query method

Implementation

@override
Iterable<Node> query(Database database) {
  Iterable<Node> solutions(int index, Map<Variable, Node> bindings) sync* {
    if (index < arguments.length) {
      final arg = arguments[index];
      final subs = arg.substitute(bindings) as Term;
      for (final item in database.query(subs)) {
        final unified = mergeBindings(arg.match(item), bindings);
        if (unified != null) {
          yield* solutions(index + 1, unified);
        }
      }
    } else {
      yield substitute(bindings);
    }
  }

  return solutions(0, newBindings());
}