Minor changes to euclidean algorithm implementation in Common Lisp

contents/euclidean_algorithm/code/clisp/euclidean.lisp

@@ -0,0 +1,31 @@
+;;;; Euclid algorithm implementation in Common Lisp
+
+(defun euclid-sub (a b)
+  "Finds the greatest common divsor for any two integers"
+  (euclid-sub* (abs a) (abs b)))
+
+(defun euclid-sub* (a b)
+  "Finds the greatest common divisor for any two positive integers"
+  (if (eq a b)
+      a
+      (if (> a b)
+        (euclid-sub* (- a b) b)
+        (euclid-sub* a (- b a)))))
+
+(defun euclid-mod (a b)
+  "Finds the greatest common divisor for any two integers"
+  (if (zerop b)
+      (abs a)
+      (euclid-mod b (mod a b))))
+
+(print (euclid-sub (* 64 67) (* 64 81)))
+(print (euclid-mod (* 128 12) (* 128 77)))
+
+; quick test
+(assert
+  (=  (euclid-sub (* 64 67) (* 64 81))
+      (gcd (* 64 67) (* 64 81))))
+
+(assert
+  (=  (euclid-mod (* 64 67) (* 64 81))
+      (gcd (* 64 67) (* 64 81))))

contents/euclidean_algorithm/euclidean_algorithm.md

@@ -20,7 +20,7 @@ The algorithm is a simple way to find the *greatest common divisor* (GCD) of two
 {% sample lang="js" %}
 [import:15-29, lang="javascript"](code/javascript/euclidean_example.js)
 {% sample lang="lisp" %}
-[import:3-12, lang="lisp"](code/clisp/euclidean_algorithm.lisp)
+[import:3-13, lang="lisp"](code/clisp/euclidean_algorithm.lisp)
 {% sample lang="py" %}
 [import:11-22, lang="python"](code/python/euclidean_example.py)
 {% sample lang="haskell" %}
@@ -97,7 +97,7 @@ Modern implementations, though, often use the modulus operator (%) like so
 {% sample lang="js" %}
 [import:1-13, lang="javascript"](code/javascript/euclidean_example.js)
 {% sample lang="lisp" %}
-[import:13-17, lang="lisp"](code/clisp/euclidean_algorithm.lisp)
+[import:15-19, lang="lisp"](code/clisp/euclidean_algorithm.lisp)
 {% sample lang="py" %}
 [import:1-9, lang="python"](code/python/euclidean_example.py)
 {% sample lang="haskell" %}