using templates in templates

[John Harrison]

template<class TYPE, class ELEMENT>
class MyClass : public TYPE<ELEMENT,ELEMENT>
{
};

This does not seem to work - but why?

Because it makes my head hurt?

john

 

[Torsten Curdt]

template<class TYPE, class ELEMENT>
class MyClass : public TYPE<ELEMENT,ELEMENT>
{
};

This does not seem to work - but why?

 

[Jakob Bieling]

template<class TYPE, class ELEMENT>
class MyClass : public TYPE<ELEMENT,ELEMENT>
{
};

This does not seem to work - but why?

You are using the wrong syntax. You need to specify that you want TYPE
to be a template class that takes two typename-parameters (or
class-parameters, it is the same thing), like this:

template <template <class T, class U> class TYPE, class ELEMENT>
class MyClass : public TYPE <ELEMENT,ELEMENT>
{
};

hth

 

[Greg P.]

template <template <class T, class U> class TYPE, class ELEMENT>
class MyClass : public TYPE <ELEMENT,ELEMENT>

God what a headache! Generalizing the generalized! =/

 

[Jakob Bieling]

ok, but then I would need to use the template like this, right?

MyClass< Base<A,B> >

No, because a) Base<A,B> is no template class anymore (it is treated
like a regular class type) and b) MyClass takes two template parameters, but
you pass only one.

but because usually A == B I'd like to write

MyClass< Base, A >

If 'Base' is a template class and 'A' is a typename, then this is how
you would write it, yes.

but now I understand: "Base" is not a regular but a class
template - that's why, right?

Any way to work around this?

To work around what? You wrote, you would like to write "MyClass <Base,
A>" (and I assume 'Base' is a template class and 'A' is a typename), which
is exactly how you are supposed to write it.

hth

 

[Torsten Curdt]

To work around what? You wrote, you would like to write "MyClass <Base,

A>" (and I assume 'Base' is a template class and 'A' is a typename), which
is exactly how you are supposed to write it.

ok, thanks

too bad but the compiler doesn't like nested templates

 

[Tobias Langner]

ok, thanks

too bad but the compiler doesn't like nested templates

gcc does

 

[Jakob Bieling]

ok, thanks

too bad but the compiler doesn't like nested templates

Which one are you using? VC++ 7.1 supports them.

 

[Torsten Curdt]

Which one are you using? VC++ 7.1 supports them.

eVC++ 4

In the help there is even an example of nested templates
but the compilers complains anyway :-/