Existential operator (was: ||= is much needed?)

[Brendan Eich]

Brendan Eich wrote:
> Worse, instead of leaking an observable ConditionalReference (whew!), 
> you've opted to break the equivalence between foo.bar() and %tmp = 
> foo.bar; %tmp.call(foo) for the case where . is replaced by ?. -- in 
> this case your proposal does not throw while the expansion does.
>
> The right extension for what CoffeeScript calls ?( is simply to use an 
> unambiguous and backward-compatible extension, such as ?.( instead. 

Jeremy pointed out privately that the need for ?( is less acute in 
practice, and also because of .call via the equivalences:

   foo.bar?(args) <==>  foo.bar?.call(foo, args)
   fun?(args) <==>  fun?.call(undefined, args)

But ?.( is shorter. It's awkward to use three chars instead of 
CoffeeScript's two, and to have a dot in the middle where no get or set 
is implied.

/be