+// Search for a context of the given type starting from the given context and
+// moving toward the root of the tree. If the starting context matches, it is
+// returned.
+Context *find_context_above (Context *where, SCM type_sym);
+
+// Search for a context of the given type starting from the given context and
+// moving toward the root of the tree. If found, return its child that was
+// found on the way there.
+Context *find_context_above_by_parent_type (Context *where, SCM parent_type);
+
+// Search for a context of the given type and ID starting from the given
+// context and moving toward the leaves of the tree. If the starting context
+// matches, it is returned. An empty ID matches any context of the given type.