Implement math.gcd in dart.

pkg/math/test/lcm_test.dart

Index: pkg/math/test/lcm_test.dart
diff --git a/pkg/math/test/lcm_test.dart b/pkg/math/test/lcm_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..8952938d7757c15d40a138e93c52756202243c1c
--- /dev/null
+++ b/pkg/math/test/lcm_test.dart
@@ -0,0 +1,70 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library math_test;
+import "package:expect/expect.dart";
+import 'dart:math';
+import 'package:math/math.dart';
+
+void testLcm() {
+  Expect.equals(0, lcm(0, 7));
+  Expect.equals(0, lcm(5, 0));
+  Expect.equals(0, lcm(-5, 0));
+  Expect.equals(0, lcm(0, 0));
+  Expect.equals(35, lcm(5, 7));
+  Expect.equals(36, lcm(12, 18));
+  Expect.equals(36, lcm(12, -18));
+  Expect.equals(36, lcm(-12, -18));
+  Expect.equals(36, lcm(18, 12));
+  Expect.equals(315, lcm(45, 105));
+
+  Expect.throws(() => lcm(0, null), (e) => e is ArgumentError);
+  Expect.throws(() => lcm(null, 0), (e) => e is ArgumentError);
+
+  // Cover all branches in Binary GCD implementation.
+  // 0 shared powers-of-two factors.
+  Expect.equals(28, lcm(2*2, 7));
+  // 1 shared power-of-two factor.
+  Expect.equals(28, lcm(2*2, 2*7));
+  // >1 shared powers-of-two factors.
+  Expect.equals(120, lcm(2*2*2*3, 2*2*2*5));
+
+  // 0 remaining powers-of-two in a.
+  Expect.equals(18, lcm(2*3, 2*3*3));
+  // 1 remaining power-of-two in a.
+  Expect.equals(36, lcm(2*2*3, 2*3*3));
+  // >1 remaining powers-of-two in a.
+  Expect.equals(144, lcm(2*2*2*2*3, 2*3*3));
+
+  // 0 remaining powers-of-two in b.
+  Expect.equals(18, lcm(2*3, 2*3*3));
+  // 1 remaining power-of-two in b.
+  Expect.equals(12, lcm(2*3, 2*2*3));
+  // >1 remaining powers-of-two in b.
+  Expect.equals(72, lcm(2*3, 2*2*2*3*3));
+
+  // Innermost 'if'
+  // a > b.
+  Expect.equals(60, lcm(2*2*3*5, 2*3));
+  // a == b.
+  Expect.equals(24, lcm(2*3, 2*2*2*3));
+  // a < b.
+  Expect.equals(84, lcm(2*3, 2*2*3*7));
+
+  // do while loop executions.
+  // Executed 1 time.
+  Expect.equals(24, lcm(2*3, 2*2*2*3));
+  // Executed >1 times.
+  Expect.equals(180, lcm(2*3*3, 2*2*3*5));
+
+  // Medium int (mint) arguments.
+  Expect.equals(pow(2, 62)*3, lcm(pow(2, 61)*3, pow(2,62)));
+  // 9079837958533 is the first prime after 2**48 / 31.
+  Expect.equals(31*37*9079837958533,
+    lcm(31*9079837958533, 37*9079837958533));
+}
+
+main() {
+  testLcm();
+}