Hi all, I am trying to read a graphviz file into my graph implementation. The minimum working code as well as the graphviz file are at the end of this e-mail. The node of the graph is the Vertex struct, which contains a point object (Point p). For Point class, I overload two operators, >> and <<, and operator << was previously used to generate the graphviz file. The operator overloads work well with std::cin and std::cout, but with the code below, I receive an exception: bad lexical cast: source type value could not be interpreted as target . The culprit might be in the << overload. In particular, when reading from a file, the value of iToBool1 is true, whereas iToBool2 is false. That is to say, the variable i might change when inserting the stream data to the point. This does not happen when reading from std::cin, as both variables are true. I convert the i variable, originally an istream, to bool because when the program returns to the calling function, which is lexical_stream_limited_src::shr_using_base_class on line 1616 in lexical_cast.hpp, this functions uses the return value of << operator in a boolean comparison. The value of iToBool2 being false eventually leads to calling BOOST_LCAST_THROW_BAD_CAST on line 1975. I wonder if somebody can tell me what is wrong with my operator overload? I use Boost 1.50 and Visual Studio 2008 on Windows 7. Thanks! Best regards, Nicholas //--------------------Graphviz-------------------- graph G { 1 [Point="1 2 3"]; } //----------------------code---------------------- #include <boost/graph/adjacency_list.hpp> #include <boost/property_map/dynamic_property_map.hpp> #include <boost/graph/graphviz.hpp> #include <iostream> #include <fstream> #include <string> struct Point { float x; float y; float z; inline friend std::istream& operator >> ( std::istream& i, Point& p ) { bool iToBool1 = i; i >> p.x >> p.y >> p.z; bool iToBool2 = i; return i; } inline friend std::ostream& operator << ( std::ostream& o, const Point& p ) { o << p.x << " " << p.y << " " << p.z; return o; } }; struct Vertex { int ID; Point p; }; struct Edge { int ID; }; typedef boost::adjacency_list< boost::listS, boost::vecS, boost::undirectedS, Vertex, // bundled data Edge, // bundled data boost::no_property, // not needed boost::listS> Graph; int main() { // Part 1: input via std::cin Point p; std::cin >> p; Graph graph; // Part 2: input from graphviz boost::dynamic_properties dynamicProperties; dynamicProperties.property("NodeID", boost::get(&Vertex::ID, graph)); dynamicProperties.property("Point", boost::get(&Vertex::p, graph)); dynamicProperties.property("EdgeID", boost::get(&Edge::ID, graph)); std::ifstream file("graph.txt"); try { boost::read_graphviz(file, graph, dynamicProperties, "NodeID"); } catch (std::exception& e) { std::cout << e.what() << std::endl; } return 0; }