Helper Swicollatz

Jan Burse, created Sep 15. 2018
/**
* Balanced execution of the collatz function.
* SWI-Prolog version.
*
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*/
:- use_module('../compat/swidistributed').
/*****************************************************************/
/* Normal Test Cases */
/*****************************************************************/
many :-
between(10000, 20000, X), collatz(X, _).
many2 :-
balance(between(10000, 20000, X), collatz(X, _), 2).
many4 :-
balance(between(10000, 20000, X), collatz(X, _), 4).
many8 :-
balance(between(10000, 20000, X), collatz(X, _), 8).
first :-
once((between(10000, 20000, X), collatz(X, _), X = 16666)).
first2 :-
once(balance(between(10000, 20000, X), (collatz(X, _), X = 16666), 2)).
first4 :-
once(balance(between(10000, 20000, X), (collatz(X, _), X = 16666), 4)).
first8 :-
once(balance(between(10000, 20000, X), (collatz(X, _), X = 16666), 8)).
/*****************************************************************/
/* The Collatz Function */
/*****************************************************************/
collatz(1, 0) :- !.
collatz(I, N) :- 1 =:= I/\1, !,
I0 is I*3+1, collatz(I0, N0), N is N0+1.
collatz(I, N) :-
I0 is I>>1, collatz(I0, N0), N is N0+1.

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