Possible problem with order of parameters for one of the mappedReduced() calls

template <typename ResultType, typename Iterator, typename MapFunctor, typename ReduceFunctor>
QFuture<ResultType> mappedReduced(Iterator begin,
                                  Iterator end,
                                  MapFunctor map,
                                  ReduceFunctor reduce,
                                  ReduceOptions options = ReduceOptions(UnorderedReduce | SequentialReduce))
{
    return startMappedReduced<ResultType, typename MapFunctor::result_type>
    (begin, end, map, reduce, options);
}

return startMappedReduced<ResultType, typename MapFunctor::result_type>