On Jul 19, 2011, at 12:17 PM, Allen Wirfs-Brock wrote:

> On Jul 19, 2011, at 11:56 AM, Luke Hoban wrote:
> 
>>>> Object.extend(src, dest)
>> 
>>> This is certainly closest to paving the cowpath. Either via a built-in 
>>> module exporting 'extend', or as you suggest, directly on Object. The 
>>> Object.extend route is a bit harder to analyze, but not fatally so for any 
>>> capable static analysis framework.
>>> Either way (built-in module or Object.extend), old script (Hi Luke! ;-) 
>>> could use it too.
>> 
>> Agreed - this was my initial reaction to <| as well, and I still see a 
>> number of reasons to prefer a library solution over a syntax solution for 
>> both 'Obect.extend' and 'Object.make'.
>> 
>> The arguments for <| as an operator seemed to boil down to:
>> 1) It's more 'declarative'
>> 2) It can be optimized by engines
> 
> One issue is that <| conceptually modifies the [[Prototype]] of its RHS.  As 
> an operator (whether special character or keyword based) we can restrict the 
> RHS to be a literal and define the behavior such that no actual mutation of 
> [[Prototype]] is necessary.

Good point, and I should have noted that in my reply (which was supportive of 
Object.extend, where the problem does not arise).


> However, at the value level we have no way to distinguish an object that was 
> created via a literal and which has no references other than the current 
> argument value.  So, when we specify Object.make we have to accept an 
> arbitrary object as the second argument  and specify either [[Prototype]] 
> mutation or some sort of shallow copy, either of which can be problematic. 

We are *not* gonna standardize mutable [[Prototype]].

/be
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