On Tue, Feb 21, 2012 at 1:56 PM, Axel Kittenberger
<axkibe@gmail.com> wrote:
This needs Lua 5.2, with 5.1 or LuaJIT you're mostly out of luck (as
far I know). Also note this will make a copy of original at the moment
of write, not of the moment made the COW, so if you change the
original before, it changes in background. But I suppose you consider
that one immutable.
function makeCOW(o)
return setmetatable({}, {
__index= o,
__pairs = function() return pairs(o) end,
__ipairs = function() return ipairs(o) end,
__newindex =
function(t, k, v)
setmetatable(t, nil)
for ck, cv in pairs(o) do t[ck] = cv end
t[k] = v
end,
})
end
local org = {1,2,3,4,5,6,7,8,9}
local cpy = makeCOW(org);
for k, v in ipairs(cpy) do print(k, v) end
print('----')
cpy[2] = 5
for k, v in ipairs(cpy) do print(k, v) end
