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From: "Gabor Greif" <gabor@no.netopia.com>
Subject: Re: [Q] Dependent template arguments
Date: 2000/06/30
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On Thu, Jun 29, 2000 7:16 Uhr, Stephen Cleary <mailto:csclear@my-deja.com>
wrote:
>In article <B575744D-A430A@192.109.102.124>,
>  "Gabor Greif" <gabor@no.netopia.com> wrote:
>> I am evaluating what degree of dependency of template arguments is
>> permitted by the standard...
>>
>> template <typename T, template <T> class F>
>> struct foo {};
>>
>> Admittedly my example is rather contrived, but I did not find any
>hint in
>> the standard that this kind of dependency would be disallowed.
>
>Since F is a template template argument, it needs a template parameter
>list.  "<T>" is not a template parameter list.

You seem to confuse things here.

In my example F would be a template template argument of foo
and T the _kind_ of an unnamed (non-type) template argument of F.


I also could have written

template <typename T, template <T ARG> class F>
struct foo {};
(you mention this form in your reply)

but writing ARG is redundant just as parameter names in function pointer
types.

Assume I want to instantiate foo with int as the first parameter:

foo<int, TEMPLATE>();

then TEMPLATE must be a class template defined thus:

template <int I>
struct TEMPLATE {};

Hope this makes things clear.

But my original question still goes unanswered. Is the demonstrated
dependency of template arguments legal by the standard? If no, why and if
yes, are there compilers that support it?

	Gabor


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