我有两个函数返回Futures。我试图使用for-yield理解将第一个函数的修改结果提供给另一个。 这种方法的工作原理: val schoolFuture = for {
ud <- userStore.getUserDetails(user.userId)
sid = ud.right.toOption.flatMap(_.schoolId)
s <- schoo
我有以下程序:(斯卡拉2.9.2的Java6) object Forcomp {
def main(args: Array[String]): Unit = {
val xs = List(-1, 0, 1)
val xss = for (a <- xs; b <- xs if a != 0 && b != 0) yield (a,b)
println(xs
下一个代码 def f(chars: List[Char]): List[List[Char]] = chars match {
case Nil => List(Nil)
case x :: xs => for {
v <- f(xs)
} yield List(x) :: v
}
提供错误消息 - type mismatch; found
我正在阅读通过Scala for the Impatient,我遇到了一些让我挠头的东西。 下返回一个字符串: scala> for (c<-"Hello"; i <- 0 to 1) yield (c+i).toChar
res68: String = HIeflmlmop
但这返回向量: scala> for (i <- 0 to 1; c <- "Hello") yield (c +