This is to practice tail recursion by creating a method that splits text after 80 characters long and adds the next line over. split80(...) works but it is not tail recursive. newSplit80(...) attempts that.

rec.scala

/**
 * Recursive split text to lines of 80 characters
 */
def split80(text: String): String = {
  if (text.length <= 80) {
    text
  } else {
    text.substring(0, 80) + "\n" + split80(text.substring(80))
  }
}

/**
 * Recursive split text to lines of 80 characters
 */
def newSplit80(text: String): String = {
  def loop(acc: String, line: String): String = {
    if (acc.length <= 80) 
      acc
    else 
      loop(acc.substring(80), acc + line)
  }
  loop(text, "\n")
}