Scala의 목록 또는 배열의 한 요소에만 함수 적용

tl; dr

import scala.collection.SeqLike
import scala.collection.generic.CanBuildFrom

implicit class Seq_[A, Repr, 
    S : ({type L[X] = X => SeqLike[A, Repr]})#L](seq: S) {

  def myApply[B >: A, That](f: A => B, ith: Int)
      (implicit bf: CanBuildFrom[Repr, B, That]): That =
    seq.updated(ith - 1, f(seq(ith - 1)))
}

토론

순진한 근사치 :

implicit class Seq_[A](seq: Seq[A]) {
  def myApply(f: A => A, ith: Int): Seq[A] =
    seq.updated(ith - 1, f(seq(ith - 1)))
}

사용 예 :

scala> (1 to 3).toList.myApply(_ + 10, ith = 2)
res: Seq[Int] = List(1, 12, 3)

시도한 실제 솔루션 :

implicit class Seq_[A, Repr <: SeqLike[A, Repr]](seq: Repr) {
  def myApply[B >: A, That](f: A => B, ith: Int)
                           (implicit bf: CanBuildFrom[Repr, B, That]): That =
    seq.updated(ith - 1, f(seq(ith - 1)))
}

불행히도 암시적인 것은 작동하지 않습니다. 이유를 잘 모르겠습니다.

scala> Seq_[Int, List[Int]]((1 to 3).toList).myApply(_ + 10, ith = 2)
res: List[Int] = List(1, 12, 3)

scala> Seq_[Int, List[Int]]((1 to 3).toList).myApply(_.toString + "*", ith = 2)
res: List[Any] = List(1, 2*, 3)

편집 : 수정했습니다!

implicit class Seq_[A, Repr](seq: SeqLike[A, Repr]) {
  def myApply[B >: A, That](f: A => B, ith: Int)
                           (implicit bf: CanBuildFrom[Repr, B, That]): That =
    seq.updated(ith - 1, f(seq(ith - 1)))
}

예:

scala> (1 to 3).toList.myApply(_ + 10, ith = 2)
res: List[Int] = List(1, 12, 3)

scala> (1 to 3).toVector.myApply(Math.pow(2, _), ith = 3)
res: scala.collection.immutable.Vector[AnyVal] = Vector(1, 2, 8.0)

하지만 난 그냥 당신은 또한에 대한 작업에 원하는 실현 Array되지 않습니다, SeqLike그래서 나를 좀 더 생각하자 ...

Ah, Predef has an implicit conversion from Array to ArrayOps, which is a subtype of SeqLike, so we just need to use a view bound.

implicit class Seq_[A, Repr <% SeqLike[A, Repr]](seq: Repr) {
  def myApply[B >: A, That](f: A => B, ith: Int)
                           (implicit bf: CanBuildFrom[Repr, B, That]): That =
    seq.updated(ith - 1, f(seq(ith - 1)))
}

And finally we have the right behavior:

scala> (1 to 3).toList.myApply(_ + 10, ith = 2)
res: List[Int] = List(1, 12, 3)

scala> (1 to 3).toArray.myApply(Math.pow(2, _), ith = 3)
res: Array[AnyVal] = Array(1, 2, 8.0)

Edit again - samthebest informs me that view bounds are deprecated, so using this guide we can replace it with a very ugly-looking context bound.

implicit class Seq_[A, Repr, 
    S : ({type L[X] = X => SeqLike[A, Repr]})#L](seq: S) {

  def myApply[B >: A, That](f: A => B, ith: Int)
      (implicit bf: CanBuildFrom[Repr, B, That]): That =
    seq.updated(ith - 1, f(seq(ith - 1)))
}