c++ - 使用 Boost,如何将自定义边缘属性作为结构放置/获取?
问题描述
我已经在这里阅读了文档(https://www.boost.org/doc/libs/1_75_0/libs/graph/doc/using_adjacency_list.html)和几个堆栈溢出页面两个小时,但没有取得任何进展在这里。我有一个图表,其中边缘既有距离又有坑洞的数量(撞到 3 个坑洞后车辆中断),所以我想我会使用自定义结构并设置边缘属性。
将其放在类声明之上:
struct road_details_t {
typedef boost::edge_property_tag kind;
};
struct road_info {
unsigned miles;
bool pothole;
};
typedef boost::property<road_details_t, struct road_info> RoadDetailsProperty;
编辑:我相信这是上述方法的替代方案,也没有运气:
namespace boost {
enum road_details_t { road_details };
BOOST_INSTALL_PROPERTY(edge, road_details);
}
类声明中的邻接图:
typedef boost::adjacency_list<boost::listS, // store edges in lists
boost::vecS, // store vertices in a vector
boost::undirectedS
RoadDetailsProperty
>
Graph;
typedef boost::graph_traits<Graph> GraphTraits;
typedef GraphTraits::vertex_descriptor Vertex;
typedef GraphTraits::edge_descriptor Edge;
Graph roadMap;
稍后在添加道路的功能中:
void City::addRoad(Intersection intersection1, Intersection intersection2, unsigned time, bool pothole)
{
unsigned nV = num_vertices(roadMap);
while (intersection1 >= nV)
nV = add_vertex(roadMap)+1;
while (intersection2 >= nV)
nV = add_vertex(roadMap)+1;
add_edge(intersection1, intersection2, roadMap);
所以现在我正在尝试输入/获取道路信息,其中有多个错误,并且我尝试了很多变化:
// get the edge
std::pair<Edge, bool> edg = edge(intersection1, intersection2, roadMap);
// get the property map for road details. ERROR: no matching function call to get()
typename property_map<Graph, road_details_t>::type
roadDetailMap = get(road_details_t(), roadMap);
// create struct from arguments passed in
struct road_info info = {time, pothole};
// attempt to add to roadDetailMap
put(roadDetailMap, edg, info);
// roadDetailMap[edg] = info; // also not working
// attempt to fetch information
cout << get(roadDetailMap, edg).miles << endl;
// cout << roadDetailMap[edg].miles << endl; // also not working
通过注释掉不同的行,我发现问题似乎在于我如何获取属性图,但是在网上查看示例时,我觉得我正在做与他们完全相同的事情。
目标最终只是弄清楚如何添加道路信息以及以后如何获取它,因此可以接受完全不同的方法,我在这里所拥有的只是我尝试过的(不成功)但我觉得最多的有希望的结果。
解决方案
您可以按照您的建议进行操作,这需要使用注册属性标签BOOST_INSTALL_PROPERTY
(参见example/examples/edge_property.cpp 以获取示例)。相关片段:
namespace boost { enum edge_flow_t { edge_flow }; enum edge_capacity_t { edge_capacity }; BOOST_INSTALL_PROPERTY(edge, flow); BOOST_INSTALL_PROPERTY(edge, capacity); }
现在,您可以在属性定义中使用新的属性标记,就像使用内置标记之一一样。
typedef property<capacity_t, int> Cap; typedef property<flow_t, int, Cap> EdgeProperty; typedef adjacency_list<vecS, vecS, no_property, EdgeProperty> Graph;
vertex_bundle_t
但是,由于您的用例如此频繁,因此任何用户定义的 struct:和都已经有一个内置标记edge_bundle_t
:
捆绑属性
这是一个使用它的示例。文档:https ://www.boost.org/doc/libs/1_75_0/libs/graph/doc/bundles.html
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graph_utility.hpp>
struct road_info {
unsigned miles;
bool pothole;
};
using Graph = boost::adjacency_list<boost::listS, boost::vecS,
boost::undirectedS, road_info>;
using Vertex = Graph::vertex_descriptor;
using Edge = Graph::edge_descriptor;
int main() {
Graph roadMap;
Vertex road1 = add_vertex(road_info{15, false}, roadMap);
Vertex road2 = add_vertex(road_info{3, true}, roadMap);
/*Vertex road3 =*/ add_vertex(road_info{27, false}, roadMap);
add_edge(road1, road2, roadMap);
print_graph(roadMap);
auto bmap = get(boost::vertex_bundle, roadMap);
for (Vertex v : boost::make_iterator_range(vertices(roadMap))) {
road_info& bundle = bmap[v];
// or even easier
// road_info& info = roadMap[v];
auto& [miles, pothole] = roadMap[v]; // c++17
std::cout << "Vertex #" << v << " " << miles << " miles, "
<< "pothole:" << std::boolalpha << pothole << "\n";
}
// individual maps
auto miles_map = get(&road_info::miles, roadMap);
auto poth_map = get(&road_info::pothole, roadMap);
for (Vertex v : boost::make_iterator_range(vertices(roadMap))) {
std::cout << "Vertex #" << v << " " << miles_map[v] << " miles, "
<< "pothole:" << std::boolalpha << poth_map[v] << "\n";
put(poth_map, v, false); // reset pothole
}
}
印刷
0 <--> 1
1 <--> 0
2 <-->
Vertex #0 15 miles, pothole:false
Vertex #1 3 miles, pothole:true
Vertex #2 27 miles, pothole:false
Vertex #0 15 miles, pothole:false
Vertex #1 3 miles, pothole:true
Vertex #2 27 miles, pothole:false
更新:边缘捆绑
对于评论,使其成为边缘捆绑是肤浅的修改:
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graph_utility.hpp>
struct road_info {
unsigned miles;
bool pothole;
};
using Graph =
boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS,
boost::no_property, road_info>;
using Vertex = Graph::vertex_descriptor;
using Edge = Graph::edge_descriptor;
int main() {
Graph roadMap(3);
add_edge(0, 1, road_info{15, false}, roadMap);
add_edge(1, 2, road_info{3, true}, roadMap);
print_graph(roadMap);
auto bmap = get(boost::edge_bundle, roadMap);
for (Edge e : boost::make_iterator_range(edges(roadMap))) {
road_info& bundle = bmap[e];
// or even easier
// road_info& info = roadMap[e];
auto& [miles, pothole] = roadMap[e]; // c++17
std::cout << "Edge " << e << " " << miles << " miles, "
<< "pothole:" << std::boolalpha << pothole << "\n";
}
// individual maps
auto miles_map = get(&road_info::miles, roadMap);
auto poth_map = get(&road_info::pothole, roadMap);
for (Edge e : boost::make_iterator_range(edges(roadMap))) {
std::cout << "Edge " << e << " " << miles_map[e] << " miles, "
<< "pothole:" << std::boolalpha << poth_map[e] << "\n";
put(poth_map, e, false); // reset pothole
}
}
印刷:
0 <--> 1
1 <--> 0 2
2 <--> 1
Edge (0,1) 15 miles, pothole:false
Edge (1,2) 3 miles, pothole:true
Edge (0,1) 15 miles, pothole:false
Edge (1,2) 3 miles, pothole:true
对于受虐狂
如果您坚持,您当然可以安装属性标签。接触个别成员会很不舒服(并且可能效率低下),但你这样做:
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graph_utility.hpp>
#include <boost/property_map/transform_value_property_map.hpp>
struct road_info {
unsigned miles;
bool pothole;
};
namespace boost {
struct edge_road_info_t {};
BOOST_INSTALL_PROPERTY(edge, road_info);
static inline constexpr edge_road_info_t road_info{};
}
using Graph =
boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS,
boost::no_property,
boost::property<boost::edge_road_info_t, road_info> >;
using Vertex = Graph::vertex_descriptor;
using Edge = Graph::edge_descriptor;
int main() {
Graph roadMap(3);
add_edge(0, 1, road_info{15, false}, roadMap);
add_edge(1, 2, road_info{3, true}, roadMap);
print_graph(roadMap);
auto info_map = get(boost::road_info, roadMap);
for (Edge e : boost::make_iterator_range(edges(roadMap))) {
road_info& info = info_map[e];
// or even easier
// road_info& info = roadMap[e];
auto& [miles, pothole] = info; // c++17
std::cout << "Edge " << e << " " << miles << " miles, "
<< "pothole:" << std::boolalpha << pothole << "\n";
}
// individual maps
auto miles_map = boost::make_transform_value_property_map(
std::mem_fn(&road_info::miles), info_map);
auto poth_map = boost::make_transform_value_property_map(
std::mem_fn(&road_info::pothole), info_map);
for (Edge e : boost::make_iterator_range(edges(roadMap))) {
std::cout << "Edge " << e << " " << miles_map[e] << " miles, "
<< "pothole:" << std::boolalpha << poth_map[e] << "\n";
put(poth_map, e, false); // reset pothole
}
}
再次打印相同的输出。
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