Re: [Boost-users] [variant] make_recursive_variant containing a variant ?

From: Alban Linard (alban.linard_at_[hidden])
Date: 2008-02-26 16:35:32

Steven Watanabe wrote:

> AMDG
> 
> Alban Linard wrote:
> 
>>Hi,
>>
>>i am trying to build a recursive variant containing another variant, as 
>>described in the following source code:
>>
>>#include <cstdlib>
>>#include <vector>
>>#include <string>
>>#include <boost/variant.hpp>
>>
>>typedef ::boost::variant
>>         < int
>>         , bool
>>         >
>>         first_variant;
>>
>>typedef ::boost::make_recursive_variant
>>         < first_variant
>>         , ::std::string
>>         , ::std::vector< ::boost::recursive_variant_ >
>>         >::type
>>         second_variant;
>>
>>int main()
>>{
>>   first_variant f(true);
>>   second_variant s(f);
>>   return EXIT_SUCCESS;
>>}
>>
>>It does not compile (g++-4.0 and g++-4.3). It seems that the 
>>"first_variant" part of second_variant is not used.
>>Why this behavior ? Is there a workaround ?
>>  
> 
> 
> This is a bug in boost::variant.  You can fix it by changing line 101 of 
> boost/variant/recursive_variant.hpp
> from
>     typedef ::boost::variant< types > type;
> to
>     typedef ::boost::variant< over_sequence<types> > type;
> 
> In Christ,
> Steven Watanabe

Thank you very much!

Next step, i would like to store a container of first_variant instead of 
   a single one.

#include <cstdlib>
#include <vector>
#include <boost/variant.hpp>

typedef ::boost::variant
         < int
         , bool
         >
         first_variant;

typedef ::boost::make_recursive_variant
         < ::std::vector< first_variant >
         , ::std::vector< ::boost::recursive_variant_ >
         >::type
         second_variant;

int main()
{
   ::std::vector< first_variant > f;
   second_variant s(f);
   return EXIT_SUCCESS;
}

This crashes, too. Again, did i use it wrong or is it another problem ?

Thanks,
Alban Linard