Re: changing global environments

On Mar 26, 2007, at 2:33 AM, Asko Kauppi wrote:

I'm surprised this is an issue - my knowledge of the environments is not complete, and I had always thought subfunctions would be effected. In other words, that it is easy to make a "jail" in Lua.

Lua Lanes would give you one solution, since it allows defining which standard libraries a given lane (OS thread + Lua state) are initialized with. In addition, you'd gain speed when run on multicore processors.

Usage:

require "lanes"

local lane= lanes.prepare( fsub )( ...parameters... )
...

print( lane[1] ) -- return values

Interested?

To give the substate some standard libs, one can:
lanes.prepare( fsub, "os+math" )
lanes.prepare( fsub, "*" )

Graham Wakefield kirjoitti 25.3.2007 kello 1:09:

Well I wouldn't propose it as the default behaviour at all, but it would be nice to be able to create 'environment-less' functions in addition to Lua's functions with bound environments.

I didn't know about debug.sethook, but looking at it now, it seems that it would affect ALL function calls (and I suppose will be expensive too).

perhaps a wrapper function:

function envwrap(f)
setfenv(f, getfenv(1))
return f()
end

or more correctly

function envwrap(f)
local e = getfenv(f)
setfenv(f, getfenv(1))
args = {f()}
setfenv(f, e)
return unpack(args)
end

and in use:

fsub = function()
print("fsub", getfenv(0), getfenv(1))
b = 1
end

fmain = function()
print("fmain", getfenv(0), getfenv(1))
a = 1
envwrap(fsub())
end

But I feel like I'm doing a lot of expensive workaround, where a simpler 'environment-less' function would suffice.

On Mar 24, 2007, at 4:00 PM, Tomas Guisasola Gorham wrote:

Hi Graham

Is there any way to set the environment of a function such that all
functions it calls will also inherit this environment? In the
example below, I change the environment of fmain, which in turn calls
fsub, but the environment of fsub is unchanged.

I don't think so. Anyway I think it should became a nightmare
if this became the default behavior. Good luck!
By the way, did you try to set the call hook to do that change
of environments?

Again, good luck,
Tomás

Grrr Waaa
www.grahamwakefield.net