Re: es5 bug, operator == and valueOf

[Peter van der Zee]

Has an operator like == ever been proposed? So the strict relational
operator that returns NaN if typeof left and right don't match.
If so, why was it shot down? Bloat? Relatively useless?

- peter

On Wed, Dec 1, 2010 at 1:45 AM, Brendan Eich bren...@mozilla.com wrote:

 On Nov 30, 2010, at 3:25 PM, Fyodorov Bga Alexander wrote:

  @apipkin have found logic bug
  `{valueOf: function(){ return 1 }} == {valueOf: function(){ return 1 }}`
  // false
  `{valueOf: function(){ return 1 }} = {valueOf: function(){ return 1 }}`
  // true, ok

 This is not a bug in ES5, although you could argue it's a design flaw in
 JS. Recall that

 typeof a == typeof b  a == b = a === b  // implies, in both directions

 Two object initialisers never evaluate to the same object reference, and
 === compares references, and == here has same-typed (object) operands, so it
 is the same as ===.

 Relational operators do convert objects. You could argue this is a design
 flaw; or that this is a win but then == should convert objects as well --
 but if that is a flaw, it's only in hindsight, since === came after == and
 without === there would be no way to distinguish object references without
 implicit conversion.

 Really, implicit conversions (not the same as operator methods) are a
 design flaw in my view. They make == (ignoring NaN) not an equivalence
 relation.

 But again, not an ES5 bug. Did you read ES1-3 on == and valueOf
 differently?

 /be

 ___
 es-discuss mailing list
 es-discuss@mozilla.org
 https://mail.mozilla.org/listinfo/es-discuss

___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss

Re: es5 bug, operator == and valueOf

[Jason Orendorff]

On Wed, Dec 1, 2010 at 2:45 AM, Peter van der Zee e...@qfox.nl wrote:
 Has an operator like == ever been proposed? So the strict relational
 operator that returns NaN if typeof left and right don't match.
 If so, why was it shot down? Bloat? Relatively useless?

Well,  is used more often than =. How would you spell strict ?

I think when people use , =, etc. they almost always suppose
(correctly or incorrectly) that the operands are sure to be both
numbers (or both strings). If they aren't, the programmer's
assumptions have already been violated; the code will likely misbehave
whatever answer the language gives. That is, even if the language
provided strict comparisons, and people used them, it probably
wouldn't help. This stands in contrast to code like `if (x ==
undefined)` where there may be no presupposition at all about what
sort of value x is.

-j
___
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss