siemelnaran@my-deja.com wrote:
>
> struct Junk
> {
>    template <class T> Junk();
> };
>
> How do I create a Junk object initialized with Junk::Junk() with T==int.

You can't. As section 14.8.1p5 says: "[_Note:_ because the explicit
template argument list follows the function template name, and because
conversion member function templates and constructor member function
templates are called without using a function name, there is no way to
provide an explicit template argument list for these function
templates.]"

What you need is to give it an argument which allows the template type
to be deduced implicitly:

 template <class T> Junk(const T&);

The constructor doesn't have to do anything with the argument, it just
needs to have it. Then you can invoke it with, for instance,

 Junk junk((int)5);

If there's some major overhead to creating an object of type T, such
that you don't want to have to create one just for the purpose of
constructing a Junk<T>, then an alternative would be to use a helper
template, whose sole purpose is to abstract out the type information for
a given type:

 template <class T> Abstract
 {
  typedef T type; // Not actually used in this example

  // Default constructor implicitly declared and
  // implicitly defined as a no-op.
 };

 template <class T> Junk(const Abstract<T>&);

Then you can create a Junk() using the 'int' version of the constructor
by writing the following:

 Junk junk(Abstract<int>());
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siemelnaran@my-deja.com wrote:
>
> struct Junk
> {
>    template <class T> Junk();
> };
>
> How do I create a Junk object initialized with Junk::Junk() with T==int.
>
> Junk<int> junk; // but the outer object has Junk<int>
>
> Junk junk<int>; // could this be it?
>
You can't do this at all.  What on earth does this mean?  You can provide
multiple constructors only when they have differening arguments.

It's not clear what you are trying to do.  I suspect maybe the following
construct may work for you:

struct CommonJunk {
 // most of what is in your junk class.
};

template <typename T> struct Junk : CommonJunk {
 Junk() { };
};

You can then use the specialized Junks to initialize objects
of type CommonJunk (or references/pointers to them).
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<siemelnaran@my-deja.com>:
> struct Junk
> {
>    template <class T> Junk();
> };
>
> How do I create a Junk object initialized with Junk::Junk() with T==int.
>
> Junk<int> junk; // but the outer object has Junk<int>
>
> Junk junk<int>; // could this be it?

Junk junk = Junk<T>();

sm
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<siemelnaran@my-deja.com> wrote...
> struct Junk
> {
>    template <class T> Junk();
> };
>
> How do I create a Junk object initialized with Junk::Junk() with
T==int.
>
> Junk<int> junk; // but the outer object has Junk<int>
>
> Junk junk<int>; // could this be it?

I am sorry, I don't have an answer yet.  But I have a question
for you: why a templated c-tor with no arguments in a non-templated
class?

Victor
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hi,
siemelnaran@my-deja.com wrote:
>
> struct Junk
> {
>    template <class T> Junk();
> };
>
> How do I create a Junk object initialized with Junk::Junk() with T==int.
>
> Junk<int> junk; // but the outer object has Junk<int>
>
> Junk junk<int>; // could this be it?
>
i would say it's impossible. The constructor of a class is strictly
bound to the type (class) to construct. What do you want do gather
from this construct?

regards
Torsten
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10 Feb 2001 12:20:00 -0500, James Kuyper Jr. <kuyper@wizard.net> pisze:

> If there's some major overhead to creating an object of type T, such
> that you don't want to have to create one just for the purpose of
> constructing a Junk<T>, then an alternative would be to use a helper
> template, whose sole purpose is to abstract out the type information for
> a given type:

Or just the null pointer of type T.

--
 __("<  Marcin Kowalczyk * qrczak@knm.org.pl http://qrczak.ids.net.pl/
 \__/
  ^^                      SYGNATURA ZAST   PCZA
QRCZAK

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In article <9619ol$sv0$1@nnrp.atgi.net>,
  "Victor Bazarov" <vAbazarov@dAnai.com> wrote:

> I am sorry, I don't have an answer yet.  But I have a question
> for you: why a templated c-tor with no arguments in a non-templated
> class?

To add creatable objects to my registry before entering main().  I
would write this in the respective cpp files --

Registry::Add add<Check>;
Registry::Add add<Withdrawal>;


I ended up just making the whole class Registry::Add into a template,
and I made it's only 2 functions (the constructor and the destructor)
inline and defined in the header file.

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In article <3A83F25D.C80F7FDE@wizard.net>,
  "James Kuyper Jr." <kuyper@wizard.net> wrote:

> The constructor doesn't have to do anything with the argument, it just
> needs to have it. Then you can invoke it with, for instance,
>
>  Junk junk((int)5);
>
> If there's some major overhead to creating an object of type T, such
> that you don't want to have to create one just for the purpose of
> constructing a Junk<T>, then an alternative would be to use a helper
> template, whose sole purpose is to abstract out the type information
for
> a given type:

No.  Use a pointer.  I did this for my dynamic_ptr class because MSVC
doesn't support the .template notation.

template <class T>
template <class U>
U * dynamic_ptr<T>::dynamic_release(U *) {
   U * out=dynamic_cast<U *>(this->d_ptr);
   assert(out);
   this->d_ptr=0;
   return out;
}

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"Sebastian Moleski (SurakWare)" wrote:
>
> <siemelnaran@my-deja.com>:
> > struct Junk
> > {
> >    template <class T> Junk();
> > };
> >
> > How do I create a Junk object initialized with Junk::Junk() with T==int.
> >
> > Junk<int> junk; // but the outer object has Junk<int>
> >
> > Junk junk<int>; // could this be it?
>
> Junk junk = Junk<T>();

Not quite. See 14.8.1p5, which I've already quoted in another message on
this thread.

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struct Junk
{
   template <class T> Junk();
};

How do I create a Junk object initialized with Junk::Junk() with T==int.

Junk<int> junk; // but the outer object has Junk<int>

Junk junk<int>; // could this be it?

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In article <95t9vd$top$1@nnrp1.deja.com>, siemelnaran@my-deja.com writes
>struct Junk
>{
>   template <class T> Junk();
>};
>
>How do I create a Junk object initialized with Junk::Junk() with T==int.
>
>Junk<int> junk; // but the outer object has Junk<int>
>
>Junk junk<int>; // could this be it?

Indeed, it is the constructor that is templated, not the type.




--
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See http://www.accu.org for details of The ACCU Spring Conference, 2001
(includes many regular participants to C & C++ newsgroups)

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