From a260dfe333b765c91522c70869ae7a0dec1dc306 Mon Sep 17 00:00:00 2001
From: Anton Yefremov <anton.yefremov@gmail.com>
Date: Fri, 10 Feb 2017 21:10:33 +0200
Subject: [PATCH] Implement coprime algorithm

---
 lib/iterative/coprime.js           | 35 ++++++++++++++++++++++++++++++
 lib/iterative/test/coprime-test.js | 11 ++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 lib/iterative/coprime.js
 create mode 100644 lib/iterative/test/coprime-test.js

diff --git a/lib/iterative/coprime.js b/lib/iterative/coprime.js
new file mode 100644
index 0000000..b5a750b
--- /dev/null
+++ b/lib/iterative/coprime.js
@@ -0,0 +1,35 @@
+
+/**
+ * Expose `coprime`.
+ */
+
+module.exports = coprime;
+
+/**
+ * Test whether `a` and `b` are coprime numbers.
+ *
+ * @param {number} a Positive number value.
+ * @param {number} b Positive number value.
+ * @returns {boolean}
+ * @example
+ *
+ * coprime(13, 27);
+ * // => false
+ *
+ * coprime(20536, 7826);
+ * // => false
+ */
+
+function coprime(a, b) {
+  // subtraction-based version of Euclid's algorithm
+  while (a !== b) {
+    if (a > b) {
+      a -= b;
+    } else {
+      b -= a;
+    }
+  }
+  // two numbers are coprime if their greatest
+  // common divisor equals 1
+  return a === 1;
+}
diff --git a/lib/iterative/test/coprime-test.js b/lib/iterative/test/coprime-test.js
new file mode 100644
index 0000000..e21ea1c
--- /dev/null
+++ b/lib/iterative/test/coprime-test.js
@@ -0,0 +1,11 @@
+var test = require('tape');
+var coprime = require('../coprime');
+
+test('coprime(a, b)', function (t) {
+  t.equal(coprime(1, 1), true, 'should return `true`');
+  t.equal(coprime(1, 2), true, 'should return `true`');
+  t.equal(coprime(2, 2), false, 'should return `false`');
+  t.equal(coprime(13, 27), true, 'should return `true`');
+  t.equal(coprime(20536, 7826), false, 'should return `false`');
+  t.end();
+});