remove first and last Element from scala.collection.immutable.Iterable[String]

Question

I am trying to convert my way of getting values from Form, but stuck some where

val os= for {
  m <- request.body.asFormUrlEncoded
  v <- m._2
} yield v

os is scala.collection.immutable.Iterable[String] and when i print it in console

os map println

console

sedet impntc
sun
job
03AHJ_VutoHGVhGL70

i want to remove the first and last element from it.

Solution 1

Use drop to remove from the front and dropRight to remove from the end.

def removeFirstAndLast[A](xs: Iterable[A]) = xs.drop(1).dropRight(1)

Example:

removeFirstAndLast(List("one", "two", "three", "four")) map println

Output:

two
three

Solution 2

Another way is to use slice.

val os: Iterable[String] = Iterable("a","b","c","d")
val result = os.slice(1, os.size - 1) // Iterable("b","c")

Comments

[MaxG]

although it looks good, isn't this answer problematic? It seems as if the list is being copied twice: 1. drop(1) copies the list without first element. 2. dropRight(1) copies it without the last element.

[Chris Martin]

@MaxG No, because drop on a linked list doesn't involve any copying.

[Xavier Guihot]

Note that if your Iterable has at least 2 elements, you could use init and tail to select respectively all elements except the last and all elements except the first: List("one", "two", "three", "four").init.tail