Add Euclidean algorithm in Ruby (#447)

* Add code

* Add it to the page

* Add absolute value, about to update .md file

* Updated line numbers

* Factorized arguments for clarity

Author: Nic Hartley

contents/euclidean_algorithm/code/ruby/euclidean.rb

@@ -0,0 +1,25 @@
+def gcd_mod(a, b)
+	a = a.abs
+	b = b.abs
+	a, b = b, a%b until b.zero?
+	a
+end
+ 
+def gcd_minus(a, b)
+	a = a.abs
+	b = b.abs
+	until a == b
+		if a > b
+			a -= b
+		else
+			b -= a
+		end
+	end
+	a
+end
+ 
+p gcd_mod(12 * 6, 12 * 4) #=> 12
+p gcd_mod(9 * 667, 9 * 104) #=> 9
+
+p gcd_minus(12 * 6, 12 * 4) #=> 12
+p gcd_minus(9 * 667, 9 * 104) #=> 9

contents/euclidean_algorithm/euclidean_algorithm.md

@@ -45,6 +45,8 @@ The algorithm is a simple way to find the *greatest common divisor* (GCD) of two
 [import:3-8, lang="scala"](code/scala/euclidean.scala)
 {% sample lang="racket" %}
 [import:3-14, lang="lisp"](code/racket/euclidean_algorithm.rkt)
+{% sample lang="ruby" %}
+[import:8-19, lang="ruby"](code/ruby/euclidean.rb)
 {% sample lang="st" %}
 [import:1-13, lang="smalltalk"](code/smalltalk/euclid.st)
 {% endmethod %}
@@ -98,6 +100,8 @@ Modern implementations, though, often use the modulus operator (%) like so
 [import:10-14, lang="scala"](code/scala/euclidean.scala)
 {% sample lang="racket" %}
 [import:16-24, lang="lisp"](code/racket/euclidean_algorithm.rkt)
+{% sample lang="ruby" %}
+[import:1-6, lang="ruby"](code/ruby/euclidean.rb)
 {% sample lang="st" %}
 [import:15-25, lang="smalltalk"](code/smalltalk/euclid.st)
 {% endmethod %}
@@ -156,6 +160,8 @@ The Euclidean Algorithm is truly fundamental to many other algorithms throughout
 [import, lang="scala"](code/scala/euclidean.scala)
 {% sample lang="racket" %}
 [import, lang="lisp"](code/racket/euclidean_algorithm.rkt)
+{% sample lang="ruby" %}
+[import, lang="ruby"](code/ruby/euclidean.rb)
 {% sample lang="st" %}
 [import, lang="smalltalk"](code/smalltalk/euclid.st)
 {% endmethod %}