为什么以下函数不是尾递归？

如thefourtheye所述,您的函数返回folds 的结果.尾递归版(带模式匹配)看起来像:

@tailrec
def loop(newInterests: Set[Interest], oldInterests: Set[Interest]): Set[Interest] = {
  newInterests.headOption match {
    case None => oldInterests
    case Some(ni) =>
      oldInterests.find(oi => oi.keyword == ni.keyword) match {
        case None => loop(newInterests.tail, oldInterests + ni)
        case Some(k) => loop(newInterests.tail, oldInterests - k + k.copy(count = k.count + 1))
      }
  }
}