Expose SameValue equality comparison algorithm

src/objects.cc

 // 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 987 matching lines @@
 
 
 bool Object::SameValue(Object* other) {
   if (other == this) return true;
 
   // The object is either a number, a name, an odd-ball,
   // a real JS object, or a Harmony proxy.
   if (IsNumber() && other->IsNumber()) {
     double this_value = Number();
     double other_value = other->Number();
-    return (this_value == other_value) ||
-        (std::isnan(this_value) && std::isnan(other_value));
+    bool equal = this_value == other_value;
+    // SameValue(NaN, NaN) is true.
+    if (!equal) return std::isnan(this_value) && std::isnan(other_value);
+    // SameValue(0.0, -0.0) is false.
+    return (this_value != 0) || ((1 / this_value) == (1 / other_value));

[yusukesuzuki, 2013/09/24 12:58:26]

According to the comment of Object::SameValue in objects.h, this method
represents ECMA262 SameValue and Harmony egal operator.
So `SameValue(0.0, -0.0)` should return false.

   }
   if (IsString() && other->IsString()) {
     return String::cast(this)->Equals(String::cast(other));
   }
   return false;
 }
 
 
 void Object::ShortPrint(FILE* out) {
   HeapStringAllocator allocator;
@@ skipping 15082 matching lines @@
 #define ERROR_MESSAGES_TEXTS(C, T) T,
   static const char* error_messages_[] = {
       ERROR_MESSAGES_LIST(ERROR_MESSAGES_TEXTS)
   };
 #undef ERROR_MESSAGES_TEXTS
   return error_messages_[reason];
 }
 
 
 } }  // namespace v8::internal