1/*
    2Meta-calls/nested probability computations.
    3Reasoning about the probabilities of queries within a probabilistic program.
    4Can be used to implement simple forms of combining rules.
    5In this example, max_true(G1,G2) succeeds with the success probability of 
    6the more likely argument.
    7From
    8De Raedt, Luc, and Angelika Kimmig. "Probabilistic (logic) programming concepts." Machine Learning (2015): 1-43.
    9*/
   10
   11
   12
   13:- use_module(library(pita)).   14
   15:- pita.   16
   17:- begin_lpad.   18
   19
   20
   21max(A,B,A):-
   22  A>=B.
   23
   24max(A,B,B):-
   25  B>=A.
   26
   27p(P):P.
   28
   29max_true(G1, G2) :-
   30  prob(G1, P1), 
   31  prob(G2, P2), 
   32  max(P1, P2, P), p(P).
   33
   34a:0.5. 
   35b0:0.7. 
   36b1:0.7. 
   37c:0.2.
   38
   39d :-
   40  a, \+ b0.
   41
   42e :- 
   43  b1, c.
   44:- end_lpad.