Find and Replace item in Scala collection

问题

Let's say I have a list:

val list = List(1,2,3,4,5)

I want to replace all/first items that satisfy a predicate, I know the following way to do it: (e.g. replace any number that is even with -1)

val filteredList = list.zipWithIndex.filter(_._2 % 2 == 0)
val onlyFirst = list.updated(filteredList.head._2, -1)
val all = for(i <- list) yield if(i % 2 ==0) -1 else i

Is there any collection function or nice Scala way that helps in this situation and has a good performance?

I also want to keep the order, so I don't want to use filterNot and add other items to the list like: (it's also not efficient)

val onlyFirst = list.filterNot(_ % 2 != 0) ::: list.filter(_ % 2 == 0).map(x => -1)

回答1:

Simple & efficient: Replace all items

list.map( x => if (x % 2 == 0) -1 else x )

Replace one item

val index = list.indexWhere( _ % 2 == 0 )
list.updated(index, -1)

来源：https://stackoverflow.com/questions/33788185/find-and-replace-item-in-scala-collection