Re: [manual] the table library and metatables
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- Subject: Re: [manual] the table library and metatables
- From: Dirk Laurie <dirk.laurie@...>
- Date: 2016年1月27日 20:45:07 +0200
2016年01月27日 19:09 GMT+02:00 Stephan Hennig <sh-list@posteo.net>:
> A test shows that none of these functions, that
> I'd consider part of "the table library", respect a table's __index
> metamethod.
>
> -- A table with three entries.
> local t = { 1, 2, 3 }
> -- We add a fourth one that is accessible via
> -- the __index metamethod.
> local mt = {
> __index = { [4] = 4 },
> }
> setmetatable(t, mt)
They do respect the __index metamethod, but the primitive
length calculation does not. Since you have failed to provide
__len, #t is still 3. The documentation
> mt.__index = function() return 4 end
> table.concat(t)
1234
The manual does state clearly that "the table must be a proper sequence
or have a __len metamethod ". That's enough.