如何使用Boost读取点文件的pos属性？

Question

我有以下cpp文件：

#include <iostream>                  // for std::cout
#include <utility>                   // for std::pair
#include <algorithm>                 // for std::for_each
#include <boost/graph/graph_traits.hpp>
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/dijkstra_shortest_paths.hpp>
#include <boost/graph/graphviz.hpp>

using namespace boost;
using namespace std;

  int main(int,char*[])
  {
    // create a typedef for the Graph type
    typedef adjacency_list<vecS, vecS, bidirectionalS> Graph;

     // declare a graph object
    Graph g();
    dynamic_properties dp;


    ifstream dotfile ("./a1.dot");

    read_graphviz(dotfile,g, dp);


    return 0;
  }

其中a1.dot是：

digraph G {
    graph [bb="0,0,147,324"];
    node [label="\N"];
    0    [height=0.5,
        pos="82,306",
        width=0.75];
    1    [height=0.5,
        pos="27,234",
        width=0.75];
    0 -> 1   [pos="e,38.911,250.16 70.066,289.81 62.786,280.55 53.337,268.52 45.146,258.09"];
    3    [height=0.5,
        pos="65,162",
        width=0.75];
    0 -> 3   [pos="e,67.058,180.19 79.949,287.87 77.052,263.67 71.729,219.21 68.279,190.39"];
    1 -> 3   [pos="e,56.234,179.15 35.813,216.76 40.418,208.28 46.155,197.71 51.321,188.2"];
    2    [height=0.5,
        pos="120,90",
        width=0.75];
    2 -> 0   [pos="e,85.045,287.85 116.99,107.94 110.42,144.92 94.75,233.2 86.8,277.97"];
    4    [height=0.5,
        pos="92,18",
        width=0.75];
    2 -> 4   [pos="e,98.588,35.47 113.36,72.411 110.09,64.216 106.06,54.14 102.38,44.955"];
    3 -> 2   [pos="e,108.09,106.16 76.934,145.81 84.214,136.55 93.663,124.52 101.85,114.09"];
    3 -> 4   [pos="e,88.732,36.189 68.257,143.87 72.858,119.67 81.312,75.211 86.791,46.393"];
}

我试图在cpp文件中打印pos属性，有人可以给我任何指示或告诉我它是如何完成的吗？

谢谢？