Better functional implementation of excel-style column name generation in Scala https://blog.jooq.org/2015/12/08/3-reasons-why-you-shouldnt-replace-your-for-loops-by-stream-foreach/

nthColumnLabel.scala

// Using new collection library in Scala 2.13 
def nthColumnLabel(n: Int): String =
  Iterator
    .unfold(n) {
      case 0 => None
      case m =>
        val m2 = m - 1
        Some((m2 % 26 + 'A').toChar, m2 / 26)
    }
    .mkString
    .reverse

// Using tail recursion
def nthColumnLabel2(n: Int): String = {
  @annotation.tailrec
  def iter(acc: List[Char], m: Int): String =
    m - 1 match {
      case -1 => acc.mkString
      case m2 =>
        iter((m2 % 26 + 'A').toChar :: acc, m2 / 26)
    }
  iter(Nil, n)
}

println(
  (1 to 32)
    .map(nthColumnLabel)
    .mkString(", ")
)
// A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, AA, AB, AC, AD, AE, AF