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listscalaindexingreplace

replacing efficiently an element of a list in the same index with other a sub elements Scala

I want to add other elements to a list in the index of a given item. for instance

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

I want to replace the element 3 with (3, 7) which will gives this output

val list = List(1,2,3,7,4)

in an efficient and generic way

here is what I tried

list.zipWithIndex.map { case (item, index) =>
if(item == 3) {
  list.updated(index, List(item ,7))
} else list

but this is not working and its not efficient in case of traversing a long list

Solution 
  • list.take(index) ++ List(7) ++ list.drop(index)

    See answer linked in comments for more efficient version using splitAt