Implement Object.is and Number.is[Finite,NaN] functions.

src/v8natives.js

 // Copyright 2012 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 1240 matching lines @@
   if (!IS_SPEC_OBJECT(obj)) {
     throw MakeTypeError("called_on_non_object", ["Object.isExtensible"]);
   }
   if (%IsJSProxy(obj)) {
     return true;
   }
   return %IsExtensible(obj);
 }
 
 
+// Harmony egal.
+function ObjectIs(obj1, obj2) {
+  if (obj1 === obj2) {

[arv (Not doing code reviews), 2012/03/13 05:15:49]

Why don't we use the SameValue function?

http://code.google.com/codesearch#OAMlx_jo-ck/src/v8/src/runtime.js&exact_pac...

[Michael Starzinger, 2012/03/13 09:02:08]

Yes we could use that function, but I didn't care much about making it perfect
because this is only an intermediate step. And frankly I didn't remember we had
SameValue(), I only remembered it's native counterpart JSObject::SameValue(). If
you are interested in the full story, here is how I want to proceed with the
egal operator implementation:

1) Have our backends generate optimized code for [[SameValue]] and expose it via
an %_SameValue() intrinsic.
2) Use the same generated code to implement the "is" keyword behind --harmony
flag.
3) Once the --harmony flag is gone, switch Object.is() to actually use the "is"
keyword.

+    return (obj1 !== 0) || (1 / obj1 === 1 / obj2);
+  } else {
+    return (obj1 !== obj1) && (obj2 !== obj2);
+  }
+}
+
+
 %SetCode($Object, function(x) {
   if (%_IsConstructCall()) {
     if (x == null) return this;
     return ToObject(x);
   } else {
     if (x == null) return { };
     return ToObject(x);
   }
 });
 
@@ skipping 19 matching lines @@
   ));
   InstallFunctions($Object, DONT_ENUM, $Array(
     "keys", ObjectKeys,
     "create", ObjectCreate,
     "defineProperty", ObjectDefineProperty,
     "defineProperties", ObjectDefineProperties,
     "freeze", ObjectFreeze,
     "getPrototypeOf", ObjectGetPrototypeOf,
     "getOwnPropertyDescriptor", ObjectGetOwnPropertyDescriptor,
     "getOwnPropertyNames", ObjectGetOwnPropertyNames,
+    "is", ObjectIs,
     "isExtensible", ObjectIsExtensible,
     "isFrozen", ObjectIsFrozen,
     "isSealed", ObjectIsSealed,
     "preventExtensions", ObjectPreventExtension,
     "seal", ObjectSeal
   ));
 }
 
 SetUpObject();
 
@@ skipping 144 matching lines @@
   if (IS_UNDEFINED(precision)) return ToString(%_ValueOf(this));
   var p = TO_INTEGER(precision);
   if (p < 1 || p > 21) {
     throw new $RangeError("toPrecision() argument must be between 1 and 21");
   }
   var x = ToNumber(this);
   return %NumberToPrecision(x, p);
 }
 
 
+// Harmony isFinite.
+function NumberIsFinite(number) {
+  return IS_NUMBER(number) && NUMBER_IS_FINITE(number);
+}
+
+
+// Harmony isNaN.
+function NumberIsNaN(number) {
+  return IS_NUMBER(number) && NUMBER_IS_NAN(number);
+}
+
+
 // ----------------------------------------------------------------------------
 
 function SetUpNumber() {
   %CheckIsBootstrapping();
   %OptimizeObjectForAddingMultipleProperties($Number.prototype, 8);
   // Set up the constructor property on the Number prototype object.
   %SetProperty($Number.prototype, "constructor", $Number, DONT_ENUM);
 
   %OptimizeObjectForAddingMultipleProperties($Number, 5);
   // ECMA-262 section 15.7.3.1.
@@ skipping 24 matching lines @@
 
   // Set up non-enumerable functions on the Number prototype object.
   InstallFunctions($Number.prototype, DONT_ENUM, $Array(
     "toString", NumberToString,
     "toLocaleString", NumberToLocaleString,
     "valueOf", NumberValueOf,
     "toFixed", NumberToFixed,
     "toExponential", NumberToExponential,
     "toPrecision", NumberToPrecision
   ));
+  InstallFunctions($Number, DONT_ENUM, $Array(
+    "isFinite", NumberIsFinite,
+    "isNaN", NumberIsNaN
+  ));
 }
 
 SetUpNumber();
 
 
 // ----------------------------------------------------------------------------
 // Function
 
 $Function.prototype.constructor = $Function;
 
@@ skipping 120 matching lines @@
 
 function SetUpFunction() {
   %CheckIsBootstrapping();
   InstallFunctions($Function.prototype, DONT_ENUM, $Array(
     "bind", FunctionBind,
     "toString", FunctionToString
   ));
 }
 
 SetUpFunction();