Chain.map seems not optimized

[jeongwoo-ji]

Current implementation of Chain.map is

final def map[B](f: A => B): Chain[B] =
  fromSeq(iterator.map(f).toVector)

Why it isn't implemented like this?

final def map[B](f: A => B): Chain[B] = this match {
  case Wrap(seq) => fromSeq(seq.map(f))
  case _         => fromSeq(iterator.map(f).toVector)
}

I think the problem is:

val x: List[Int] = List.fill(n)(0)
Chain.fromSeq(x).toList // takes O(1)
Chain.fromSeq(x)
  .map(identity) // takes O(n). its not a problem.
  .toList        // takes O(n)!! I think it could be O(1).

[kailuowang]

I agree that your optimization makes sense. Would you like to create a PR?

[gagandeepkalra]

I've just added PR for this issue.