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- Subject: Re: Recipe: setfenv with Lua 5.2.0 work3
- From: Roberto Ierusalimschy <roberto@...>
- Date: Thu, 20 May 2010 13:15:37 -0300
> With Lua 5.1, I have the following code :
> setfenv(level, M)
> With Lua 5.2.0 work2, I rewrite it as following (compatible with Lua 5.1) :
> debug.setfenv(debug.getinfo(level, 'f').func, M)
> Now, with Lua 5.2.0 work3, it becomes :
> if debug.setupvalue(debug.getinfo(level, 'f').func, 1, M) ~= '_ENV' then
> setfenv(level, M) -- Lua 5.1
> The value 1 seems magical, but I think _ENV is alway the first upvalue.
Not necessarily. If the function is a main function (that is, the direct
result of load) then _ENV is always the first (and only) upvalue and it
is always present. Other functions have _ENV just like any other upvalue.
For instance, consider the following code:
function foo ()
return a + b
In function foo, the first upvalue is 'a' and the second is '_ENV'.