On 8/29/2012 7:10 AM, Agustín K-ballo Bergé wrote:
I'm looking for a way to create a Fusion sequence wrapper that is itself a Fusion sequence and forwards all 'calls' to its wrapped sequence. Something in the lines of
template< typename Sequence > struct sequence_wrapper { explicit sequence_wrapper( Sequence const& s ) : seq( s ){}
Sequence seq; };
where sequence_wrapper< Sequence > is a Fusion sequence as well, and works just as Sequence would. The reason I need this is that I have several functions that operate on Fusion sequences (where all elements satisfy some special requirements), and I would like to add some syntax sugar for which I need a custom type to add overloaded operators to. I do not need the result of operations on a sequence_wrapper to return a sequence_wrapper as well, only the syntax sugar related calls would return a (manually) wrapped sequence. For instance, appending elements to a sequence using the comma operator (somewhat of a Boost.Assign for Fusion sequences):
template< typename Sequence, typename T > sequence_wrapper< typename boost::fusion::result_of::push_back< Sequence const& , T >::type > operator,( Sequence const& seq, T const& v ) { return sequence_wrapper< typename boost::fusion::result_of::push_back< Sequence const& , T >::type >( boost::fusion::push_back( seq, v ) ) ; }
What would be the best way to achieve this (if it is indeed supported by the library)? I'm particularly trying to avoid creating a Fusion sequence from scratch, as I would like to use whatever sequence is returned by Fusion operations. Would inheritance + specialization of `tag_of` to return the tag of the wrapped sequence just work? Or will I need to define a tag of my own and implement all required functions to just forward the call?
I do not know an easy way other than using the Sequence Facade: http://tinyurl.com/8k5wq5p Regards, -- Joel de Guzman http://www.boostpro.com http://boost-spirit.com