Merge pull request #6158 from johnfxgalea/add-get-predecessors

Adds get_predecessors() to grapht

Author: tautschnig

src/util/graph.h

@@ -312,6 +312,7 @@ class grapht
 
   std::list<node_indext> topsort() const;
 
+  std::vector<node_indext> get_predecessors(const node_indext &n) const;
   std::vector<node_indext> get_successors(const node_indext &n) const;
   void output_dot(std::ostream &out) const;
   void for_each_successor(
@@ -934,6 +935,19 @@ void output_dot_generic(
   });
 }
 
+template <class N>
+std::vector<typename grapht<N>::node_indext>
+grapht<N>::get_predecessors(const node_indext &n) const
+{
+  std::vector<node_indext> result;
+  std::transform(
+    nodes[n].in.begin(),
+    nodes[n].in.end(),
+    std::back_inserter(result),
+    [&](const std::pair<node_indext, edget> &edge) { return edge.first; });
+  return result;
+}
+
 template <class N>
 std::vector<typename grapht<N>::node_indext>
 grapht<N>::get_successors(const node_indext &n) const

unit/util/graph.cpp

@@ -310,3 +310,25 @@ SCENARIO("graph-connected-subgraphs",
     }
   }
 }
+
+SCENARIO("predecessors-successors-graph", "[core][util][graph]")
+{
+  GIVEN("A graph")
+  {
+    simple_grapht graph;
+    simple_grapht::node_indext indices[2];
+
+    for(int i = 0; i < 2; ++i)
+      indices[i] = graph.add_node();
+
+    graph.add_edge(indices[0], indices[1]);
+
+    THEN("Nodes should have correct successors and predecessors")
+    {
+      REQUIRE(graph.get_predecessors(indices[0]).size() == 0);
+      REQUIRE(graph.get_successors(indices[0]).size() == 1);
+      REQUIRE(graph.get_predecessors(indices[1]).size() == 1);
+      REQUIRE(graph.get_successors(indices[1]).size() == 0);
+    }
+  }
+}