Harmony: implement Math.trunc.

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 11 matching lines @@
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 'use strict';
 
 // ES6 draft 09-27-13, section 20.2.2.28.
 function MathSign(x) {
-  if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
+  x = TO_NUMBER_INLINE(x);
   if (x > 0) return 1;
   if (x < 0) return -1;
   if (x === 0) return x;
   return NAN;
 }
 
 
+// ES6 draft 09-27-13, section 20.2.2.34.
+function MathTrunc(x) {
+  x = TO_NUMBER_INLINE(x);
+  if (x > 0) return MathFloor(x);
+  if (x < 0) return MathCeil(x);
+  if (x === 0) return x;
+  return NAN;
+}
+
+
 function ExtendMath() {
   %CheckIsBootstrapping();
 
   // Set up the non-enumerable functions on the Math object.
   InstallFunctions($Math, DONT_ENUM, $Array(
-    "sign", MathSign
+    "sign", MathSign,
+    "trunc", MathTrunc
   ));
 }
 
 ExtendMath();