Re: [ANN] Lua 5.2.0 (work1) now available
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- Subject: Re: [ANN] Lua 5.2.0 (work1) now available
- From: Patrick Donnelly <batrick@...>
- Date: 2010年1月10日 23:12:52 -0500
On Sun, Jan 10, 2010 at 10:01 PM, Tom N Harris <telliamed@whoopdedo.org> wrote:
> Nevin Flanagan wrote:
>>
>> On Jan 9, 2010, at 3:26 PM, Tom N Harris wrote:
>>> __index can be a table instead of a function. Can __len be a number?
>>
>> It seems to me that it could be, if it can't be now. That seems to fit well into the Lua idiom.
>
> The manual is misleading about __len. The pseudo-code says...
>
> function len_event (op)
> --[[ snip ]]--
> local h = metatable(op).__len
> if h then
> return (h(op)) -- call handler with the operand
> elseif type(op) == "table" then
> return #op -- primitive table length
> --[[ snip ]]--
>
> If that were the case, then this would be possible...
>
> T=setmetatable({},{
> __len=setmetatable({gth=0},{
> __len=function(o) return o.gth end
> })
> })
> getmetatable(T).__len.gth = 3
> print(#T)
I don't see any error in the implementation here. Try this:
> do
T=setmetatable({},{
__len=setmetatable({gth=0},{
__call=function(o) return o.gth end
})
})
getmetatable(T).__len.gth = 3
print(#T)
end
3
?
> An unrelated minor bug in 5.2 (actually 5.1 has it too):
>
> S=[[]]
> T={}
> C=coroutine.create(function() end)
> print(type(S),type(T),type(C))
> print(S<T)
> print(T<T)
> print(S<C) -- error message is wrong
I get this bad error message too.
--
-Patrick Donnelly
"Let all men know thee, but no man know thee thoroughly: Men freely
ford that see the shallows."
- Benjamin Franklin
- References:
- [ANN] Lua 5.2.0 (work1) now available, Luiz Henrique de Figueiredo
- Re: [ANN] Lua 5.2.0 (work1) now available, Alexander Gladysh
- Re: [ANN] Lua 5.2.0 (work1) now available, Alexander Gladysh
- Re: [ANN] Lua 5.2.0 (work1) now available, Ignacio Burgueño
- Re: [ANN] Lua 5.2.0 (work1) now available, steve donovan
- Re: [ANN] Lua 5.2.0 (work1) now available, Alexander Gladysh
- Re: [ANN] Lua 5.2.0 (work1) now available, steve donovan
- Re: [ANN] Lua 5.2.0 (work1) now available, Tom N Harris
- Re: [ANN] Lua 5.2.0 (work1) now available, Nevin Flanagan
- Re: [ANN] Lua 5.2.0 (work1) now available, Tom N Harris