using tensor product in scala

I just tried this code:

sealed trait Result[+T] {
...
  def <*>[U](other: Result[U]): Result[(T,U)]
...
}
case class Good[T](value:T) extends Result[T] {
...
  def <*>[U](other: Result[U]): Result[(T, U)] = other.flatMap(u => Good((value, u)))
...
}

case class Bad[T](errors:Traversable...) extends Result[T] {
...
  def <*>[U](other: Result[U]): Result[(T, U)] = Bad(errors ++ other.errors)
...
}

scala> val op = Good((1,"one"))
op: Good[(Int, String)] = Good((1,one))

scala> for ((i,s) <- op) println(s"i=$i, s=$s")
i=1, s=one

Why is this important?

See, if I have a class Result[T], and it is applicative, so Result[T] <*> Result[U] produces Result[(T,U)], I want to use the result, naming individual fields. Like in

  val username: Result[String] = getUserNameFromTheCloud(userId)
  val prize:  Result[Prize] = rollTheDice
  
  val letter:Result[(String, Prize)] = for ((u, p) <- username <*> prize) yield congratulate(u, p)
// etc

This is better than having

for(u <- username;
    p <- prize) yield congratulate(u,p)

because in the second case if username is bad, we will never know if prize is bad too; this way we detect only one error. Not so good for fast development. It's like what ancient compilers did.

Questions?

a style/monads question

I have this code:

  lazy val eobOpt: Result[EOB] = ...
  ...

  def items: Result[Traversable[EOB_item]] = {
    val listOfParsedItems: Traversable[Result[EOB_item]] =
      itemsData map {
        item => {
          eobOpt flatMap (buildItem(_)(item))
        }
      }
    Result.traverse(listOfParsedItems).map(_.toList)
  }

Something does not look nice here. flatMap, should not have an alias name, like =>> or something? I can juggle things around, but what I'm looking for is simple beauty, or beautiful simplicity, same thing.

an update

Я тут на днях постил картинку с "хаком от Олега Плисса".

Короче, мне разъяснили забаненные собеседники, что
а) да он матмех закончил, а не какой-то там физфак.
Good for him. Кафедра Матобеспечения, не хуй собачий. (По мне так там э... чему конкретно там учили-то?)
б) Да он вообще, оказывается, живет где-то тут в Санта Кларе и работает в Оракле.

в) и чо?

Ну вы поняли, это обычные питерские разборки, типа кто тут у нас крутой и ваще.

МНЕ ПОФИГ

Але, Куздра, ну я запостил дисклеймер, давай до свидания.

big monad

so, say, we blend List (or Set, or Traversable Once) and Result (or Option, or Either), and define proper monadic multiplication.

For immutables, it will be it, right? No? Of course, for parallel stuff there's continuation, and future; for mutables, it will be state continuation, as Oleg said.

But for this specific small Kleisli category, is not it enough?

Just asking.