[Boost-users] [mpl][fusion] Metafunction for extracting a type from a map

From: Christian Henning (chhenning_at_[hidden])
Date: 2007-03-19 17:59:18

Hi there, next metaprogramming problem. Is it possible to extract a
tagged type from a map?

namespace fields
{
   struct _id_;
   struct _name_;
   struct _birthday_;
   struct _address_id_;
}

namespace tags
{
   struct _primary_key_;
   struct _foreign_key_;
   struct _value_;
}

typedef fusion::map< fusion::vector< fields::_id_ , std::string,
tags::_primary_key_ >
                   , fusion::vector< fields::_name_      ,
std::string, tags::_value_       >
                   , fusion::vector< fields::_birthday_  ,
std::string, tags::_value_       >
                   , fusion::vector< fields::_address_id_,
std::string, tags::_foreign_key_ >
                   > table_type;

int main()
{
 /// how to get the primary key type vector
}

I was looking at fusion's filter_view but that is only available for
non-metaprogramming.

Any ideas?

Christian