C++0x Wish List: Variadic Template Parameters

[Davide Bolcioni]

Greetings,
I would like to see templates able to take an open-ended set of
arguments, e.g. for a typesafe printf. Something with a syntax like:

// This is the tail case, I could not come up with a
// decent syntax to stop at 0.

template < template <typename Last> ... >
void print(const Last& arg)
{
// In this body, Last is an ordinary typename.
}

// This is the general case.

template < template <typename Head, template Tail> ... >
void print(const Head& head, ...)
{
// In the body, Head is an ordinary typename.
// In the body, Tail is a template not a typename.
sometype x;

print_helper(head);
log(head, x, Tail); // Another variadic function.
print(Tail);
}

print(x, y, z);

On first thought, I would say this should be detailed so that
it is possible to deduce constant expressions as non-type
parameters.

Applying the same syntax to class templates should make the
various typelist efforts much easier and less reliant on the
preprocessor, it seems to me.

Davide Bolcioni
--
Linux - the choice of a GNU generation.

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