adding custom vertices to a boost graph

Question

If I have n elements defined with class CElement, how can one create vertices of those elements with boost graph - and connect them also? I've seen boost graph bundled props, but I just can't figure this one out.

sorry for not being clear. Instances of CElements are vertices. I'd like to be able to add, delete, connect and disconnect those instances of CElements. Do I really need to define struct Vertex which has pt to CElement instance or there is a more elegant way? — dodol, Jun 23 '10 at 09:04

score 59 · Accepted Answer · edited Apr 26 '20 at 07:53

59

I don't understand what you want to do exactly. Do you want to associate some data to vertices? Then use bundled properties.

//Define a class that has the data you want to associate to every vertex and edge
struct Vertex{ int foo;}
struct Edge{std::string blah;}

//Define the graph using those classes
typedef boost::adjacency_list<boost::listS, boost::vecS, boost::directedS, Vertex, Edge > Graph;
//Some typedefs for simplicity
typedef boost::graph_traits<Graph>::vertex_descriptor vertex_t;
typedef boost::graph_traits<Graph>::edge_descriptor edge_t;

//Instanciate a graph
Graph g;

// Create two vertices in that graph
vertex_t u = boost::add_vertex(g);
vertex_t v = boost::add_vertex(g);

// Create an edge conecting those two vertices
edge_t e; bool b;
boost::tie(e,b) = boost::add_edge(u,v,g);


// Set the properties of a vertex and the edge
g[u].foo = 42;
g[e].blah = "Hello world";

The are other ways to set the properties, but there you a have an example to bootstrap.

I hope I didn't misunderstand the question.

edited Apr 26 '20 at 07:53

Zoe

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answered Jun 23 '10 at 08:54

Tristram Gräbener

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I think that instead of edge_t e = boost::add_edge(u,v,g); one should write edge_t e; bool added; boost::tie(e,added) = boost::add_edge(u,v,g); – dodol Jun 23 '10 at 11:28
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@Tristram "easier than using bundled properties" -- what you've described in this answer exactly *IS* bundled properties. =) – wjl Jul 19 '13 at 14:35
Is there a way to dynamically create object edge(u,v) and lookup its bundled property? This would be done in a different function that doesn't have boost::tie(e,b) = boost::add_edge(u,v,g); available, only vertex indices. – Budric Apr 18 '16 at 18:29
is it possible gven my vertex data `int foo` to find the vertex descriptor which has already been added to the graph? – fferri Jan 20 '18 at 13:24

score 11 · Answer 2 · answered Mar 12 '18 at 10:15

Note that Boost.Graph has overloads which allow to simplify Tristram's answer:

#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graphviz.hpp>
#include <iostream>

int main()
{
    struct Vertex { int foo; };
    struct Edge { std::string blah; };

    using namespace boost;
    using graph_t  = adjacency_list<listS, vecS, directedS, Vertex, Edge >;
    using vertex_t = graph_traits<graph_t>::vertex_descriptor;
    using edge_t   = graph_traits<graph_t>::edge_descriptor;

    //Instantiate a graph
    graph_t g;

    // Create two vertices in that graph
    vertex_t u = boost::add_vertex(Vertex{123}, g);
    vertex_t v = boost::add_vertex(Vertex{456}, g);

    // Create an edge conecting those two vertices
    boost::add_edge(u, v, Edge{"Hello"}, g);

    boost::write_graphviz(std::cout, g, [&] (auto& out, auto v) {
       out << "[label=\"" << g[v].foo << "\"]";
      },
      [&] (auto& out, auto e) {
       out << "[label=\"" << g[e].blah << "\"]";
    });
    std::cout << std::flush;
}

Output:

digraph G {
0[label="123"];
1[label="456"];
0->1 [label="Hello"];
}

adding custom vertices to a boost graph

2 Answers2

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