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> I would be happy to see refs go away because they seem like a sharp,
> tempting feature that actually doesn't add value.
> If your userdata object needs to reference other Lua data, you
> really, really, really want to use the environment mechanism because
> this works with the GC whereas refs are very prone to creating
> uncollectable cycles.
> If your C code needs to reference a Lua value, I tend to recommend
> using light userdata keys in the registry bearing in mind that this
> creates anchors for the GC.

Exactly. The archetypal use of references were a full userdata keeping
references to other Lua values by keeping in its C structure the
integers returned by luaL_ref. The finalizer for this userdata should be
responsible to release its references when the userdata was collected.
This kind of use became obsolete with environments.

Does anyone still use references in real applications? For what?

-- Roberto