Re: table iteration problem
[
Date Prev][
Date Next][
Thread Prev][
Thread Next]
[
Date Index]
[
Thread Index]
- Subject: Re: table iteration problem
- From: Dirk Laurie <dirk.laurie@...>
- Date: 2011年10月18日 15:34:38 +0200
2011年10月18日 Victor Young <littlehaker@gmail.com>:
> It seems to be a simple and flexible method, thank you and Enrico
I append another solution to this solved problem :-)
Dirk
-- history.lua
-- Usage: history = require "history"
-- the function call 'history()' returns an empty table such that
-- 'pairs' preserves historical order of items added to it
-- Restrictions:
-- don't use the key '__keys'
-- Bugs masquerading as features:
-- the historical position of a key is remembered even if nil is
-- assigned as its value
-- if another assignment to a deleted key is made, the key appears
-- at both places in the history (but with the same value)
-- Dirk Laurie 2011年10月18日
-- LICENCE: Public domain
local function history()
local t = {__keys={}}
setmetatable (t,{
__newindex = function(self,index,value)
local keys = self.__keys
keys[#keys+1]=index
rawset(self,index,value)
end;
__pairs = function(self)
local i=0
return function()
i=i+1
local k=self.__keys[i]
return k, rawget(self,k)
end
end})
return t
end
--[[ Example
-- Add another hyphen to previous line to run the example
t = history()
t.a = 'A'
t.z = 'Z'
t[1] = '1'
t[3] = '3'
t[2] = '2'
for k,v in pairs(t) do print(k,v) end
--]]
return history