Re: new "empty" value/type in Lua?
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- Subject: Re: new "empty" value/type in Lua?
- From: Dirk Laurie <dirk.laurie@...>
- Date: 2013年6月28日 08:37:21 +0200
2013年6月28日 Tim Hill <drtimhill@gmail.com>:
> I'm going to get shot for suggesting this… (hides under bed)
No, you won't. We've all been through this phase and survived it.
> I think there IS a case to be made for being able to store
> a value in a Lua array that is uniquely NOT any other Lua value.
> Essentially, I think that value is "empty"; a valid Lua value
> that is simply not the same as any other Lua value (including nil).
>
> Basically, empty would act like nil in most regards, except:
> -- Storing empty in a table element actually stores the value,
> rather than deletes it.
> -- When used in a boolean context, the empty value evaluates
> to true (unlike nil).
> -- Has a type() of "empty"
Would `empty` be allowed as a table key?
> -- Judging by the mail list chatter, a lot of Lua beginners
> struggle with the problem of nil in sequences.
It would be so much nicer to have them struggle with `empty`
instead.
> But, let's face it; they ARE all workarounds.
Those workarounds are not workarounds, they are special-purpose
solutions to special-purpose problems.
Here's another "workaround":
NaN = 0/0
It's different from all Lua values, including `nil` _and itself_.
It occupies a TValue, but is not a valid table key.
The proposed `empty` is likewise a mere workaround. Another
special-purpose solution to another special-purpose problem.