/* 

  Sieve in Picat v3.

  From bench/sieve.pl  
  https://github.com/SWI-Prolog/bench

  For Picat v3
 

  This Picat model was created by Hakan Kjellerstrand, hakank@gmail.com
  See also my Picat page: http://www.hakank.org/picat/

*/


main => go.


go =>
  top.
  %% print the found primes
  % All=findall(X,bp.candidate(X)),
  % println(All),
  % nl.

go => true.

% """
% Benchmark prime number generation  using   the  sieve  of Eratosthenes
% algorithm with assert/retract. This benchmark tests assert/retract and
% JIT index generation and destruction.
%
% Auther: Jan Wielemaker
% Copyright: Public domain.
% """

top :- clean, primesx(10000), fail.
top.

clean :-
    bp.retractall($primesx(_)),
    bp.retractall($candidate(_)).
    

primesx(N) :-
    % hakank: We hard code 2 and 3 as the first two primes
    bp.assertz($candidate(2)), bp.assertz($candidate(3)),
    bp.forall($between(2, N, I), $assertz($candidate(I))),
    % foreach(I in 2..N) bp.assertz($candidate(I)), end,
    sieve(N).

sieve(Max) :-
    bp.retract($candidate(First)),
    !,
    bp.assertz($primesx(First)),
    First < Max,
    sieve(First, 2, Max),
    sieve(Max).
sieve(_).

sieve(N, Mul, Max) :-
    I is N*Mul,
    I =< Max,
    !,
    bp.retract($candidate(I)),
    Mul2 is Mul+1,
    sieve(N, Mul2, Max).
sieve(_, _, _).