svoid dm_gazelle_newRuleDialog(S in) {
  dm_gazelle_newRuleDialog(in, in);
}

svoid dm_gazelle_newRuleDialog(S in, S out) {
  final JTextField tf1 = jtextfield(in);
  final JTextField tf2 = jtextfield(out);
  showFormTitled("Make a rule",
    "When", tf1,
    "Then", tf2,
    r {
      Pair<S, Bool> p = dm_gazelle_addRule(gtt(tf1), gtt(tf2));
      infoBox(p.b ? "Rule " + p.a + " added" : "Rule already there: " + p.a);
    });
}