/* 

  Medical diagnosis in Picat.

  https://edu.swi-prolog.org/mod/assign/view.php?id=249
  """
  Medical diagnosis

  Develop an expert system for medical diagnosis.

  Consider three diseases: flu, gastroenteritis and bronchitis.

  A priori, flu has probability 0.3, gastroenteritis 0 0.2, and bronchitis 0.25.

  If you have the flu, you may have the following symptons, associated with their
  probabilities (symptoms are not mutually exclusive):

    fever, 0.8
    cough 0.6
    sore throat 0.5
    headaches 0.4
    aches 0.7

  If you have gastroenteritis, you may have the following symptons, associated with their
  probabilities (symptoms are not mutually exclusive):

    diarrhea 0.8
    aches 0.7
    nausea 0.4
    fatigue 0.3

  If you have bronchitis, you may have the following symptons, associated with their probabilities
  (symptoms are not mutually exclusive):

    cough 0.8
    fatigue 0.7
    fever 0.3

  Compute the probability of each disease given that the patient has the symptoms fever and aches.

  Do the same supposing the patient adds that he also experiences fatigue.
  """


  This is a port of my Gamble model gamble_medical_diagnosis.rkt

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

*/

import ppl_distributions, ppl_utils.

main => go.

/*
  * With fever and aches:

    var : bronchitis
    Probabilities:
    false: 0.7790385805652982
    true: 0.2209614194347019
    mean = [false = 0.779039,true = 0.220961]

    var : flu
    Probabilities:
    true: 0.9830823189601815
    false: 0.0169176810398184
    mean = [true = 0.983082,false = 0.0169177]

    var : gastroenteritis
    Probabilities:
    false: 0.8025582834743140
    true: 0.1974417165256860
    mean = [false = 0.802558,true = 0.197442]

  * With fever, aches and fatigue
    var : bronchitis
    Probabilities:
    true: 0.7730173199635370
    false: 0.2269826800364631
    mean = [true = 0.773017,false = 0.226983]

    var : flu
    Probabilities:
    true: 0.9580674567000912
    false: 0.0419325432999088
    mean = [true = 0.958067,false = 0.0419325]

    var : gastroenteritis
    Probabilities:
    false: 0.6508659981768460
    true: 0.3491340018231541
    mean = [false = 0.650866,true = 0.349134]


*/
go ?=>
  reset_store,
  run_model(30_000,$model,[show_probs_trunc,mean]),
  nl,
  fail,
  nl.
go => true.

model() =>
   /*
     Consider three diseases: flu, gastroenteritis and bronchitis.   
     A priori, flu has probability 0.3, gastroenteritis 0.2, and bronchitis 0.25.
   
   */
   Flu             = flip(0.3),
   Gastroenteritis = flip(0.2),
   Bronchitis      = flip(0.25),

   
    
  /*
    If you have the flu, you may have the following symptons, associated with their
    probabilities (symptoms are not mutually exclusive):
      
    fever, 0.8
    cough 0.6
    sore throat 0.5
    headaches 0.4
    aches 0.7
  */
  Fever = cases([
                  [Flu,flip(0.8)],
                  [Bronchitis,flip(0.3)],
                  [true,false]
                ]),


  Cough = cases([
                  [Flu,flip(0.6)],
                  [Bronchitis,flip(0.8)],
                  [true,false]                 
                ]),

  SoreThroat = condt(Flu,flip(0.5),false),
  Headaches  = condt(Flu,flip(0.4),false),

  Aches      = condt(Flu,
                     flip(0.7),
                     condt(Gastroenteritis, flip(0.7), false)),

  /*
    If you have gastroenteritis, you may have the following symptons, associated with their
    probabilities (symptoms are not mutually exclusive):
      
    diarrhea 0.8
    aches 0.7
    nausea 0.4
    fatigue 0.3
  */

  Diarrhea = condt(Gastroenteritis, flip(0.8), false),
  Nausea   = condt(Gastroenteritis, flip(0.4), false),
  Fatigue  = condt(Gastroenteritis,
                   flip(0.3),
                   cond(Bronchitis, flip(0.7),false)),

  /*
      If you have bronchitis, you may have the following symptons, associated with their probabilities
      (symptoms are not mutually exclusive):
      
      cough 0.8
      fatigue 0.7
      fever 0.3
  */
  % These were commented in the Gamble model...
  /*
  if Bronchitis then
    if flip(0.8) == true then
      observe(Cough == true)
    end,
    if flip(0.7) == true then
      observe(Fatigue == true)
    end,    
    if flip(0.3) == true then
      observe(Fever == true)
    end    
  end,
  */
  
  observe(Fever==true),
  observe(Aches==true),
  % observe(Fatigue==true),  

  if observed_ok then
    add("flu",Flu),
    add("gastroenteritis",Gastroenteritis),
    add("bronchitis",Bronchitis),
  end.