/*
Collatz Conjecture: no matter what value of N, the specified sequence will always reach 1.
For any positive integer N, to get next integer, do:
- if N is even, divide by 2
- if N is odd, multiply by 3 and add 1, i.e 3xN + 1
Repeat indefinitely to obtain the hailstone sequence N_0, N_1, N_2, ...
https://en.wikipedia.org/wiki/Collatz_conjecture
*/
:- use_module(library(clpfd)).
hailstone(N, N).
hailstone(N_0, N) :-
N_0 #= 2 * N_1,
hailstone(N_1, N).
hailstone(N_0, N) :-
N_0 #= 2 * _ + 1,
N_1 #= 3 * N_0 + 1,
hailstone(N_1, N).
%:- hailstone(3, N), print(N), nl, N = 1.
:- initialization main.
main :-
hailstone(3, N), print(N), nl, N = 1,
halt.
% N = 3
% N = 10
% N = 5
% N = 16
% N = 8
% N = 4
% N = 2
% N = 1