Re: [Boost-users] Re: is_sequence

From: Wolfgang Meyer (Wolfgang.Meyer_at_[hidden])
Date: 2004-05-11 17:26:12

On Tuesday 11 May 2004 19:09, Rozental, Gennadiy wrote:
> > It already works.  If you want to detect STL sequence-ness, you'll
> > have to try some nasty hacks.  I'm have doubts about whether it's even
> > possible to approximate that metafunction in portable code.
>
> Wouldn't something about these lines work?
>
> template<typename T>
> char test( T const&,  long );
>
> template<typename T>
> int test( std::list<T> const&, int );
>
> template<typename T>
> struct is_list
> {
>     static T t;
>     enum { value = sizeof( test( t, 0 ) ) == 4; }
> };

Thanks for the hint, but I think this would only detect lists - not other 
sequence (vector, deque, possible user defined sequences).

In case someone is interested:
My original objective was to distinguish OutputIterators and Sequences.
So I settled for a solution that checks if the type has a nested type 
"iterator".  Of course, that does not suffice to establish a Sequence, but
for my application it is good enough...

 Wolfgang Meyer