sS ai_ruleOfThree_solver_2(S db, S input) {
  ret too_transformInput(input, too -> {
    too.addAll(lambdaMap(s -> Input(s), tlft(db)));

    too.addTransformer(func(Input<S> i) {
      BasicLogicRule<S> r = ai_parseIfThen(i!);
      if (r != null)
        too.addTransformer(func(Input<S> i2) {
          if (match(r.lhs, i2!))
            ret new TransformedInput(r.rhs);
          null;
        });
      null;
    });
  });
}

Began life as a copy of #1028827