/* 

  Letter frequency (Rosetta code) in Picat.

  http://rosettacode.org/wiki/Letter_frequency
  """
  Open a text file and count the occurrences of each letter.

  Some of these programs count all characters (including punctuation), 
  but some only count letters A to Z. 
  """

  This Picat model was created by Hakan Kjellerstrand, hakank@gmail.com
  See also my Picat page: http://www.hakank.org/picat/

*/


% import util.
% import cp.


main => go.


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

  % sort on values (much slower on large files)
  % println(sort_values=M.sort_map(values)),

  % slower
  %  M2 = [ C=sum([1 : CC in Chars, CC=C]) : C in Chars.remove_dups().sort()],
  % println(M2),

  nl.

letter_freq(S) = Map =>
  Map = new_map(),
  foreach(C in S)
    Map.put(C,Map.get(C,0)+1)
  end.


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).