An implementation of creating a Christmas tree. The idea was to try to create a solution by composing reusable functions as an alternative to the example here http://sortega.github.io/programming/2013/07/06/functional-tree/

Trees.scala

object Trees extends App {

  def zero = '0'

  def repeat(c: Char)(n: Int) = c.toString * n

  def reflect(centre: Char)(s: String) = s.reverse + centre + s

  def pad(w: Int, c: Char)(s: String) = s.padTo(w - 1, c)

  def line(w: Int, centre: Char)(n: Int) = repeat(zero) _ andThen pad(w, ' ') _ andThen reflect(centre) _ apply (n)

  def star(w: Int) = Seq(line(w, '*')(0))

  def apply(w: Int): Seq[String] = star(w) ++ Seq.tabulate(w)(line(w, zero))
}