Lua 5.4 Tuples FTW!

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Re: __ipairs

Soni "They/Them" L.


On 2018-03-16 11:17 AM, Hisham wrote:

> On 16 March 2018 at 07:56, John Hind <[hidden email]> wrote:
>>>>>>> for i,v in pairs(t) do print(i,v) end
>>>>> A perfect example of why deprecating __ipairs was the wrong move. It
>>>>> ought to be possible to make this code work with ipairs(t) as well, but
>>>>> with no __ipairs metamethod it can't be done.
>>>>> Andrew.
>> Except of course by the simple expedient of replacing ipairs(t) with a
>> version
>> that does what you want it to do directly! Even, if you insist, with a
>> version that
>> uses a metamethod __ipairs! The metamethods on both pairs and ipairs have
>> always baffled me with their utter triviality!
> When writing a library, you cannot assume you can monkey-patch other
> people's standard libraries at will.
>
> Not everyone writes Lua code in a situation where they can play God
> with the environment.
>
> -- Hisham
>

Useful snippet to have in your code:

do local mt = {__ipairs=function(t) return t.i end} local t =
setmetatable({i=function() end},mt) if ipairs(t) ~= t.i then local
oldipairs = ipairs; ipairs = --[[monkeypatch here]] end end

Always probe the "standard" libraries, and always fallback to the
previous one. Never assume they haven't been monkeypatched. (Also,
probing helps with performance.)

--
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