Re: Operators on functions
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- Subject: Re: Operators on functions
- From: Pierre-Yves Gérardy <pygy79@...>
- Date: 2013年11月22日 12:11:20 +0100
On Fri, Nov 22, 2013 at 6:38 AM, H. Conrad Cunningham
<hcc@cs.olemiss.edu> wrote:
> On Tue, Nov 19, 2013 at 10:26 PM, Philipp Janda <siffiejoe@gmx.net> wrote:
> Also thanks. Weak tables were not in my "working set" of Lua programming
> features and techniques at the time (or yet for that matter).
Here's the gist for weak keys:
is_cell = setmetatable({}, {__mode="k"}) -- a table with weak keys
function cons(a,b)
local cell = {a,b} -- cell == table: 0x12345678
is_cell[cell] = true
return cell
end
c = cons(1,2)
is_cell[c] --> true
for k,v in pairs(is_cell) do print(k,v) end --> table: 0x12345678, true
c = nil
collectgarbage()
for k in pairs(is_cell) do print(k) end --> nothing
The presence of the key in the weak table does not prevent it from
being garbage collected. There's a chapter in PiL that covers it in
more in depth.
-- Pierre-Yves