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Subject: Re: optional<T>, one more value or two states
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On 27 January 2013 22:48, Daniel James <dnljms@gmail.com> wrote:
>>>     auto x = y;
>>>     *x = 2;
>>> Then for any standard type this is equivalent to assigning '2' to
>>> whatever y points to. By using 'operator*' in std::optional, the
>>> semantics of 'operator*' will be changed. That shouldn't be done
>>> lightly, especially since with templates and 'auto' a type is defined
>>> by the functions and operators that it supports..
>> What semantics does that change? The code assigns to what x points
>> to, x just happens to be optional<T>, which is intrusive and points to
>> the guts of itself. I don't see a semantic violation there.
> x and y point to different things with std::optional. Same code,
> different results = semantic change.

Yes? x and y point to different things also if y is of the proposed
value_ptr type.
They point to different things if y is an auto_ptr. So there are
already exceptions
to this alleged rule, and chances are there's more exceptions coming.

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