Scala：SeqT monad 转换器？

Question

如果我们有这样两个函数...

def findUserById(id: Long): Future[Option[User]] = ???
def findAddressByUser(user: User): Future[Option[Address]] = ???

...然后我们就可以使用 cats OptionT monad transformer 轻松地编写用于理解的内容：

for {
  user    <- OptionT(findUserById(id))
  address <- OptionT(findAddressByUser(user))
} ...

我想用这种方式组合未来的序列，像这样：

def findUsersBySomeField(value: FieldValue): Future[Seq[User]] = ???
def findAddressesByUser(user: User): Future[Seq[Address]] = ???

for {
  user    <- SeqT(findUsersBySomeField(value))
  address <- SeqT(findAddressesByUser(user))
} ...

但我在 Cats 或 Scalaz 中找不到任何 SeqT 实现。是否存在此类 monad 转换器的某些实现，或者我需要自己编写 monad 转换器？不是太难，只是不想重新发明轮子

（我问题开头的例子来自this article）

Answer 1

猫，从 1.0.0-MF 开始就没有了。在 their FAQ:

中有解释

A naive implementation of ListT suffers from associativity issues; see this gist for an example. It's possible to create a ListT that doesn't have these issues, but it tends to be pretty inefficient. For many use-cases, Nested can be used to achieve the desired results.

Scalaz，截至 7.2.15 有 StreamT 和 ListT，尽管后者 has 关联性问题。

Scala：SeqT monad 转换器？

Scala: SeqT monad transformer?

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