Add useful functions to class_hierarchy_grapht

class_hierarchy_grapht is a more advanced representation of the class
hierarchy than class_hierarchyt. So ideally we want to migrate all
functions from the old version to the graph-based representation. This
commit does this for the functions get_parents_trans,
get_children_trans, and introduces a new function get_direct_children.

Author: antlechner

src/goto-programs/class_hierarchy.cpp

@@ -88,6 +88,65 @@ void class_hierarchy_grapht::populate(const symbol_tablet &symbol_table)
   }
 }
 
+/// Helper function that converts a vector of node_indext to a vector of ids
+/// that are stored in the corresponding nodes in the graph.
+class_hierarchy_grapht::idst
+class_hierarchy_grapht::ids_from_indices(const std::vector<node_indext>
+  &nodes) const
+{
+  idst result;
+  std::transform(
+    nodes.begin(),
+    nodes.end(),
+    back_inserter(result),
+    [&](const node_indext &node_index) {
+      return (*this)[node_index].class_identifier;
+    });
+  return result;
+}
+
+/// Get all the classes that directly (i.e. in one step) inherit from class c.
+/// \param c: The class to consider
+/// \return A list containing ids of all direct children of c.
+class_hierarchy_grapht::idst
+class_hierarchy_grapht::get_direct_children(const irep_idt &c) const
+{
+  const node_indext &node_index = nodes_by_name.at(c);
+  const auto &child_indices = get_successors(node_index);
+  return ids_from_indices(child_indices);
+}
+
+/// Helper function for `get_children_trans` and `get_parents_trans`
+class_hierarchy_grapht::idst
+class_hierarchy_grapht::get_reachable_ids(const irep_idt &c, bool forwards)
+const
+{
+  idst direct_child_ids;
+  const node_indext &node_index = nodes_by_name.at(c);
+  const auto &reachable_indices = get_reachable(node_index, forwards);
+  return ids_from_indices(reachable_indices);
+}
+
+/// Get all the classes that inherit (directly or indirectly) from class c.
+/// \param c: The class to consider
+/// \param [out] dest: A list containing ids of all classes that eventually
+///   inherit from c.
+class_hierarchy_grapht::idst
+class_hierarchy_grapht::get_children_trans(const irep_idt &c) const
+{
+  return get_reachable_ids(c, true);
+}
+
+
+/// Get all the classes that class c inherits from (directly or indirectly).
+/// \param c: The class to consider
+/// \param [out] dest: A list of class ids that c eventually inherits from.
+class_hierarchy_grapht::idst
+class_hierarchy_grapht::get_parents_trans(const irep_idt &c) const
+{
+  return get_reachable_ids(c, false);
+}
+
 void class_hierarchyt::get_children_trans_rec(
   const irep_idt &c,
   idst &dest) const
@@ -105,7 +164,7 @@ void class_hierarchyt::get_children_trans_rec(
     get_children_trans_rec(child, dest);
 }
 
-/// Get all the classes that inherit (directly or indirectly) from class c. The
+/// Get all the classes that class c inherits from (directly or indirectly). The
 /// first element(s) will be the immediate parents of c, though after this
 /// the order is all the parents of the first immediate parent
 /// \param c: The class to consider

src/goto-programs/class_hierarchy.h

@@ -89,6 +89,8 @@ class class_hierarchy_graph_nodet : public graph_nodet<empty_edget>
 class class_hierarchy_grapht : public grapht<class_hierarchy_graph_nodet>
 {
 public:
+  typedef std::vector<irep_idt> idst;
+
   /// Maps class identifiers onto node indices
   typedef std::unordered_map<irep_idt, node_indext> nodes_by_namet;
 
@@ -101,9 +103,19 @@ class class_hierarchy_grapht : public grapht<class_hierarchy_graph_nodet>
     return nodes_by_name;
   }
 
+  idst get_direct_children(const irep_idt &c) const;
+
+  idst get_children_trans(const irep_idt &c) const;
+
+  idst get_parents_trans(const irep_idt &c) const;
+
 private:
   /// Maps class identifiers onto node indices
   nodes_by_namet nodes_by_name;
+
+  idst ids_from_indices(const std::vector<node_indext> &nodes) const;
+
+  idst get_reachable_ids(const irep_idt &c, bool forwards) const;
 };
 
 /// Output the class hierarchy