Hello, I'm trying out some ideas with boost.fusion maps. Here is a small example: namespace fields { struct general { struct first_name ; struct last_name ; struct age ; } ; struct address { struct street ; struct postal_code ; struct country ; } ; } typedef fusion::map < fusion::pair< fields::general::first_name, std::string >, fusion::pair< fields::general::last_name, std::string >, fusion::pair< fields::general::age, int >
general_person ;
typedef fusion::map < fusion::pair< fields::address::street, std::string >, fusion::pair< fields::address::postal_code, std::string >, fusion::pair< fields::address::country, std::string >
address_person ;
typedef fusion::map < fusion::pair< fields::general, general_person >, fusion::pair< fields::address, address_person >
person ;
int main() { using namespace fields ; general_person gp = fusion::make_map< general::first_name, general::last_name, general::age >( "John", "Doe", 99 ) ; address_person ap = fusion::make_map< address::street, address::postal_code, address::country >( "Foo street 1", "12345", "Barland" ) ; person a_person = fusion::make_map< general, address >( gp, ap ) ; std::cout << "Age: " << fusion::at_key< general::age >( fusion::at_key< general >( a_person ) ) << std::endl ; return 0 ; } I'm not happy with the last line that retrieve the value of a specific pair inside a nested map. I was wondering whether this could benefit from some MPL trick to make it more readable. I was thinking about something like the following: get_value< general, age >( a_person ). My questions are: 1) Is MPL the right tool to transform a call to get_value< general, age >( a_person ) into fusion::at_key< general::age >( fusion::at_key< general >( a_person ) ) 2) If it is, could someone provide me some help on how to achieve such a result? Thank you for your help