Question

I am trying to create something like a list. However, different instances of the list may have a different number of entries, and the type of entry is based on input given by the user. For example, the user states that they want the structure of each entry in the list to contain an int id, a std::string name, a double metricA, and a long metricB. Based on this input, the following is created:

struct some_struct {
    int id;
    std::string name;
    double metricA;
    long metricB;
}

list<some_struct> some_list;

The user input may be read from a file, input on the screen, etc. Additionally, their are a variable number of entries in some_struct. In other words, it may have the entries listed above, it may have just 2 of them, or it may have 10 completely different ones. Is there someway to create a struct like this?

Additionally, being able to apply comparison operators to each member of some_struct is a must. I could use boost::any to store the data, but that creates issues with comparison operators, and also incurs more overhead than is ideal.

Answer 1

I ended up using a list with a boost::variant. The performance was far better than using boost::any. It went something like this:

#include <boost/variant/variant.hpp>
#include <list>

typedef boost::variant< short, int, long, long long, double, string > flex; 
typedef pair<string, flex> flex_pair;
typedef list< flex_pair > row_entry;

list< row_entry > all_records;