From cdd46053a96d4215fb12ffa82114249da6b11e66 Mon Sep 17 00:00:00 2001
From: Kenneth Kostresevic <kenneth.kostresevic@verybigthings.com>
Date: Thu, 16 Dec 2021 15:56:29 +0100
Subject: [PATCH 1/3] Solve recursion

---
 src/koans/14_recursion.clj | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/koans/14_recursion.clj b/src/koans/14_recursion.clj
index ca29784..d108809 100644
--- a/src/koans/14_recursion.clj
+++ b/src/koans/14_recursion.clj
@@ -3,21 +3,27 @@
 
 (defn is-even? [n]
   (if (= n 0)
-    __
-    (___ (is-even? (dec n)))))
+    true
+    (not (is-even? (dec n)))))
 
 (defn is-even-bigint? [n]
   (loop [n   n
          acc true]
     (if (= n 0)
-      __
+      acc
       (recur (dec n) (not acc)))))
 
 (defn recursive-reverse [coll]
-  __)
+  (loop [coll coll  acc '()]
+    (if (= coll [])
+      acc
+      (recur (rest coll)  (conj acc (first coll))))))
 
 (defn factorial [n]
-  __)
+  (loop [n n acc n]
+    (if (= n 1)
+      acc
+      (recur (dec n) (* acc (dec n))))))
 
 (meditations
   "Recursion ends with a base case"

From 4bd3bc9a72efcb8a219fb43f4e3349cd46e838a1 Mon Sep 17 00:00:00 2001
From: Kenneth Kostresevic <kenneth.kostresevic@verybigthings.com>
Date: Fri, 17 Dec 2021 13:02:05 +0100
Subject: [PATCH 2/3] Improve recursive-reverse

---
 src/koans/14_recursion.clj | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/koans/14_recursion.clj b/src/koans/14_recursion.clj
index d108809..5e05015 100644
--- a/src/koans/14_recursion.clj
+++ b/src/koans/14_recursion.clj
@@ -14,10 +14,10 @@
       (recur (dec n) (not acc)))))
 
 (defn recursive-reverse [coll]
-  (loop [coll coll  acc '()]
-    (if (= coll [])
-      acc
-      (recur (rest coll)  (conj acc (first coll))))))
+  (loop [[head & tail] coll new-coll '()]
+    (if-not head
+      new-coll
+      (recur tail (conj new-coll head)))))
 
 (defn factorial [n]
   (loop [n n acc n]

From 807e32abbb2599c3848eb719e87db47fcfe9efc4 Mon Sep 17 00:00:00 2001
From: Kenneth Kostresevic <kenneth.kostresevic@verybigthings.com>
Date: Fri, 17 Dec 2021 13:03:37 +0100
Subject: [PATCH 3/3] Avoid extra decrementation in factorial

---
 src/koans/14_recursion.clj | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/koans/14_recursion.clj b/src/koans/14_recursion.clj
index 5e05015..81abc0c 100644
--- a/src/koans/14_recursion.clj
+++ b/src/koans/14_recursion.clj
@@ -20,10 +20,10 @@
       (recur tail (conj new-coll head)))))
 
 (defn factorial [n]
-  (loop [n n acc n]
+  (loop [n n acc 1]
     (if (= n 1)
       acc
-      (recur (dec n) (* acc (dec n))))))
+      (recur (dec n) (* acc n)))))
 
 (meditations
   "Recursion ends with a base case"