On 9/5/17 1:02 PM, Steve D'Aprano wrote:
> On Tue, 5 Sep 2017 11:37 pm, Gregory Ewing wrote:
>
>> Dennis Lee Bieber wrote:
>>> Pascal, probably Modula-2, Visual BASIC are closer to the C++ reference
>>> semantics, in that the definition of a function declares how the
>>> argument(s) are passed.
>> Well, sort of. In Pascal and Modula, and also VB I think,
>> parameters are the only things that can be declared as having
>> reference semantics, whereas references in C++ are first-class
>> things that can be stored in any variable.
> No, they aren't first-class.
Did you mis-read Gregory's claim? He said, "references *in C++* are
first-class things". You seem to be talking below about Python things.
>
> - It is not possible to refer to a reference after it is defined; any
> occurrence of its name refers directly to the object it references.
>
> - Since you cannot refer directly to a reference, but only the object
> it points to, you cannot have a reference to a reference.
>
> - Containers of references are not allowed.
>
> - Once a reference to an object is created, it cannot be changed to
> reference another object ("to be reseated").
>
> The last is only a limitation if you think of references as mutable pointers
> in
> the C sense. But if you think of them as objects in the Python sense, that
> makes them merely immutable.
>
> But the inability to refer to the reference itself, the lack of references to
> references, and the inability to have a container of references, makes them
> second-class values -- or possibly not values at all.
>
> (I don't know enough about C++ to distinguish between the last two opinions,
> but
> I'm strongly leaning towards "not values at all".)
>
>
>
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