Re: Basic question on weak keys

[TNHarris <telliamed@...>]

On Wednesday, June 13, 2012 05:59:54 PM Andrew Starks wrote:
> 
> Why nil? I thought that since a[b] was not weak, it would keep it as a
> reference? What does __mode ="k" do if an object is collected  when it
> is used in a table as a key? Can someone be so kind as to provide an
> example?
> 

As has been mentioned, you are not testing what you think you're testing. 
Consider this instead.

    a = {}
    b = {}
    a[b] = "foo"
    for k,v in pairs(a) do print(k,v) end
    --> table: 0x18066a0        foo
    b = nil
    collectgarbage('collect')
    for k,v in pairs(a) do print(k,v) end
    --> table: 0x18066a0        foo

In contrast, 

    a = setmetatable({}, {__mode="k"})
    b = {}
    a[b] = "foo"
    for k,v in pairs(a) do print(k,v) end
    --> table: 0xd9f8b0         foo
    b = nil
    collectgarbage('collect')
    for k,v in pairs(a) do print(k,v) end
    --> 


-----
-- tom
telliamed@whoopdedo.org