go =>
  % removing '\n' first
  Chars = delete_all(read_file_chars("unixdict.txt"),'\n'),
  M = letter_freq(Chars),
  println(M.sort_map(values).reverse).

% Get the letter frequency
letter_freq(S) = Map =>
  Map = new_map(),
  foreach(C in S)
    Map.put(C,Map.get(C,0)+1)
  end.

% Different sorting function on maps
sort_map(Map,values) = [K=V:_=(K=V) in sort([V=(K=V): K=V in Map])].
sort_map(Map,keys)   = sort([KV : KV in Map]).
sort_map(Map)        = sort_map(Map,keys).