/*

  Rot 13 in Picat.

  See 
     http://en.wikipedia.org/wiki/ROT13
     http://rosettacode.org/wiki/Rot-13

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

*/

% import util.

main => go.

go =>
  S = "Big fjords vex quick waltz nymph!",
  println(S),
  println(rot13(S)),
  println(rot13(rot13(S))),

  nl.
    
% Rot 13 using a map
rot13(S) = S2 =>
  lower(Lower),
  upper(Upper),
  M = create_map(Lower, Upper),
  % If a char is not in a..zA..z then show it as it is.
  S2 := [M.get(C,C) : C in S].

create_map(Lower, Upper) = M =>
  M = new_map(),
  Len = Lower.length,
  LDiv := Lower.length div 2,
  foreach(I in 1..Len)
    II = (LDiv+I) mod Len,
    if II == 0 then II := Len end,
    M.put(Upper[I],Upper[II]),
    M.put(Lower[I],Lower[II])
  end.

lower("abcdefghijklmnopqrstuvwxyz").
upper("ABCDEFGHIJKLMNOPQRSTUVWXYZ").