```    1/*
2The Indian GPA Problem. From
3http://www.robots.ox.ac.uk/~fwood/anglican/examples/viewer/?worksheet=indian-gpa
4"This example was inspired by Stuart Russell...the problem is: if you observe
5that a student GPA is exactly 4.04.0 in a model of transcripts of students
6from the USA (GPA's from 0.00.0 to 4.04.0 and India (GPA's from 0.00.0 to
710.010.0) what is the probability that the student is from India?...
8As we know from statistics, given the mixture distribution and given the
9fact that his/her GPA is exactly 4.04.0, the probability that the student
10is American must be 1.01.0
11(i.e. zero probability that the student is from India)."
12Probabilistic logic program from
13https://github.com/davidenitti/DC/blob/master/examples/indian-gpa.pl
14*/
15:- use_module(library(mcintyre)).   16
17:- if(current_predicate(use_rendering/1)).   18:- use_rendering(c3).   19:- endif.   20:- mc.   21:- begin_lpad.   22
23is_density_A:0.95;is_discrete_A:0.05.
24% the probability distribution of GPA scores for American students is
25% continuous with probability 0.95 and discrete with probability 0.05
26
27agpa(A): beta(A,8,2) :- is_density_A.
28% the GPA of American students follows a beta distribution if the
29% distribution is continuous
30
31american_gpa(G) : finite(G,[4.0:0.85,0.0:0.15]) :- is_discrete_A.
32% the GPA of American students is 4.0 with probability 0.85 and 0.0 with
33% probability 0.15 if the
34% distribution is discrete
35american_gpa(A):- agpa(A0), A is A0*4.0.
36% the GPA of American students is obtained by rescaling the value of agpa
37% to the (0.0,4.0) interval
38is_density_I : 0.99; is_discrete_I:0.01.
39% the probability distribution of GPA scores for Indian students is
40% continuous with probability 0.99 and discrete with probability 0.01
41igpa(I): beta(I,5,5) :- is_density_I.
42% the GPA of Indian students follows a beta distribution if the
43% distribution is continuous
44indian_gpa(I): finite(I,[0.0:0.1,10.0:0.9]):-  is_discrete_I.
45% the GPA of Indian students is 10.0 with probability 0.9 and 0.0 with
46% probability 0.1 if the
47% distribution is discrete
48indian_gpa(I) :- igpa(I0), I is I0*10.0.
49% the GPA of Indian students is obtained by rescaling the value of igpa
50% to the (0.0,4.0) interval
51nation(N) : finite(N,[a:0.25,i:0.75]).
52% the nation is America with probability 0.25 and India with probability 0.75
53student_gpa(G):- nation(a),american_gpa(G).
54% the GPA of the student is given by american_gpa if the nation is America
55student_gpa(G) :- nation(i),indian_gpa(G).
56% the GPA of the student is given by indian_gpa if the nation is India
57
58:- end_lpad.```

?- `mc_lw_sample(nation(a),student_gpa(4.0),1000,PPost)`. % probability that the nation is America given that the student got 4.0 % in his GPA % expected result: 1.0 ?- `mc_sample(nation(a),1000,PPrior)`. % prior probability that the nation is America % expected result: 0.25

*/