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-   -   Choose template return type? (http://www.velocityreviews.com/forums/t459943-choose-template-return-type.html)

Joseph Turian 01-20-2007 02:40 AM

Choose template return type?
 
Examples is a vector of some EXAMPLE type (templated).
ExamplePtrs is a vector of some EXAMPLE* type.
They both contain the same methods, except the latter is dereferencing
pointers whereas the former is just working with EXAMPLE objects
directly.
(I'm sure there's a smarter way to do this with template without
defining two classes, but whatever. It works for me now, and my
question is about something else.)

I want to write a method Examples::ptrs() to return a boost::shared_ptr
to an ExamplePtrs type:

===

template<typename EXAMPLE> class ExamplePtrs;

template <typename EXAMPLE>
class Examples : public vector<EXAMPLE> {
public:
...
template<typename EXAMPLE2> boost::shared_ptr<ExamplePtrs<EXAMPLE2>
> ptrs() const;

};


template <typename EXAMPLE>
class ExamplePtrs : public vector<EXAMPLE*> {
public:
....
}

===

Notice that Examples::ptrs() is templated, because I would like---for
example---to take a Examples<E> and call ptrs() and have it return a
boost::shared_ptr<ExamplePtrs<const E> > (const'ing the ptrs). So far,
the above syntax seems okay. But the question is, how do I call
function ptrs()?

Here's what I'm trying to do, except it doesn't compile:
Examples<E> exmpls;
boost::shared_ptr<ExamplePtrs<const E> > eptrs = exmpls.ptrs<const
E>();

How can I specify the specific type instantiation needed?

Thanks,

Joseph


Victor Bazarov 01-20-2007 03:24 AM

Re: Choose template return type?
 
Joseph Turian wrote:
> [..]
> Here's what I'm trying to do, except it doesn't compile:
> Examples<E> exmpls;
> boost::shared_ptr<ExamplePtrs<const E> > eptrs = exmpls.ptrs<const
>> ();


I think it should be

... eptrs = exmpls.template ptrs<const E>();

> How can I specify the specific type instantiation needed?


It's not the problem in specifying the type, I believe.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask



Joseph Turian 01-20-2007 07:35 PM

Re: Choose template return type?
 
> I think it should be
> .. eptrs = exmpls.template ptrs<const E>();


That worked great, thanks!

Joseph



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