Alexandre Oliva <oliva@dcc.unicamp.br> wrote:

>Brian Parker writes:

>> Can anyone please tell me whether the  typenames in the following
>> example are required, or are, in fact, disallowed?

>> template<class T>
>> void Func(T t ){
>>  return Func2<typename T::type_nontype>( Traits<typename T::type>() );
>> }

>It must be decided at the declaration point whether T::type_nontype
>and T::type name a type or a value, so the keyword typename is
>required if you're supposed to refer to a type, and required not to be
>present if you're referring to a non-type.

Thanks for your response, I suppose I will send this example off as a
VC 5.0 bug report.

BTW, here is another minor example I didn't include in the original
posting-

template<class T, class i =T::i>
class C {};

Clearly the T::i above doesn't need a "typename" qualification and I
am pretty sure the draft doesn't intend for one to be used, but the
wording of 14.6 [temp.res] suggests it is required.

Anyone have any thoughts on this example?

,Brian Parker (bparker@gil.com.au)
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Greetings all,

I have recently been randomly sprinkling "typename" throughout my code
and have come across another example where I am uncertain as to
whether it is required or not.

Can anyone please tell me whether the  typenames in the following
example are required, or are, in fact, disallowed?

template<class T>
void Func(T t ){
 return Func2<typename T::type_nontype>( Traits<typename T::type>() );
}

Func2 may have valid instantiations regardless of whether
T::type_nontype is a type or a non-type and so I presume that typename
would be optional here, or will the compiler complain if I use
typename but later T::type_nontype turns out to be a non-type.

For T::type, is the compiler supposed to check Traits<> to ensure that
it takes a type parameter, or must the compiler  accept the code
regardless.

Visual C++ 5.0 disallows both typenames.

,Brian Parker (bparker@gil.com.au)
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Brian Parker writes:

> Can anyone please tell me whether the  typenames in the following
> example are required, or are, in fact, disallowed?

> template<class T>
> void Func(T t ){
>  return Func2<typename T::type_nontype>( Traits<typename T::type>() );
> }

It must be decided at the declaration point whether T::type_nontype
and T::type name a type or a value, so the keyword typename is
required if you're supposed to refer to a type, and required not to be
present if you're referring to a non-type.

--
Alexandre Oliva
mailto:oliva@dcc.unicamp.br mailto:aoliva@acm.org
Universidade Estadual de Campinas, SP, Brasil
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