Harmony: implement Math.log2 and Math.log10.

src/harmony-math.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 92 matching lines @@
 function MathAtanh(x) {
   if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
   // Idempotent for +/-0.
   if (x === 0) return x;
   // Returns NaN for NaN and +/- Infinity.
   if (!NUMBER_IS_FINITE(x)) return NAN;
   return 0.5 * MathLog((1 + x) / (1 - x));
 }
 
 
+//ES6 draft 09-27-13, section 20.2.2.21.
+function MathLog10(x) {
+  return MathLog(x) * 0.434294481903251828;  // log10(x) = log(x)/log(10).
+}
+
+
+//ES6 draft 09-27-13, section 20.2.2.22.
+function MathLog2(x) {
+  return MathLog(x) * 1.442695040888963407;  // log2(x) = log(x)/log(2).
+}
+
+
 function ExtendMath() {
   %CheckIsBootstrapping();
 
   // Set up the non-enumerable functions on the Math object.
   InstallFunctions($Math, DONT_ENUM, $Array(
     "sign", MathSign,
     "trunc", MathTrunc,
     "sinh", MathSinh,
     "cosh", MathCosh,
     "tanh", MathTanh,
     "asinh", MathAsinh,
     "acosh", MathAcosh,
-    "atanh", MathAtanh
+    "atanh", MathAtanh,
+    "log10", MathLog10,
+    "log2", MathLog2
   ));
 }
 
 ExtendMath();