Merge pull request #148 from akrzemi1/example

Example on how to adapt your own graph structure

Author: pratzl

example/AdaptingThirdPartyGraph/CMakeLists.txt

@@ -0,0 +1,12 @@
+# example/AdaptingThirdPartyGraph/CMakeLists.txt
+
+set(EXAMPLE_OUTPUT_DIR "${CMAKE_CURRENT_SOURCE_DIR}/output/")
+add_compile_definitions(EXAMPLE_OUTPUT_DIR="${EXAMPLE_OUTPUT_DIR}")
+
+#add_library(catch_main STATIC catch_main.cpp)
+#target_link_libraries(catch_main PUBLIC Catch2::Catch2)
+#target_link_libraries(catch_main PRIVATE project_options)
+#target_link_options(catch_main INTERFACE $<$<CXX_COMPILER_ID:GNU>:-pthread -fconcepts-diagnostics-depth=1>)
+
+add_executable(AdaptingThirdPartyGraph  "adapting_a_third_party_graph.cpp")
+target_link_libraries(AdaptingThirdPartyGraph PRIVATE project_warnings project_options catch_main Catch2::Catch2WithMain graph)

example/AdaptingThirdPartyGraph/adapting_a_third_party_graph.cpp

@@ -0,0 +1,89 @@
+// Copyright (C) 2025 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// This test file demonstrates how one can adapt one's own graph container for use with 
+// this Graph Library
+
+#include <graph/views/depth_first_search.hpp>
+#include <graph/graph.hpp>
+#include <string>
+#include <vector>
+#include <iostream>
+
+
+namespace MyLibrary 
+{                     // custom graph container, conceptually an adjacency list
+
+struct MyEdge
+{
+   std::string content;
+   int indexOfTarget;
+};
+
+struct MyVertex
+{
+    std::string content;
+    std::vector<MyEdge> outEdges;
+};
+
+class MyGraph 
+{
+    std::vector<MyVertex> _vertices;
+public:
+    MyVertex const* getVertexByIndex(int index) const 
+    { return &_vertices[static_cast<unsigned>(index)]; }
+    
+    std::vector<MyVertex> const& getAllVertices() const // !! one of customization points
+    { return _vertices; }                               //    forced me to add this fun
+    
+    void setTopology(std::vector<MyVertex> t) { _vertices = std::move(t); }
+};
+
+}
+
+namespace MyLibrary 
+{                     // customization for graph, unintrusive
+                      // although forcing me to provide `vertices()` is superfluous
+
+auto vertices(MyGraph const& g) 
+{ return std::views::all(g.getAllVertices()); } // for vertex_range_t
+
+auto edges(MyGraph const&, const MyLibrary::MyVertex& v) 
+{ return std::views::all(v.outEdges); }
+
+auto edges(MyGraph const& g, int i) 
+{ return edges(g, *g.getVertexByIndex(i)); }
+
+int vertex_id(MyGraph const& g, std::vector<MyVertex>::const_iterator it) 
+{ return static_cast<int>(std::distance(g.getAllVertices().begin(), it)); }
+
+int target_id(MyGraph const&, MyEdge const& uv) 
+{ return uv.indexOfTarget; }
+
+}
+
+
+int main()
+{
+    static_assert(graph::adjacency_list<MyLibrary::MyGraph>);
+  
+    const MyLibrary::MyGraph g = [] {             // populate the graph
+        MyLibrary::MyGraph r;
+        std::vector<MyLibrary::MyVertex> topo {   //         A       |
+            /*0*/ {"A", {{"", 1}, {"", 2}}},      //       /  \      | 
+            /*1*/ {"B", {{"", 3}}},               //      B    C     |
+            /*2*/ {"C", {{"", 3}}},               //       \  /      |
+            /*3*/ {"D", {}}                       //        D        |
+        };
+        r.setTopology(std::move(topo));
+        return r;
+    }();
+
+    for (auto const& [vid, v]  : graph::views::vertices_depth_first_search(g, 0))
+        std::cout << v.content << " ";
+    
+    std::cout << std::endl;
+}

example/CMakeLists.txt

@@ -2,3 +2,4 @@
 
 add_subdirectory(CppCon2021)
 add_subdirectory(CppCon2022)
+add_subdirectory(AdaptingThirdPartyGraph)