Re: get_local() and "(for index/limit/stop)"

[Fabio Mascarenhas <fabiomasc@...>]

Rici Lake wrote:
> The real index name is the last localvar; it is not in scope until the loop
> starts. Consequently, for loops correctly (imho) create a new index object
> on each loop, which in turn means that upvalues work correctly.
>
> In other words:
>
>   timestable = {}
>   for i = 1, 10 do
>     timestable[i] = function(j) return i * j end
>   end
>
> will do the right thing in lua 5.1, and something quite different
> in earlier versions.

Depends on how you interpret the for loop. If you interpret the loop as:

do
  local i = 1
  repeat
    timestable[i] = function(j) return i * j end
    i = i + 1
  until i > 10
end

Then the right thing is the behavior of Lua 5.0.2 (in fact, this is the 
way for is explained in the reference manual :-) ). You can easily have 
it the other way by explicitely declaring another local:

timestable = {}
for i = 1, 10 do
  local k = i
  timestable[i] = function(j) return k * j end
end

The new way just makes it more convenient. Well, I'm sure this new way 
will be documented in the 5.1 reference manual. :-) And the loop 
variable is not really created anew each iteration; the same register is 
reused. There is no performance penalty.

--
Fabio Mascarenhas