Various thoughts:

>> How much does the fact that a symbol *could* be used (in theory) matter in 
>> practice? Most regexes I see for valid identifiers are still of the 
>> ^[a-zA-Z_$][0-9a-zA-Z_$]*$ variety.
>> 
>> I’d expect λ to be in use in Greece, but how about ƒ (which has been 
>> mentioned many times)? It seems very appropriate and is even easy to type on 
>> a Mac (easier than square brackets on a German keyboard!).
> 
> It's hard to type λ on many keyboards. ƒ is easier, but neither is 
> backward-compatible:
> 
> js> ƒ = 1
> 1
> js> ƒ
> 1
> js> λ = 2
> 2
> js> λ
> 2
> 
> We rejected these already for these reasons.

My thinking was: If no one ever uses λ as an identifier (not likely in Greece) 
or ƒ as an identifier (likely, given that most people seem to think JS 
identifiers must adhere to the regexes shown above) then one would be free to 
make them reserved tokens in ES6. Counter arguments:

- Hard to type: reading is far more important than typing, it is very easy to 
adapt tools to help with typing.

- Not ASCII: I hardy every encounter non-UTF text files, any more. Non-ASCII 
seems to work well for Fortress.

> I think "use fn;" (real pragma syntax), with the low-precedence 
> assignment-expression fn (params) assign-expr production, wins. What do you 
> think?

Having fn would be sweet. For many kinds of pragmas, it would be great if one 
could configure these per project (or per directory). Then one could put legacy 
code in one directory and ES6 code in another. And the weight of the pragmas 
would be negligible. Not sure how to do this, though; reminds me very loosely 
of CSS (centralized management of style).

Would fn make sense as an ES6 breaking change? I’d expect many people to be 
strongly in favor, possibly as many strongly opposed.

Possible research (applies to ƒ, too):
- Poll people for their opinion
- Search JS code bases for how often the identifier "fn" is used (how?).

-- 
Dr. Axel Rauschmayer
[email protected]

home: rauschma.de
twitter: twitter.com/rauschma
blog: 2ality.com

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