:- use_module(library(random)).
?- random(X). % X = 0.3011486766485858.
?- random(0, 100, X). % X = 51.
% maybe: succeed/ fail with equal probabilty
?- maybe. % true.
?- maybe. % false.
% maybe/1 (P): succeed/ fail with P probabilty
?- maybe(0.333). % false.
?- maybe(0.333). % false.
?- maybe(0.333). % true.
% random permutation
?- random_perm2(A, B, X, Y). % A = X, B = Y.
?- random_perm2(A, B, X, Y). % A = Y, B = X.
% random element in list
?- random_member(X, [1, 2, 3, 4, 5]). % X = 2.
% random select element in list
?- random_select(X, [1, 2, 3, 4, 5], Y). % X = 3, Y = [1, 2, 4, 5].
% randset/3 (elements, range, list): ordered
?- randset(5, 100, X). % X = [30, 35, 51, 59, 73].
% randseq/3 (elements, range, list): unordered
?- randseq(5, 100, X). % X = [20, 12, 22, 100, 67].