Re: [Boost-users] [BGL] Unable to sort list of edge_descriptors

Hi, first of all, nice example you specified and also a good idea to include the command-line used to compile. On Sunday, 7. November 2010 05:55:14 Mike Douglass wrote:

I have attached a minimal working program to test the sort function on a list of edges. Compile with : g++ -O3 prog.cpp -o prog

The problem is line "myList.sort(SortByName< graph_t >);" near the bottom of the page. See comments.

Interstingly, the problem is not BGL related. You simply have mixed up some things with using templates here. When you define a struct-template with one parameter, as you do with Graph, then you must also only specify one. You specified a graph_t< edge_t >. However, your graph_t is just a typedef for an adjacency_list and this adjacency_list is not a template. And that's exactly what the compiler is complaining about. So if you change: myList.sort(SortByName< graph_t >); to: myList.sort(SortByName< graph_t >()); your example compiles fine here on my Linux machine. I didn't check if it behaves the way you want it to, but this should be easier to do by yourself when your program is now running. Best, Cedric

//=======================================================================

// Sort Testing Program - prog.cpp

//=======================================================================

#include <iostream> #include <string> #include #include

using namespace boost; using namespace std;

struct vertex_properties {

};

struct edge_properties { string eName; };

typedef adjacency_list < vecS, vecS, bidirectionalS >::edge_descriptor edge_t; typedef adjacency_list < vecS, vecS, bidirectionalS

...

::vertex_descriptor vertex_t; typedef adjacency_list < vecS, vecS, bidirectionalS, vertex_properties, edge_properties > graph_t;

/////////////////////////////////////////////////////////////////////////// /////////////////////////////////////////

template < typename Graph > void add_edges(Graph & g) { // Add some edges with names.

typename graph_traits<Graph>::edge_iterator edge_iter, edges_end;

std::pair< typename graph_traits<Graph>::edge_descriptor, bool > a = add_edge(1,2,g); g[a.first].eName = "A"; std::pair< typename graph_traits<Graph>::edge_descriptor, bool > b = add_edge(1,3,g); g[b.first].eName = "B"; std::pair< typename graph_traits<Graph>::edge_descriptor, bool > c = add_edge(2,1,g); g[c.first].eName = "C"; std::pair< typename graph_traits<Graph>::edge_descriptor, bool > d = add_edge(2,3,g); g[d.first].eName = "D";

cout << endl << " list of edges " << endl; for (tie(edge_iter, edges_end) = edges(g); edge_iter != edges_end; ++edge_iter) cout << " " << g[*edge_iter].eName << endl;

}

template < typename Graph > struct SortByName { // The Predicate

template < typename edge_t > bool operator()(const edge_t& a, const edge_t& b) const { return g[a].eName < g[b].eName; }

Graph g;

};

template < typename Graph > void Sort_Test(Graph & g) { // Test the sort function.

typedef std::list::edge_descriptor> edge_list; typename graph_traits<Graph>::edge_iterator edge_iter, edges_end;

edge_list myList;

// Load myList with the edges of g for (tie(edge_iter, edges_end) = edges(g); edge_iter != edges_end; ++edge_iter) myList.push_back(*edge_iter);

// Write out myList cout << endl << " myList " << endl; for (edge_list::iterator i = myList.begin(); i != myList.end(); ++i) cout << " " << g[*i].eName << endl;

// Sort myList // If the following line is commented out the program compiles and runs OK. myList.sort(SortByName< graph_t >); //With the above line uncommented the compiler says: // "prog.cpp:88: error: ‘graph_t’ is not a template" -- I'm stumped.

}

int main() {

graph_t g;

add_edges(g);

Sort_Test(g);

}

________________________________ From: Cedric Laczny To: boost-users@lists.boost.org Sent: Sat, November 6, 2010 3:54:49 AM Subject: Re: [Boost-users] [BGL] Unable to sort list of edge_descriptors

if my suggestion does not fix the problem, please include a complete example.