/* 

  Jobs problem in Picat.

  From 
  http://www.anselm.edu/internet/compsci/faculty_staff/mmalita/HOMEPAGE/logic/jobs1.txt
  """
  File: Jobs1.pl
  Author: (sol MM)	
  Title: Finding the profession
   
  Smith, Baker, Carpenter and Tailor have each a profession
  (smith, baker, carpenter, tailor) but not showed by their names.

  Each of them has a son.
  But the sons also do not have the profession showed by their name.

  If you know that:
  1) no son has the same profession as his father has
  and
  2) Baker has the same profession as Carpenter's son has
  and
  3) Smith's son is a baker.

  find the professions of the parents and sons.
  """

  Solution:
  [carpenter,smith,baker,tailor]
  [baker,carpenter,smith,tailor]



  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 =>
  sol([S,B,C,T],[Son_S, Son_B, Son_C, Son_T]),
  println('Father''s professions'=[S,B,C,T]),
  println('Son''s professions   '=[Son_S, Son_B, Son_C, Son_T]),
  nl.

/* list of professions */
professions(Professions) => Professions = [smith,baker,carpenter,tailor].

/* S = Smith's profession 
   B = Baker's profession 
   C = Carpenter's profession
   T = Taylor's profession

   Son_S = Smith son's profession 
   Son_B = Baker son's profession 
   Son_C = Carpenter son's profession
   Son_T = Taylor son's profession
*/
sol([S,B,C,T],[Son_S, Son_B, Son_C, Son_T]) => 
   professions(L),
   member(S,L),not(S=smith),
   member(B,L),not(B=baker),
   member(C,L),not(C=carpenter),
   member(T,L),not(T=taylor),

   /* The sons do not have the same profession as their name shows */
   member(Son_S,L),not(Son_S=smith),
   member(Son_B,L),not(Son_B=baker),
   member(Son_C,L),not(Son_C=carpenter),
   member(Son_T,L),not(Son_T=taylor),

   /* The sons do not have the same profession as their fathers either */
   not(S = Son_S),  % hakank: The source stated "not S = Son_F" which is wrong
   not(B = Son_B),
   not(C = Son_T),
   not(T = Son_C),



   /* Baker has the same profession as Carpenter's son. */
   B=Son_C, 

   /* Smith's son is a baker */
   Son_S=baker,

   distinct([S, B, C, T]), % hakank: added this
   distinct([Son_S, Son_B, Son_C, Son_T]). % hakank: added this



set([]) => true.
set([H|T]) => not(member(H,T)),set(T).

distinct(M) => set(M).