Re: [Boost-users] [boost] [fusion] fusion::map doesn't define 'category'

D'oh - I found the error: typedef typename fusion::result_of::as_map type; should be typedef typename fusion::result_of::as_map::type type; On 27 July 2012 13:48, Steve Lorimer wrote:

I am attempting to create a fusion map which looks like:

map< pair, pair >

I am then attempting to find out if *field1 *exists in the map using *has_key, *but am getting a compile error:

error: no type named ‘category’ in ‘struct boost::fusion::result_of::as_map, boost::fusion::pair > >

Can anyone offer insight on what I'm doing wrong?

I have a simple example below:

#include <iostream> #include #include #include #include #include

namespace fusion = boost::fusion; namespace mpl = boost::mpl;

*// given a field, returns a fusion pair of * template<class field> struct make_pair { typedef typename fusion::result_of::make_pair::type type; };

*// given a sequence of fields, returns a fusion map which maps field -> field::type* template<class fields> struct make_map { typedef typename mpl::transformmpl::_1>::type pair_sequence; typedef typename fusion::result_of::as_map type; };

*// sets boolean value to true if field is in fields* template struct contains_key { typedef typename boost::fusion::vector vector; typedef typename make_map<vector>::type map; typedef typename fusion::result_of::has_key::type result;

static const bool value = result(); };

struct field1 { typedef int type; }; struct field2 { typedef int type; };

int main() { std::cout << contains_key::value << std::endl; return 0; }