/* 

  Two coins in Picat.

  This is a port of the R2 model TwoCoins.cs
  
  Output from the R2 model:
  '''
  (0) Mean: 0.339              firstCoin
  (0) Variance: 0.224303
  (1) Mean: 0.309              secondCoin
  (1) Variance: 0.213733
  Number of accepted samples = 847
  '''

  Cf my Gamble model gamble_two_coins.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.
% import ordset.

main => go.

/*

  var : first coin
  Probabilities:
  false: 0.6610147213459516
  true: 0.3389852786540484
  mean = 0.338985

  var : second coin
  Probabilities:
  false: 0.6728443743427971
  true: 0.3271556256572030
  mean = 0.327156

  var : both heads
  Probabilities:
  false: 1.0000000000000000
  mean = 0.0

*/
go ?=>
  reset_store,
  run_model(10_000,$model,[show_probs_trunc,mean % ,
                           % show_percentiles,
                           % show_hpd_intervals,hpd_intervals=[0.94],
                           % show_histogram,
                           % min_accepted_samples=1000,show_accepted_samples=true
                          ]),
  nl,
  % show_store_lengths,nl,
  % fail,
  nl.
go => true.
  
  
model() =>
  FirstCoin  = flip(1/2),
  SecondCoin = flip(1/2),
  BothHeads  = check( (FirstCoin, SecondCoin)),
  observe(not BothHeads),
  
  if observed_ok then
    add("first coin",FirstCoin),
    add("second coin",SecondCoin),
    add("both heads",BothHeads),    
  end.