Optional brackets around lambda expression

[Bob Foster]

Maurizio Cimadamore wrote:
> On 17/06/11 07:59, Reinier Zwitserloot wrote:
>> Er, right. This redmond variant syntax of Ali Ebrahimi:
>>
>>
>> a, b, c ->  expression
>>
>> cannot work, as far as I can tell, in the current parser architecture of
>> javac and ecj, and attempting to work around it or fix the parser is a
>> massive undertaking. I think - experts, please chime in!
>>
> This is right - you can remove the parenthesis around the args when
> there is just one argument (and there is no explicit type on the lambda
> parameter); in that case the grammar would be something like:
>
> IDENTIFIER '->' ...
>
> In all other cases you need enclosing parens, as in:
>
> (a,b,c) -> body
> (Type1 a, Type2 b)-> body
>
> [the above can be disambiguated from a cast or a parenthesized
> expression because of the trailing ')->' sequence, which would be unique
> to lambdas].
>
> Another alternative, for those who don't like surrounding parenthesis,
> would be to use a special prefix (as in SoTL or Strawman), as in:
>
> #a,b,c->body

I'm not going to pretend to be a parsing expert, particularly if it's
defined in terms of the changes can be easily made to the the javac parser,
but...

This would be no problem for a PEG. Isn't the whole idea that you can't look
ahead a bit somewhat outmoded?

Bob