void add_child(Predicate * child);
void set_parent(Predicate * parent_pred) { parent = parent_pred; }
void set_backedge(Predicate * back_pred) { backedge = back_pred; }
void add_child(Predicate * child);
void set_parent(Predicate * parent_pred) { parent = parent_pred; }
void set_backedge(Predicate * back_pred) { backedge = back_pred; }