Re: [boost] [Ann] Variadic Templates

From: Davide Bolcioni (davide_bolcioni_at_[hidden])
Date: 2006-08-05 04:40:03

Doug Gregor wrote:

> I have just completed implementing support for "Variadic Templates"  
> in GCC. Variadic templates are C++ templates that can accept any  
> number of "extra" template arguments, just like a function that uses  
> C-style varargs (with "...") can accept any number of extra  
> arguments. Unlike C varags, however, variadic templates work both for  
> class templates and function templates, and are completely type-safe.

A dream come true ...

http://groups.google.com/group/comp.std.c++/browse_frm/thread/9432727bc5e67d48/947b100b5ee21f6e?lnk=st&q=&rnum=9&hl=it#947b100b5ee21f6e

... now I'm going to dig up what my need actually was at the time.

> Unimpressed? Here's an implementation of tuple that accepts any  
> number of element types:
> 
>    template<typename... Values>
>    class tuple;
> 
>    template<> class tuple<> { };
> 
>    template<typename Head, typename... Tail>
>    class tuple<Head, Tail...>
>      : private tuple<Tail...>
>    {
> 
>     protected:
>      Head m_head;
>    };

The fact that head() and tail() are not declareda bove is just an
omission, is it ?

> Are variadic templates worthwhile? Will they help us build better,  
> cleaner Boost libraries in the future? Should we bring variadic  
> templates to the C++ committee, to enable better implementations of  
> TR1 components and eliminate the need for much of the preprocessor  
> metaprogramming we do today? Feedback is greatly appreciated.

Davide Bolcioni
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