type
  Pos = range[1'i16 .. high(int16)]
  Node = ref object
    word: string
    freq: Natural
    places: set[Pos]
    le, ri: Node
  Bst* = object
    root: Node

proc search(curr: Node, word: string): (Natural, set[Pos]) =
  if curr == nil:
    (0.Natural, {})
  elif word < curr.word:
    search(curr.le, word)
  elif word > curr.word:
    search(curr.ri, word)
  else:
    (curr.freq, curr.places)