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- Subject: Re: finding out number of records in a table??
- From: Luis Carvalho <carvalho@...>
- Date: Tue, 12 Sep 2006 15:17:57 -0400
> That is, I'm sorry, but I fail to see why one might need a __removeindex
> metamethod. OTOH, being able to set a __len metamethod for tables would be
> useful (along with a "rawlen" function for tables, probably).
Correcting myself: the proxy was needed because of __len _and_ __newindex. It
would also be nice to have for table's newindex to look for a __newindex
metamethod. Now I understand the need for a __removeindex, but it would be
better to see nil assignments (to existing keys) treated by __newindex for
tables in the same way as for other objects -- although there should be a good
reason for why this is so. :)
Another last minute update:
local newproxy = newproxy
local getmetatable = getmetatable
local next = next
mt.__index = function(o,k) return t[k] end
mt.__newindex = function(o,k,v)
if k~=nil then
if t[k]==nil and v~=nil then -- new key?
elseif t[k]~=nil and v==nil then -- remove key?
mt.__len = function(o) return n end
mt.__hash = t
return next, getmetatable(h).__hash, nil
Luis, needs to think more before posting. :)
A mathematician is a device for turning coffee into theorems.
-- P. Erdos
Applied Math PhD Student - Brown University
PGP Key: E820854A <firstname.lastname@example.org>