Re: tostring tag method proposal

[Ignacio Castaño <castanyo@...>]

hey, that's cool!
thanks for the code ;-)

Ignacio Castaño
castano@asidesoft.com


Aaron Kamienski wrote:
> You can do this simply by replacing the tostring function.
> To simplify it even further, also replace the settagmethod
> and gettagmethod functions.  Here is some code that I've
> been using to add arbitrary tag methods (e.g., tostring,
> type, and next).
>
> It works with userdata just fine (I ran into the same
> problem which is why I did it -- although it was originally
> for lua3.2).  The next tag method (along with a foreach
> replacement) gave me the ability to traverse my C structures.
>
> Hope it helps,
>
> ajk
>
> ---- tagmethods.lua ----
> _tagmethods =

> -- next = _nextmethods,
> -- tostring = _tostringmethods,
> -- type = _typemethods
> }
>
> _settagmethod = settagmethod
> function settagmethod (tag, method, f)
> local tm = _tagmethods[method]
> if tm then
> tm[tag] = f
> else
> %settagmethod(tag, method, f)
> end
> end
>
> function validtagmethods (new_only)
> local t
> if new_only and new_only ~= 0 then
> t = {}
> else
> t = { "add", "sub", "mul", "div", "pow", "unm",
> "lt", "gt", "le", "ge",
> "concat", "index",
> "getglobal", "setglobal", "gettable", "settable",
> "function", "gc"
> }
> end
> if new_only ~= 0 then
> local i = next(_tagmethods, nil)
> while i do
> tinsert(t, i)
> i = next(_tagmethods, i)
> end
> end
> return t
> end
>
> _gettagmethod = gettagmethod
> function gettagmethod (tag, method)
> local tm = _tagmethods[method]
> if tm then
> return tm[tag]
> else
> return %gettagmethod(tag, method)
> end
> end
>
> ---- tostring.lua ----
> _tostringmethods = {}
> _tostring = tostring
> function tostring (obj)
> local method = _tostringmethods[tag(obj)]
> if method then
> return method(obj)
> else
> return %tostring(obj)
> end
> end
>
> _tagmethods.tostring = _tostringmethods
>
> --
> Aaron Kamienski <aaronk@snaptwo.com>
> SNAP2 Corporation


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