Lisp bogo sort (#512)

* First working version of bogo sort in lisp

* FIxed the sortedp to see two equal items as sorted.

* Added lisp implementation to the .md file

* Cleaned up the shuffle method

Author: Trashtalk217

contents/bogo_sort/bogo_sort.md

@@ -55,6 +55,8 @@ In code, it looks something like this:
 [import:3-8, lang:"lisp"](code/racket/bogo_sort.rkt)
 {% sample lang="st" %}
 [import:2-6, lang:"st"](code/smalltalk/bogosort.st)
+{% sample lang="lisp" %}
+[import:20-24, lang:"lisp"](code/lisp/bogo-sort.lisp)
 {% endmethod %}
 
 That's it.
@@ -109,6 +111,8 @@ We are done here!
 [import, lang:"lisp"](code/racket/bogo_sort.rkt)
 {% sample lang="st" %}
 [import, lang:"st"](code/smalltalk/bogosort.st)
+{% sample lang="lisp" %}
+[import, lang:"lisp"](code/lisp/bogo-sort.lisp)
 {% endmethod %}
 
 

contents/bogo_sort/code/lisp/bogo-sort.lisp

@@ -0,0 +1,26 @@
+;;;; Bogo sort implementation
+
+(defun sortedp (list)
+  "Checks if a list is sorted"
+  (if (< (length list) 2)
+      t
+      (if (<= (first list) (second list))
+          (sortedp (rest list))
+          nil)))
+
+(defun shuffle (list)
+  "Returns a shuffled list using the Fisher-Yates method"
+  (loop for i from (1- (length list)) downto 0
+    do
+      (rotatef 
+        (nth i list)
+        (nth (random (1+ i)) list))
+    finally (return list)))
+
+(defun bogo-sort (list)
+  "Sorts a given list (eventually)"
+  (if (sortedp list)
+      list
+      (bogo-sort (shuffle list))))
+
+(print (bogo-sort (list 1 3 2 4)))