Re: Size of a non numerical indexed table

[Rici Lake <lua@...>]

On 1-Sep-05, at 11:19 AM, Mark Hamburg wrote:

> I've been contemplating whether Lua needs:
>
>     function argforeach( fn, ... )
>         for I = 1, select( "#", ... ) do
>             fn( ( select( I, ... ) ) )
>         end
>     end
>
> This should be written in C to avoid the performance issues cited 
> above and
> probably needs a better name.

A simpler and possibly more general one would be:

  for i, v in eachi(<list of values>) do

which you could call:

  for i, v in eachi(...) do

but it does require copying the ... several times.

As an aside, this is one of the (several) reasons I personally would 
have prefered built-in tuples, with the varargs syntax creating a tuple 
instead of a table. While this is not as fast as the magic ... solution 
in some simple use cases, the additional power makes it considerably 
faster in a variety of other use cases, including iterating over 
parameter lists, and it is considerably faster than varargs creating a 
table. (Tuples also allow a neat way of capturing multiple return 
values, and a way of using varargs as an upvalue.)

> An alternative would be to extend the syntax to define:
>
>     for i, v in ... Do
>         -- do stuff with the i-th element of ...
>     end
>
> So that it implements the appropriate loop. This means that if you 
> want to
> pass iteration parameters via ..., then you will need to bind them to 
> locals
> outside of the loop or use select( 1, ... ) in the loop.

ick. Sorry. More magic to the magic ...

> P.S. The absence of standard support for packing and unpacking argument
> lists containing nil is an annoyance.

Agreed. (cough, cough, tuples would solve that issue too)