Harmony: implement Math.trunc.

src/harmony-math.js

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-Object.defineProperty(this, "x", { writable:true });
+'use strict';
 
-function s(v) {
-  v.x = 1;
+// ES6 draft 09-27-13, section 20.2.2.28.
+function MathSign(x) {
+  if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
+  if (x > 0) return 1;
+  if (x < 0) return -1;
+  if (x === 0) return x;
+  return NAN;
 }
 
-function s_strict(v) {
-  "use strict";
-  v.x = 1;
+
+// ES6 draft 09-27-13, section 20.2.2.34.
+function MathTrunc(x) {
+  if (!IS_NUMBER(x)) x = NonNumberToNumber(x);

[Dmitry Lomov (no reviews), 2013/10/21 07:01:28]

Replace with TO_NUMBER_INLINE

+  if (x > 0) return MathFloor(x);
+  if (x < 0) return MathCeil(x);
+  if (x === 0) return x;
+  return NAN;
 }
 
-function c(p) {
-  return {__proto__: p};
+
+function ExtendMath() {
+  %CheckIsBootstrapping();
+
+  // Set up the non-enumerable functions on the Math object.
+  InstallFunctions($Math, DONT_ENUM, $Array(
+    "sign", MathSign,
+    "trunc", MathTrunc
+  ));
 }
 
-var o1 = c(this);
-var o2 = c(this);
-
-// Initialize the store IC.
-s(c(this));
-s(c(this));
-s_strict(c(this));
-s_strict(c(this));
-
-// Make x non-writable.
-Object.defineProperty(this, "x", { writable:false, value:5 });
-
-// Verify that direct setting fails.
-o1.x = 20;
-assertEquals(5, o1.x);
-
-// Verify that setting through the IC fails.
-s(o2);
-assertEquals(5, o2.x);
-assertThrows("s_strict(o2);", TypeError);
+ExtendMath();