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On Wed, Jun 4, 2014 at 11:31 PM, Roberto Ierusalimschy <> wrote:
> I THINK (and I'm not certain) that differing line numbers in the debug
> info is enough to mark them as "different". I think "similar enough"
> essentially refers to two functions being instantiated by different
> iterations of the same line of code.


Okay. This is (pretty much) the whole constructor:

local function url(url_str)
local self
if type(url_str) == "string" then
self = url_pat:match(url_str)
elseif type(url_str) == "table" and url_str.url then
return url(url_str.url)

if self then
self.socket = .. 
(self.port and (":"..("%d"):format(self.port)) or "")
self[0] = self.socket
self.xpath = xpath:match(url_str)
self.url = "" .. "://" .. self.xpath
self.route = route
return setmetatable({}, {
--for brevity, I'm only including the function in question.
__eq = function(a, b) return a.url == b.url end ,



This would seem to support "similar enough". 

If I run tests in the same file as this code, it never fails to see the functions as the same. 

--complete module definition is above this comment...

for i = 1, 10001 do
local a = url("mcp://host/thread/name/"..tostring(i))
local b =  url("mcp://host/thread/name/"..tostring(i) .."/")
assert(a == b)
-->  passed!

If I run them in a different file (require the module), it _often_ does. That is, it's not only within Lua Busted.

If I run the garbage collector between assignments, it will fail every time. 

local url = "">

local a = url("mcp://host/thread/name")
local b = url("mcp://host/thread/name/")
print(a == b)
--> false
print(getmetatable(a).__eq, getmetatable(b).__eq)
--> function: 00000000004337D0 function: 00000000003E9550

Is this expected? Can you provide some insight as to how I can understand this better?