Re: __pairs metamethod - is it in?
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- Subject: Re: __pairs metamethod - is it in?
- From: Mark Hamburg <mhamburg@...>
- Date: 2005年2月07日 08:16:20 -0800
Because next isn't just an implementation detail at this point. It's a
global function and if one wants to override pairs, one might want to
override next. Given that, it would be nice if the override logic for pairs
would recognize a __next override so that programmers wouldn't have to
override both and so that a table iteration with an overridden next wouldn't
do more metatable lookups than necessary.
The simpler proposal would work if next were removed from the standard API
though I might then want an equivalently lightweight way to test for an
empty table.
Mark
on 2/7/05 2:32 AM, Asko Kauppi at asko.kauppi@sci.fi wrote:
>
> Why so complicated?
>
> I must be missing something, since isn't 'next()' just an
> implementation detail of 'pairs' and 'ipairs'. I mean, if I want to
> redefine those to actually support '__[i]pairs' metamethods, wouldn't
> this be sufficient:
>
> pairs = function( t )
> local mt = getmetatable( t )
> return ( ( mt and mt.__pairs ) or raw_pairs )( t )
> end
>
> ipairs = function( t )
> local mt = getmetatable( t )
> return ( ( mt and mt.__ipairs ) or raw_ipairs )( t )
> end