// returns comments

static LS gazelle_proposeCalculationFunctions(S ruleText, ai_gazelle_analyzeStatementsForRule_Data data) {

  PairS rule = splitAtDoubleArrow_pair(ruleText);

  S var1 = firstIntAsString(rule.a), var2 = secondIntAsString(rule.a);

  S var3 = firstIntAsString(rule.b);

  if (var1 == null || var2 == null || var3 == null) ret emptyList();

  LS functions = ai_numberCalculationFunctions();

  for (SS map : listPlus(data.completeGoodMappings, null)) {

    if (empty(functions)) null;

    L<Double> numbers = ll(parseDouble(getOrKeep(map, var1)),

      parseDouble(getOrKeep(map, var2)));

    double result = parseDouble(getOrKeep(map, var3));

    print("Checking map: " + map + " - " + numbers + " -> " + result);

    functions = filter(functions, func(S f) -> bool {

      ai_checkNumberCalculationFunction1(f,

        numbers,

        result)

    });

    print("Remaining functions: " + functions);

  }

  ret ll(format("compute var " + quote(var3) + " from " + quote(var1) + " and " + quote(var2) + " using *", first(functions)));

}