"typedef templates" inside templates - how can I do this?

[Sacha]

I'm aware, that up to date, "typedef templates" are not defined within
the C++ standard. The seemingly common workaround is this:
template <class T> struct MyTypeDef
{
/* ultimately I need something like this:
MyOtherClass<T> Type;
but let's keep it simple for the moment */

typedef short Type;
};

// I now can use this pseudo typedef template like this:

MyTypeDef<int>::Type foo;
// but this does not compile (MSVC):

template <class T> class MyClass {
MyTypeDef<T>::Type foo;
};
Is there a typo in my code, or is there some fundamental limitation that
prohibits the typedef template workaround in this situation?

-Sacha

[deane_gavin]

Sacha wrote:

I'm aware, that up to date, "typedef templates" are not defined within
the C++ standard. The seemingly common workaround is this:
template <class T> struct MyTypeDef
{
/* ultimately I need something like this:
MyOtherClass<T> Type;
but let's keep it simple for the moment */

typedef short Type;
};

// I now can use this pseudo typedef template like this:

MyTypeDef<int>::Type foo;
// but this does not compile (MSVC):

template <class T> class MyClass {
MyTypeDef<T>::Type foo;
typename MyTypeDef<T>::Type foo;
};

Gavin Deane

[John Carson]

"Sacha" <sa**********@unibas.ch> wrote in message
news:43**************@unibas.ch

I'm aware, that up to date, "typedef templates" are not defined within
the C++ standard. The seemingly common workaround is this:
template <class T> struct MyTypeDef
{
/* ultimately I need something like this:
MyOtherClass<T> Type;
but let's keep it simple for the moment */

typedef short Type;
};

// I now can use this pseudo typedef template like this:

MyTypeDef<int>::Type foo;
// but this does not compile (MSVC):

template <class T> class MyClass {
MyTypeDef<T>::Type foo;
};

Make that

template <class T> class MyClass {
typename MyTypeDef<T>::Type foo;
};
--
John Carson

[Neelesh Bodas]

Sacha wrote:

template <class T> class MyClass {
MyTypeDef<T>::Type foo;
typename MyTypeDef<T>::Type foo;

This will work.
Is there a typo in my code, or is there some fundamental limitation that
prohibits the typedef template workaround in this situation?
Not a typo really. But typenames inside template qualified with the
template parameter must be accompanied by the keyword "typename", else
they will be treated as static variables.

-Sacha

[Ben Pope]

Sacha wrote:

I'm aware, that up to date, "typedef templates" are not defined within
the C++ standard. The seemingly common workaround is this:
template <class T> struct MyTypeDef
{
/* ultimately I need something like this:
MyOtherClass<T> Type;
but let's keep it simple for the moment */

typedef short Type;
// Should that be
typedef T Type;
};

// I now can use this pseudo typedef template like this:

MyTypeDef<int>::Type foo;
// but this does not compile (MSVC):

template <class T> class MyClass {
MyTypeDef<T>::Type foo;
// Have to let the compiler know about the dependant type.
typename MyTypeDef<T>::Type foo;
};
Is there a typo in my code, or is there some fundamental limitation that
prohibits the typedef template workaround in this situation?

Does that sort you out?

Ben Pope
--
I'm not just a number. To many, I'm known as a string...