/* 

  Student mood after exam in Picat.

  Cf my Gamble model gamble_student_mood_after_exam.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.
import util.

main => go.

/*

  var : difficulty
  Probabilities:
  easy: 0.5982384823848238
  hard: 0.4017615176151761
  mean = [easy = 0.598238,hard = 0.401762]

  var : grade
  Probabilities:
  good: 0.6744579945799458
  bad: 0.3255420054200542
  mean = [good = 0.674458,bad = 0.325542]

  var : mood
  Probabilities:
  good: 0.5000000000000000
  bad: 0.5000000000000000
  mean = [good = 0.5,bad = 0.5]

  var : preparation
  Probabilities:
  good: 1.0000000000000000
  mean = [good = 1.0]

*/
go ?=>
  reset_store,
  run_model(10_000,$model,[show_probs_trunc,mean]),
  nl,
  % fail,
  nl.
go => true.
  
  
model() =>
  BadGood = [bad,good],
  Difficulty = categorical([0.6,0.4],[easy,hard]),
  Preparation = categorical([0.7,0.3],BadGood),

  Grade = cases([ [(Difficulty == easy, Preparation==bad), categorical([0.95,0.05],BadGood)],
                  [(Difficulty == easy, Preparation==good), categorical([0.5,0.5],BadGood)],
                  [(Difficulty == hard, Preparation==bad), categorical([0.6,0.4],BadGood)],
                  [(Difficulty == hard, Preparation==good), categorical([0.05,0.95],BadGood)],
                  [true, unknown_grade]  
                ]),

  Mood = cond(Grade == bad,
              categorical([0.9,0.1],BadGood),
              categorical([0.3,0.7],BadGood)),

  % observe(Difficulty==easy),
  observe(Preparation==good),
  % observe(Grade==bad),
  % observe(Mood==bad),
  if observed_ok then
    add_all([ ["difficulty",Difficulty],
              ["preparation",Preparation],
              ["grade",Grade],
              ["mood",Mood]
             ])
  end.