RE: [boost] Infinite number of parameters?

From: Brock Peabody (brock.peabody_at_[hidden])
Date: 2003-08-05 10:24:46

That's a cool idea.  It's a lot prettier than using the preprocessor.

Does anyone know whether or not a language solution is being considered
for this or variable class template arguments?

> -----Original Message-----
> From: boost-bounces_at_[hidden]
[mailto:boost-bounces_at_[hidden]]
> On Behalf Of Philippe A. Bouchard
> Sent: Monday, August 04, 2003 9:39 PM
> To: boost_at_[hidden]
> Subject: [boost] Infinite number of parameters?
> 
> Hello,
> 
>     Often some function and functors requires to be overloaded N times
to
> handle undefinite number of arguments, depending on some default
setting.
> Maybe the following could be used; it overloads operator , () and
> gradually
> creates a typelist.  This typelist is used to replace the undefinite
> number
> of arguments:
> 
> #include <iostream>
> 
> 
> using namespace std;
> 
> 
> namespace infinite
> {
> 
> 
> template <typename T = void, typename U = void>
>  struct typelist : U
>  {
>   typedef T type;
> 
>   T value;
> 
>   typelist(T const & a, U const & b) : value(a), U(b) {}
>  };
> 
> template <>
>  struct typelist<void, void>
>  {
>   typedef void type;
>  };
> 
> template <typename T>
>  struct typelist<T, void>
>  {
>   typedef T type;
> 
>   T value;
> 
>   typelist(T const & a) : value(a) {}
>  };
> 
> 
> typelist<> const begin = typelist<>();
> 
> 
> }
> 
> 
> template <typename V>
>  infinite::typelist<V, void> operator , (infinite::typelist<> const &,
V
> const & v)
>  {
>   return infinite::typelist<V, void>(v);
>  }
> 
> template <typename T, typename U, typename V>
>  infinite::typelist< V, infinite::typelist<T, U> > operator ,
> (infinite::typelist<T, U> const & t, V const & v)
>  {
>   return infinite::typelist< V, infinite::typelist<T, U> >(v,
> infinite::typelist<T, U>(t));
>  }
> 
> 
> // Usage example:
> 
> template <typename T, typename U>
>  void foo(infinite::typelist<T, U> const & i)
>  {
>   cout << __PRETTY_FUNCTION__ << endl;
>  }
> 
> int main()
> {
>  foo((infinite::begin, true, (char *) "adasd", 12367, 127.2));
> }
> 
> 
> 
> My 0,02$
> 
> Philippe
> 
> 
> 
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