220 2433 <CAOHCbitWGAFHwVMNQA4T4QEXG0c4oKrvFo2bcMkyi1y=nViXkg@mail.gmail.com> article
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From: Tony V E <tvaneerd@gmail.com>
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Subject: Re: optional<T>, one more value or two states
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On Fri, Jan 25, 2013 at 6:22 PM, Nicol Bolas <jmckesson@gmail.com> wrote:
>>
>> Is there a difference between empty and null?
>
>
> Yes: `optional<T*>` exists. Such an object has 3 possible states: the
> optional could be empty. The optional could contain a valid pointer. Or the
> optional could contain nullptr.
>
> That's why we should not consider them the same. To me, "null" means "a
> pointer which has no value and cannot be derefenced". If you say that an
> `optional<T*>` is "null", my assumption is that you're talking about what is
> stored within the optional and not the state of the optional itself.
>

Same problem with "empty" and optional<vector<int>>.  Which is empty,
the optional or the inner container?

Maybe a better term is "nonvalue" or notavalue or something.  Or
always say "disengaged".  But should "nullopt" be called something
else?

Tony

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