Re: upcoming changes in Lua 5.2 [was Re: Location of a package]

[Roberto Ierusalimschy <roberto@...>]

> I'm upset to find that adding 'continue' is not even being considered.
> (Just to let you know that there still are ones that miss it).

Here is a fine example of hiden costs of features.

In Lua 5.1, we changed the scope rules for repeat-until, so that the
test is included in the scope of the body. That seemed a nice and
innocent feature, allowing code like this:

  repeat
    ...
    local x = ...
    ...
  until something-with-x

Of course this change would cause no harm...

Now, consider the addition of 'continue':

  repeat
    ...
    if something then continue end
    ...
    local x = ...
    ...
  until something-with-x

We have two options: either the continue jumps into the scope of 'x'
bypassing its declaration/initialization (very bad), or the continue
skips the test altogether (very bad too).

So, it seems that continue is incompatible with this scope rule...

-- Roberto