boost graph library: named_graph and remove_vertex
I'm experimenting with using the named_graph mixin, and I'm a little confused how remove_vertex() should work.
#include <iostream>
#include <string>
#include <boost/lexical_cast.hpp>
#include <boost/graph/adjacency_list.hpp>
struct vertex_info {
std::string name; // uses vertex_from_name<vertex_info>
vertex_info(const std::string &name_) : name(name_) { }
};
ostream& operator<<(ostream & os, const vertex_info &v)
{
os << v.name;
return os;
}
namespace boost { namespace graph {
template<typename Type>
struct vertex_name_extractor
{
typedef Type type;
typedef const std::string& result_type;
result_type operator()(const Type& v) const
{
return v.name;
}
};
template<>
struct internal_vertex_name<vertex_info>
{
typedef vertex_name_extractor<vertex_info> type;
};
template<>
struct internal_vertex_constructor<vertex_info>
{
typedef vertex_from_name<vertex_info> type;
};
} }
typedef adjacency_list< vecS, vecS, undirectedS, vertex_info, edge_info> graph_t;
namespace bg=boost::graph;
int main()
{
using namespace std;
graph_t g;
int i;
typedef graph_traits<graph_t>::vertex_descriptor vert;
for(i=0;i < 10;++i)
{
开发者_开发百科string t_name("Vertex");
vert V;
t_name += lexical_cast<string>(i);
V = add_vertex(t_name,g);
}
typedef graph_t::vertex_name_type name_t;
name_t s_temp("Vertex2");
optional<vert> V(
find_vertex(s_temp,g));
if( V ) {
cout << "Found vertex:" << *V << '\n';
//remove_vertex(*V,g); // (1)
//remove_vertex(vertex(*V,g),g); // (2)
//remove_vertex(g[*V],g); // (3)
//remove_vertex(s_temp,g); // (4)
} else {
cout << "Vertex not found\n";
}
graph_traits<graph_t>::vertex_iterator v_i, v_end;
for(tie(v_i,v_end) = vertices(g); v_i != v_end; ++v_i)
{
cout << '\'' << g[*v_i] << '\'' << endl;;
}
}
When I try using (3) or (4), I get an error for no matching function call to ‘remove_vertex(vertex_info&, graph_t&)’
adjacency_list.hpp:2211 candidates: remove_vertex(typename graph_t::vertex_descriptor, graph_t &)
But when I try using (1) or (2), I get an error for invalid conversion from ‘long unsigned int’ to ‘const char*’.
error: initializing argument 1 of ‘std::basic_string<...'
boost/graph/named_graph.hpp:349
template<BGL_NAMED_GRAPH_PARAMS>
inline void BGL_NAMED_GRAPH::removing_vertex(Vertex vertex)
{
named_vertices.erase(vertex); //line 349
}
vertex_name extractor's result_type should have const and reference qualifiers removed. The function object should specify that it returns a const reference. This allows for proper meta-functions that rely on result_type without removing them. Overloaded functors can be specified easier.
template<typename Type>
struct vertex_name_extractor
{
typedef Type type;
typedef std::string result_type;
const result_type& operator()(const Type& v) const
{
return v.name;
}
} ;
The creating a bundled VertexProperty can be extended easier if we specify our own constructor.
template<typename VertexProperty>
struct vertex_info_constructor
{
typedef VertexProperty return_type;
typedef typename vertex_name_extractor<VertexProperty>::result_type argument_type;
return_type operator()(argument_type n)
{
VertexProperty v(n);
return v;
}
};
template<>
struct internal_vertex_constructor<vertex_info>
{
typedef vertex_info_constructor<vertex_info> type;
};
adjacency_list uses MI mixin, with its base class maybe_named_graph<>. Following the example for turning off named_graphs when the internal_vertex_name::type is void, I added a partial specialization of maybe_name_graph::type > as follows:
template<typename Graph, typename Vertex>
struct maybe_named_graph<Graph, Vertex, vertex_info, vertex_name_extractor<vertex_info> >
: public named_graph<Graph, Vertex, vertex_info>
{
typedef named_graph<Graph, Vertex, vertex_info> Base;
//maybe_named_graph() { }
typedef typename detail::extract_bundled_vertex<vertex_info>::type
bundled_vertex_property_type;
void added_vertex(Vertex v) { Base::added_vertex(v); }
void removing_vertex(Vertex v) {
const std::string &name = extract_name((Base::derived()[v]));
Base::named_vertices.erase(name);
}
void clearing_graph() { Base::clearing_graph(); }
optional<Vertex>
vertex_by_property(const bundled_vertex_property_type& t)
{
return Base::vertex_by_property(t);
}
};
Now adjacency_list's remove_vertex( VertexDescriptor, Graph ) calls my specialized removing_node that removes from the vertex_name from the named_graph by vertex descriptor.
note: vecS is used, so you still have to be careful with iterator invalidation.
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