delegating to typed objects

P T Withington ptw at pobox.com
Mon Jul 9 16:32:49 PDT 2007


On 2007-07-09, at 19:16 EDT, Brendan Eich wrote:

> Having thought about 1 more, I'd like to point out that it's *not*  
> what ES3 does:
>
> js> function F(){}
> js> F.prototype = d = new Date
> js> f = new F
> js> f.__proto__ === d
> true
> js> f.setTime(0)
> typein:10: TypeError: Date.prototype.setTime called on incompatible  
> Object
>
> So new F did create an Object instance, and it linked its __proto__  
> (ES1-3 [[Prototype]] internal property) to d. Not what Kris  
> proposes by analogy to ES1-3, so I'm favoring 2 at the moment.

[Coming late to the party]

And it has burned me that I could not do that.  I wanted to write an  
'annotated string' and couldn't because of exactly this restriction.   
Will I be able to subclass built-in types?  Or will their methods be  
hard-wired in some way that raises similar issues?





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