Typedef of a template?

[Richard van Wegen]

Dear All

I'm hoping someone can show me the correct way to typedef a template
class -
i.e. something along the lines of

typedef boost::shared_p tr<T> shared_ptr_mult ithread<T>;

(syntax is obviously wrong but you get the idea)

i.e. I want to be able to write

int main()
{
shared_ptr_mult ithread<MyClass > my_class_multit hreaded_ptr;
shared_ptr<MyCl ass> my_class_single threaded_ptr;
}

so that for the time being it is equivalent to
int main()
{
shared_ptr<MyCl ass> my_class_multit hreaded_ptr;
shared_ptr<MyCl ass> my_class_single threaded_ptr;
}

but later on I can change the way that shared_ptr_mult ithread<MyClass >
is
implemented without affecting all my other shared_ptr<MyCl ass>
declarations.

I'm sure it must be simple, but I can't find the syntax for it
anywhere and I've tried all the combinations of "template" and
"typename" etc I can think of with no success. (GCC 2.96). At the
moment I'm forced to rely on #define (eugh).

Thanks for any pointers!
Richard

[John Harrison]

Re: Typedef of a template?


"Richard van Wegen" <spamblackhole@ volcanomail.com > wrote in message
news:c74f7092.0 307132234.507c5 096@posting.goo gle.com...[color=blue]
> Dear All
>
> I'm hoping someone can show me the correct way to typedef a template
> class -
> i.e. something along the lines of
>
> typedef boost::shared_p tr<T> shared_ptr_mult ithread<T>;
>
> (syntax is obviously wrong but you get the idea)
>
> i.e. I want to be able to write
>
> int main()
> {
> shared_ptr_mult ithread<MyClass > my_class_multit hreaded_ptr;
> shared_ptr<MyCl ass> my_class_single threaded_ptr;
> }
>
> so that for the time being it is equivalent to
> int main()
> {
> shared_ptr<MyCl ass> my_class_multit hreaded_ptr;
> shared_ptr<MyCl ass> my_class_single threaded_ptr;
> }
>
> but later on I can change the way that shared_ptr_mult ithread<MyClass >
> is
> implemented without affecting all my other shared_ptr<MyCl ass>
> declarations.
>
> I'm sure it must be simple, but I can't find the syntax for it
> anywhere and I've tried all the combinations of "template" and
> "typename" etc I can think of with no success. (GCC 2.96). At the
> moment I'm forced to rely on #define (eugh).
>
> Thanks for any pointers!
> Richard[/color]

You cannot write template typedefs, its a limitiation of the C++ syntax
(soon to be corrected?).

The best you can do is wrap your typedefs in a struct, which can be
templated.

template <class T>
struct Type
{
typedef boost::shared_p tr<T> shared_ptr_mult ithread;
typedef boost::shared_p tr<T> shared_ptr; // or something
};

int main()
{
Type::shared_pt r_multithread<M yClass> my_class_multit hreaded_ptr;
Type::shared_pt r<MyClass> my_class_single threaded_ptr;
}

john

[John Harrison]

Re: Typedef of a template?


"Sarah Thompson" <sarah@telergy. remove.this.bit .com> wrote in message
news:betma4$n2m $1$830fa79f@new s.demon.co.uk.. .[color=blue]
>
>
> John Harrison wrote:[color=green]
> > You cannot write template typedefs, its a limitiation of the C++ syntax
> > (soon to be corrected?).
> >
> > The best you can do is wrap your typedefs in a struct, which can be
> > templated.
> >
> > template <class T>
> > struct Type
> > {
> > typedef boost::shared_p tr<T> shared_ptr_mult ithread;
> > typedef boost::shared_p tr<T> shared_ptr; // or something
> > };
> >
> > int main()
> > {
> > Type::shared_pt r_multithread<M yClass> my_class_multit hreaded_ptr;
> > Type::shared_pt r<MyClass> my_class_single threaded_ptr;
> > }[/color]
>
> That should be written as:
>
> int main()
> {
> Type<MyClass>:: shared_ptr_mult ithread my_class_multit hreaded_ptr;
> Type<MyClass>:: shared_ptr my_class_single threaded_ptr;
> }
>
> shouldn't it?
>[/color]

Yes indeedy, thanks.

john

[Richard van Wegen]

Re: Typedef of a template?

> > > You cannot write template typedefs, its a limitiation of the C++ syntax[color=blue][color=green][color=darkred]
> > > (soon to be corrected?).
> > >
> > > The best you can do is wrap your typedefs in a struct, which can be
> > > templated.
> > >
> > > template <class T>
> > > struct Type
> > > {
> > > typedef boost::shared_p tr<T> shared_ptr_mult ithread;
> > > typedef boost::shared_p tr<T> shared_ptr; // or something
> > > };[/color]
> >
> > int main()
> > {
> > Type<MyClass>:: shared_ptr_mult ithread my_class_multit hreaded_ptr;
> > Type<MyClass>:: shared_ptr my_class_single threaded_ptr;
> > }[/color][/color]

Ah ok, that explains why I was having so much trouble.

Thanks very much to you both for the help!

Cheers
Richard