I thought the vector would be type of sub-type, but the elements are
'automatically' super-type on demand i.e. when the compiler detects a
chance for this (built-in) cast. e.g. the compiler cwould automatically
generate some (internal) templates for the super- and sub-types as
needed. There are not many cases - the number of built-in scalar types
(here the super-types) are limited.


*cwould: sorry Mr. Shakespaeare - it is rather late here now.. ( CET :)

On 2024-09-03 00:19, Sebastian Wittmeier via Std-Proposals wrote:
> You could formulate your proposal in a weaker form, where the type is
> used for direct code, but not for template parameters.
>
> If for template parameters the underlying type is used, it would be a
> std::vector<float> all along, and elements taken from the vector would
> be float, not subtype.
>
> Then also the advantages of the subtypes could not be used, when using
> the container.
>
> -----Ursprüngliche Nachricht-----
> *Von:* Karafiát, László via Std-Proposals <std-
> proposals_at_[hidden]>
> *Gesendet:* Mo 02.09.2024 23:53
> *Betreff:* Re: [std-proposals] Fwd: Standardised Type Punning API
> for Wrapper Types
> *An:* Sebastian Wittmeier via Std-Proposals <std-
> proposals_at_[hidden]>;
> *CC:* Karafiát, László <laszlo_at_[hidden]>;
> Well, the subtype of a float for example would automatically be
> 'converted' to float or double (i.e. 'seen' as such when needed) by the
> compiler. Except if you overload or hide that cast in your subtype
> definition. Would this not help?
>
>
> On 2024-09-02 20:06, Sebastian Wittmeier via Std-Proposals wrote:
> > Would it?
> >
> > The sub-types would be different types in the type system, and so
> would
> > be the templated container classes, wouldn't they?
> >
> > Or would the proposal <Scalar Inheritance> use the scalar type for
> > templates?
> >
> > -----Ursprüngliche Nachricht-----
> > *Von:* Karafiát, László <laszlo_at_[hidden]>
> > *Gesendet:* Mo 02.09.2024 18:43
> > *Betreff:* Re: [std-proposals] Fwd: Standardised Type Punning API
> > for Wrapper Types
> > *An:* std-proposals_at_[hidden];
> > *CC:* Sebastian Wittmeier <wittmeier_at_[hidden]>;
> > Hi,
> >
> > my proposal <Scalar Inheritance> would allow sub-typing
> (instead of
> > wrapping) scalar types. Would that be not a clearer and
> better solution?
> >
> > László
> >
> > On 2024-09-02 17:07, Sebastian Wittmeier via Std-Proposals wrote:
> > > How would you know that the container specialization is
> different?
> > >
> > > Or in other words they are always different as it is a
> template.
> > >
> > > At least each container would have to support such a
> facility to
> > remove
> > > the type by itself. Otherwise the implementation details
> could hide
> > > incompatibilities.
> > >
> > > std::vector could support a move_to member function:
> > >
> > > std::vector<my_distance_type> d1;
> > >
> > > // creates a new d2 with new metadata, but keeps the
> convertible
> > actual
> > > data without copying
> > >
> > > // d1 is empty afterwards
> > >
> > > std::vector<double> d2 = d1.move_to<double>();
> > >
> > >
> >
> >
> >
>
> --
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