenment.clj

@@ -20,4 +20,5 @@
 (load "about_conditionals")
 (load "about_higher_order_functions")
 (load "about_runtime_polymorphism")
+(load "about_sequence_comprehensions")
 (println "You have acheived clojure enlightenment. Namaste.")