aren't specialized templates templates?

aren't specialized templates templates?

[Tim Janik]

hi all.

the code snippet below is extracted from a much more
complicated piece of code. basically the problem is that
g++ (3.3 and 3.4) demand different typedef syntax inside
template bodies, depending on whether full or partial
specialization is used.

is this really the correct behaviour and standard conform?
(to me it seems, line20 should still be considered part of
a template and thus accept the "typename")

--------------------snip---------------------
template<class C>
struct Base {
   typedef C* Iterator;
};

template<class C, class D>
struct Derived : Base<D> {
   typedef typename Base<D>::Iterator Iterator;
};

#define BASE_ITER(BASE)     typename BASE :: Iterator

template<class D>
struct Derived<char, D> : Base<D> {
   typedef BASE_ITER (Base<D>) Iterator;         // line15
};

template<>
struct Derived<char, int> : Base<int> {
   typedef BASE_ITER (Base<int>) Iterator;       // line20
};

// test.cc:20: error: using `typename' outside of template
--------------------snip---------------------


---
ciaoTJ

Re: aren't specialized templates templates?

[Gabriel Dos Reis]

Tim Janik <timj@gtk.org> writes:

| hi all.
| 
| the code snippet below is extracted from a much more
| complicated piece of code. basically the problem is that
| g++ (3.3 and 3.4) demand different typedef syntax inside
| template bodies, depending on whether full or partial
| specialization is used.
| 
| is this really the correct behaviour and standard conform?

Yes.  An explicit specialization is not a template.  Therefore line20
is in error.

| (to me it seems, line20 should still be considered part of
| a template and thus accept the "typename")
| 
| --------------------snip---------------------
| template<class C>
| struct Base {
|    typedef C* Iterator;
| };
| 
| template<class C, class D>
| struct Derived : Base<D> {
|    typedef typename Base<D>::Iterator Iterator;
| };
| 
| #define BASE_ITER(BASE)     typename BASE :: Iterator
| 
| template<class D>
| struct Derived<char, D> : Base<D> {
|    typedef BASE_ITER (Base<D>) Iterator;         // line15
| };
| 
| template<>
| struct Derived<char, int> : Base<int> {
|    typedef BASE_ITER (Base<int>) Iterator;       // line20
| };
| 
| // test.cc:20: error: using `typename' outside of template
| --------------------snip---------------------
| 
| 
| ---
| ciaoTJ
| 

-- 
                                                       Gabriel Dos Reis 
                                           gdr@integrable-solutions.net

Re: aren't specialized templates templates?

[Martin Sebor]

Tim Janik wrote:
> hi all.
> 
> the code snippet below is extracted from a much more
> complicated piece of code. basically the problem is that
> g++ (3.3 and 3.4) demand different typedef syntax inside
> template bodies, depending on whether full or partial
> specialization is used.
> 
> is this really the correct behaviour and standard conform?
> (to me it seems, line20 should still be considered part of
> a template and thus accept the "typename")

Unfortunately, it is the correct behavior. But because it makes
typename hard to use, a relaxation of the rule that would make
your code well-formed is now being considered. For the status
of this proposed change see:
http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#382

Martin

> 
> --------------------snip---------------------
> template<class C>
> struct Base {
>   typedef C* Iterator;
> };
> 
> template<class C, class D>
> struct Derived : Base<D> {
>   typedef typename Base<D>::Iterator Iterator;
> };
> 
> #define BASE_ITER(BASE)     typename BASE :: Iterator
> 
> template<class D>
> struct Derived<char, D> : Base<D> {
>   typedef BASE_ITER (Base<D>) Iterator;         // line15
> };
> 
> template<>
> struct Derived<char, int> : Base<int> {
>   typedef BASE_ITER (Base<int>) Iterator;       // line20
> };
> 
> // test.cc:20: error: using `typename' outside of template
> --------------------snip---------------------
> 
> 
> ---
> ciaoTJ