README

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In reference to a post comparing programming languages.

I did two versions, the first one is closer to the original, the second one is more efficient and nicer IMHO.

I have been thinking about choosing "the best programming language" for a while, for a number of reasons, including long term DRY.

1HofstadterQseqIdiomatic.scala

// Idiomatic version

object HofstadterQseqIdiomatic extends App {
  def q(n: Int): Int =
    if (n <= 2) 1
    else q(n - q(n - 1)) + q(n - q(n - 2))
  def linePrint(index: Int, value: Int) = println(s"Q($index) = $value")
  (1 to 10) map { i => (i, q(i)) } foreach (linePrint _).tupled
  linePrint(1000, q(1000))
}

2HofstadterQseqEfficient.scala

// Idiomatic and efficient version

object HofstadterQseqEfficient extends App {
  val q: Stream[Int] = 1 #:: 1 #:: 1 #:: (3 to Int.MaxValue).iterator.map { n =>
    q(n - q(n - 1)) + q(n - q(n - 2))
  }.toStream
  (1 to 10) foreach { i => println(s"Q($i) = ${q(i)}") }
  println(s"Q(1000) = ${q(1000)}")
}