c++ - Large POD as tuple for sorting -

i have pod 30 members of various types , wanting store thousands of pods in container, , sort container 1 of members.

for example:

 struct person{    int idnumber;    ....many other members  } 

thousands of person objects want sort idnumber or other member choose sort by.

i've been researching while today , seems efficient, or @ least, simplest, solution not use struct @ all, , rather use tuple can pass index number custom comparison functor use in std::sort. (an example on this page shows 1 way implement type of sort easily, on single member of struct make templating not easy since must refer member name, rather index tuple provides.)

my two-part question on approach 1) acceptable tuple large, dozens of members? , 2) there equally elegant solution continuing use struct instead of tuple this?

you can make comparator stores pointer member internaly knows member take comparison:

struct pod {     int i;     char c;     float f;     long l;     double d;     short s; };  template<typename c, typename t> struct comp {      explicit comp(t c::* p) : ptr(p) {}      bool operator()(const pod& p1, const pod& p2) const     {         return p1.*ptr < p2.*ptr;     }  private:     t c::* ptr; };  // helper function make comparator  template<typename c, typename t> comp<c,t> make_comp( t c::* p) {     return comp<c,t>(p); }  int main() {     std::vector<pod> v;     std::sort(v.begin(), v.end(), make_comp(&pod::i));     std::sort(v.begin(), v.end(), make_comp(&pod::d));     // etc... } 

to further generalize this, make make_comp take custom comparator, can have greater-than , other comparisons.