arrow function syntax simplified

[Claus Reinke]

>> Your point about synthesizing dynamic-|this| given lexical-|this| forms 
>> is good. It seems to me having fn, rec, and => is therefore best. What 
>> am I missing?
> 
> That is my current state of thinking, too.

Until I started thinking about performance:-( With current 
implementations, at least, using rec is impractical: not just
slow but "too much" recursion. Which raises some questions:

- what is the state of play/plans wrt implementing tail-call 
    optimization?

- what are the chances of JS implementations optimizing
    the overhead of fn and rec away? Overheads include

    - call-by-value requires eta-expansion (wrapping the
        recursive term to avoid runaway evaluation)

    - preference of multi-parameter lists over nested single
        parameters leads to use of apply/slice/concat

It is sad to see a language design question decided by
implementation limitations, but until the questions above
receive good answers (or someone comes up with better
combinators;-), my proposed scheme is not practical.

Claus