Re: [ANN] Lua 5.2.0 (alpha-rc2) now available

[Pierre-Yves Gérardy <pygy79@...>]

On Friday, November 19, 2010, Petite Abeille <petite_abeille@mac.com> wrote:
> On Nov 19, 2010, at 11:08 PM, Luiz Henrique de Figueiredo wrote:
>> can now write
>>       ; (exp)...
> Ah, excellent, thanks!

Definitely :-). The only feature in my whishlist still missin in 5.2
is short lambdas.

Functions are first class citizens semantics-wise, but not
syntax-wise, when compared to strings or table IMO.

At a glance, function calls and anonymous function declarations are
too similar, making lambda-rich code harder to read than it should be.

I would love to have the ability to pass functions without parentheses
like you can do with string and table literals. Finding an appropriate
candidate (simple, short and unambiguous yet not too ugly) is not
easy, though. I've submitted such a patch a while ago and have messed
with a lot of variations sonce then, but I couldn't find an obvious
candidate.

My main considerations are:

a) the token opening the block
b) the argument list
c) the return token
d) the token closing the block

The easy stuff first: the return token could be "|" as in the current
power patch, or "=>", which is more meaningful but longer.

I like "@" as an initial token because it is distinctive. far more
than a potential "fn" keyword, for example. :(, :[ or :] could also be
used, but it would overload the meaning of existing symbols.

The argument list doesn't need delimiters except when there are no arguments.

    @[ a,b => a+b ] would work, but how would one represent an empty list?

Perhaps by using the empty statement?

    function make_counter()
        local a = 0
        return @[; a=a+1; => a ]
    end

If we chose to have an argument list delimiter, Do we balance the
block opening token

    @[a,b| =>a+b ] -- use a pipe

    @[a,b; => a+b ] -- make an empty statement mandatory at the
beginning of the block?

    @ a, b [=> a+b]

    @[a,b] => a+b ]

    @[a,b] => a+b end


Regarding the code modifications, it is a bit more complicated to
restrict the short return statement to the short functions, but I
think it would be better to confine it there.

My favourite syntax so far is

    @[ a,b => a+b ]

and

    @[; dostuff() ]

I would love to hear the opinion of Roberto and Luiz on this topic.

Kind regards,
-- Pierre-Yves