c++ - retrieving objects from boost::variant -

i tried ask question before, think way ask question not proper. tried again here: (still don't know subject appropriate)

first defined

typedef boost::variant<point, line, vertex> vec_variant; typedef std::vector<vec_variant> vec; 

the write function such depends on case returns point, line, vertex or combination of them.

vec my_func::select_t(const mesh::section& s, const char* model) const {   vec new_vec;   .   .   .   .  //loop on lines   else if ( strcmp(model , "line") == 0 )   {     for(section::lineiterator ite = s.beginline(); ite != s.endline(); ++ite )     {       line ed = *ite;         point p0 = ed.point(0);         point p1 = ed.point(1);         point p0_modified ( /* modification */  );         point p1_modified ( /* modification */  );           if( /* other conditions */ )         {           new_vec.push_back(ed);           new_vec.push_back(p0_modified); //note before pushing point            new_vec.push_back(p1_modified); //first pushed line         }           else if ( /* other conditions */ )          {            .            .            .            vertex m = .......;            new_vec.push_back(ed);            new_vec.push_back(m);  //note before pushing point                                    //first pushed line          }       }     }   }       return new_vec;     } 

so @ end may have {ed, p0_modified, p0_modified, ed, m, ed, m, ed, p0_modified, p0_modified, ed, m, ....} {line,point,point,line,vertex,line,vertex,line,point,point,line,vertex, ...}

now call function in other part of code (different file)

first defined visitor:      template<typename t>     struct t_visitor : public boost::static_visitor<>     {        t_visitor(std::vector<t>& v) : zerovector(v) {}        template<typename u>        void operator () (const u&) {}        void operator () (const t& value)        {           zerovector.push_back(value);        }     private:        std::vector<t>& zerovector;     }; 

i called above function here :

void func_2( /*......*/ ) {   . //we can use above visitor store each type (point, line, vertex) in vactor<point or line or vertex)   . //we not know new_vec @ end of loop. thing know after each line there   . //would either 2 points or 1 vertex   .   const char *model = "edge";   .   .//how find line ed , corresponded points?   .   create_line( point& p0_modified, point& p1_modified, line& ed);    //two modified points , line   .   .//how find point m , corresponded line?   .   create_point( m(0), m(1), m(2), line& ed);    //point m coordinates , line   .   . } 

so data structure sequence of point, line, , vertex objects (i'm going assume surface in first sentence typo). know additional restriction line must followed either 2 points or 1 vertex. want use structure.

this possible, it's annoying. may recommend change data structure?

struct linewithpoints {   line line;   point p1, p2; }; struct linewithvertex {   line line;   vertex v; }; typedef boost::variant<linewithpoints, linewithvertex> vec_variant; typedef std::vector<vec_variant> vec; 

and change code produce sequence instead. working becomes trivial.