for loops

[lhf (Luiz Henrique de Figueiredo)]

We'd like your opinion on whether we should add a FOR loop to Lua:

1. Do you miss FOR loops?
2. What syntax would you suggest?

We have been dicussing the matter and have decided that if we're going to add
FOR loops to Lua then it must be a general kind of FOR (as in C), not just the
numeric type (as in FORTRAN, Pascal or Basic).
In other words, we should be able to traverse a table or a linked list using
a FOR.

Now, the real problem is syntax.
After some heated discussion, we think that the syntax below is ok:

   FOR statement1 THEN statement2 WHILE expression DO block END

which is sugar for

   statement1
   WHILE expression DO block; statement2 END

With this FOR you can write:

   for i=1 then i=i+1 while i<=10 do s=s+a[i] end

and also

   for local i,v=next(t,nil) then i,v=next(t,i) while i do process(i,v) end

and also

   for local x=head then x=x.next while x do process(x) end

However, we're not really too happy with this, nor really convinced that Lua
needs a FOR loop.

We'd like your input on this matter.
Thanks.
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Luiz Henrique de Figueiredo                    email: lhf@tecgraf.puc-rio.br
TeCGraf-Grupo de Tecnologia em Computacao Grafica, Dep. Informatica, PUC-Rio
Rua Marques de Sao Vicente 225                        voice: +55 21 529-9424
22453-900 Rio de Janeiro, RJ, Brasil                    fax: +55 21 294-8195
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