从boost :: variant检索对象

我曾尝试问过我的问题，但我认为我提出问题的方式是不正确的。所以我在这里再次尝试：（仍然不知道哪个主题是合适的）

首先我定义

typedef boost::variant<point, Line, Vertex> vec_variant;
typedef std::vector<vec_variant> vec;

我编写函数的方式取决于它返回点，线，顶点或什至是它们的组合的情况。

vec my_func::select_T(const mesh::section& s, const char* model) const
{
  vec new_vec;
  .
  .
  .
  .
 //loop over my 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 ( /* some modification */  );
        Point p1_modified ( /* some modification */  ); 

        if( /* some other conditions */ )
        {
          new_vec.push_back(ed);
          new_vec.push_back(p0_modified); //note before pushing back any point 
          new_vec.push_back(p1_modified); //first I pushed back line
        }

         else if ( /* some other conditions */ )
         {
           .
           .
           .
           vertex m = .......;
           new_vec.push_back(ed);
           new_vec.push_back(m);  //note before pushing back any point 
                                  //first I pushed back line
         }
      }
    }
  }
      return new_vec;
    }

所以最后我们可能会有这样的内容：{ed，p0_modified，p0_modified，ed，m，ed，m，ed，p0_modified，p0_modified，ed，m，....} {Line，Point，Point，Line，Vertex ，线，顶点，线，点，点，线，顶点，...}

现在，我在代码的另一部分（不同文件）中调用此函数

first I defined a 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;
    };

我在这里调用了上面的函数：

void func_2( /*......*/ )
{
  . //we can use above visitor to store each type (point, line, Vertex) in vactor<point or line or Vertex)
  . //we do not know what the new_vec is at the end of the loop. the only thing we know is that after each line there
  . //would be either two points or one vertex
  .
  const char *model = "Edge";
  .
  .//How to find line ed and corresponded points?
  .
  create_line( Point& p0_modified, Point& p1_modified, Line& ed);    //two modified points and line
  .
  .//How to find point m and corresponded line?
  .
  create_point( m(0), m(1), m(2), Line& ed);    //point m coordinates and line
  .
  .
}