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2011/5/2 Lorenzo Donati <>:
> I know that I could either:
> 1) generate an unique ID with a custom algorithm
> 2) upon creation, before attaching the metatable to the object being
> created, call tostring on the object and store the ID in a (weak?) table.
> 3) use a proxy and return the ID of the "private" object instead (preserves
> uniqueness because of the 1-to-1 relationship between proxies and objects)

You can modify 1) a bit to make it less performance critical:

local idcnt = 0
local idcache = setmetatable({},{__mode='k',__index = function(t,k)
idcnt = idcnt + 1 t[k] = idcnt return idcnt end})
function getid (o) return idcache[o] end

So this would only affect performance for debug code that tags objects
if you take a look at them.

Aside from this, I don't know any other trick. Well, you could also
erase the metatable, get the string and restore the original metatable

And besides all that: You could look into the Lua code and find out,
how the table:#xxx code looks like and provide it as additional
function if you have access on the C API. E.g. table.getpointerid