Tag: scala option

types不匹配在斯卡拉理解

为什么这个构造在Scala中导致types不匹配错误？ for (first <- Some(1); second <- List(1,2,3)) yield (first,second) <console>:6: error: type mismatch; found : List[(Int, Int)] required: Option[?] for (first <- Some(1); second <- List(1,2,3)) yield (first,second) 如果我切换列表它编译罚款： for (first <- List(1,2,3); second <- Some(1)) yield (first,second) res41: List[(Int, Int)] = List((1,1), (2,1), (3,1)) 这也工作正常： for (first <- Some(1); second <- Some(2)) yield […]