Re: [Boost-users] [fusion][bind] How to bind a fusion sequence?

3 May 2007


      I know about this solution to my problem by defining a function
returning the value I'm looking for. See the get_id() function. My
question is is there a way of doing without defining such a function?

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

typedef fusion::map< fusion::pair< fields::_id_        , string >
                   , fusion::pair< fields::_name_      , string >
                   , fusion::pair< fields::_birthday_  , string >
                   , fusion::pair< fields::_address_id_, string >
                   > table_type;

const string& get_id( const table_type& t )
{
   return fusion::at_key< fields::_id_ >( t );
}

int main()
{
   table_type table;

   vector< table_type > vec;

   find_if( vec.begin()
          , vec.end()
          , bind( equal_to< string >()
                , bind( &get_id, _1 )
                , string( "Hallo" )));

   return 0;
}

On 5/3/07, Christian Henning <chhenning@gmail.com> wrote:
...
Hi there, I have a problem ( compilation error ) using a fusion map
with boost bind. Not sure if that is the intended usage. So, please
show some mercy when I'm doing something totally stupid.
Basically, I have a std::vector of a fusion::map instances. And I
would like to find a fusion::map instance with a special value.
Here is the code:
#include <vector>
#include <algorithm>
#include <functional>
#include <boost/bind.hpp>
#include <boost/fusion/algorithm.hpp>
#include <boost/fusion/sequence.hpp>
#include <boost/fusion/iterator.hpp>
using namespace std;
using namespace boost;
namespace fields
{
   struct _id_;
   struct _name_;
   struct _birthday_;
   struct _address_id_;
}
typedef fusion::map< fusion::pair< fields::_id_        , string >
                   , fusion::pair< fields::_name_      , string >
                   , fusion::pair< fields::_birthday_  , string >
                   , fusion::pair< fields::_address_id_, string >
                   > table_type;
int main()
{
   table_type table;
vector< table_type > vec;
find_if( vec.begin()
          , vec.end()
          , bind( equal_to< string >()
                , bind( &fusion::at_key< fields::_id_ >, _1 )
                , string( "Hallo" )));
return 0;
}
Does that makes sense? If yes, how would I do it?
I'm using MSVC 7.1 and the first couple of compiler errors are:
Compiling...
test.cpp
test.cpp(43) : error C2783: 'result_of::at_key<const
Sequence,Key>::type boost::fusion::at_key(const Sequence &)' : could
not deduce template argument for 'Sequence'
        c:\boost\boost\fusion\sequence\intrinsic\at_key.hpp(50) : see
declaration of 'boost::fusion::at_key'
test.cpp(43) : error C2783:
'lazy_disable_if<boost::is_const<Sequence>,boost::fusion::result_of::at_key<Sequence,Key>>::type
boost::fusion::at_key(Sequence &)' : could not deduce template
argument for 'Sequence'
        c:\boost\boost\fusion\sequence\intrinsic\at_key.hpp(43) : see
declaration of 'boost::fusion::at_key'
test.cpp(43) : error C2784:
'boost::_bi::bind_t<R,boost::_mfi::dm<R,T>,_bi::list_av_1<A1>::type>
boost::bind(R T::* ,A1)' : could not deduce template argument for
'overloaded function type' from 'overloaded function type'
        c:\boost\boost\bind.hpp(1616) : see declaration of 'boost::bind'
[snip]
Thanks for your patients,
Christian