Re: [Boost-users] Multiple templates singletons

From: Ovanes Markarian (om_boost_at_[hidden])
Date: 2008-01-24 09:52:28

Tobias,

Thanks for your corrections. It is a bit difficult to speak by means of
"C++-Standard Language" ;)

With Kind Regards,
Ovanes

P.S.
---- OFFTOPIC
Could you take a look at my previous posting regarding singleton
destruction. May be you have overseen it.
---- END

On Jan 24, 2008 3:26 PM, Tobias Schwinger <tschwinger_at_[hidden]> wrote:
  [...]

> The wording is a bit ambiguous: A pointer to an /incomplete type/ is in
> fact OK (using standard terminology), but 'TreeImplBase' is a /template
> id/ which is not a type at all.
>
> As Ovanes pointed out that construct is illegal, however (except inside
> a definition of 'TreeImplBase' where it's the /injected class name/).
>
> /Specializing/ a template with template arguments yields a type. Using
> (whatever) member of this type's interface causes the template to be
> implicitly (possibly partially) /instantiated/. It's most important to
> realize that specializing a template does not cause the template to be
> instantiated automatically.
>
> Note that "template specialization" has a context-dependent meaning, as
> it can either refer to a type or of a class (template) definition of a
> variant implementation of the template:
>
>     // /primary template/
>     template< typename T > struct A { ... };
>
>     // definition of the (full) specialization A<int>
>     template< > struct A<int> { ... };
>
>     // definition of a partial specialization
>     template< typename T > struct A< B<T> >
>     {
>         typedef A self; // /injected class name/ is a type
>     };
>
>     // X and Y are specializations (not instantiations)!
>     typedef A< B<int> > X;
>     typedef A< long > Y;
>
>     int main()
>     {
>        X x; // instantiation of the 'B<int>'-specialization of A
>        // at this point
>
>     // ...
>
> OK, that's about template terminology in five minutes :-).
>
>
> Regards,
> Tobias
>
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