// 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 : data.completeGoodMappings) {
    if (empty(functions)) null;
    functions = filter(functions, func(S f) -> bool {
      ai_checkNumberCalculationFunction1(f,
        ll(parseDouble(getOrKeep(map, var1)),
          parseDouble(getOrKeep(map, var2))),
        parseDouble(getOrKeep(map, var3)))
    });
    print("Remaining functions: " + functions);
  }
  
  ret ll(format("compute var " + quote(outVar) + " from " + var1 + " and " + var2 + " using *", first(functions)));
}