e5f4633c39
which included commits to RCS files with non-trunk default branches. git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@5 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
67 lines
1.5 KiB
Prolog
67 lines
1.5 KiB
Prolog
% Sieve of eratosthenes to compute primes
|
|
% thom fruehwirth 920218-20, 980311
|
|
% christian holzbaur 980207 for Sicstus CHR
|
|
|
|
:- use_module(library(chr)).
|
|
|
|
handler primes.
|
|
|
|
|
|
% like chemical abstract machine
|
|
|
|
constraints primes/1, prime/1.
|
|
|
|
primes(1) <=> true.
|
|
primes(N) <=> N>1 | M is N-1, prime(N), primes(M).
|
|
|
|
absorb(J) @ prime(I) \ prime(J) <=> J mod I =:= 0 | true.
|
|
|
|
|
|
% shorter variant
|
|
|
|
constraints primes2/1.
|
|
|
|
primes2(N) ==> N>2 | M is N-1, primes2(M).
|
|
|
|
absorb2(J) @ primes2(I) \ primes2(J) <=> J mod I =:= 0 | true.
|
|
|
|
|
|
% faster variant
|
|
|
|
primes1(N):- primes1(2,N).
|
|
|
|
constraints primes1/2, prime1/1.
|
|
|
|
primes1(N,M) <=> N> M | true.
|
|
primes1(N,M) <=> N=<M | N1 is N+1, prime1(N), primes1(N1,M).
|
|
|
|
absorb1(J) @ prime1(I) \ prime1(J) <=> J mod I =:= 0 | true.
|
|
|
|
|
|
% faster variant, rule order sensitive
|
|
|
|
constraints primes3/1, prime3/1.
|
|
|
|
primes3(N) ==> prime3(2).
|
|
primes3(N),prime3(M) <=> M is N+1 | true.
|
|
|
|
prime3(N) ==> M is N+1, prime3(M).
|
|
absorb3(J) @ prime3(I) \ prime3(J) <=> J mod I =:= 0 | true.
|
|
|
|
|
|
% Concurrent program according to Shapiro
|
|
|
|
constraints primes/2,integers/3,sift/2,filter/3.
|
|
|
|
primes(N,Ps) <=> integers(2,N,Ns), sift(Ns,Ps).
|
|
|
|
integers(F,T,Ns) <=> F > T | Ns=[].
|
|
integers(F,T,Ns) <=> F =< T | Ns=[F|Ns1], F1 is F+1, integers(F1,T,Ns1).
|
|
|
|
sift([P|Ns],Ps) <=> Ps=[P|Ps1], filter(Ns,P,Ns1), sift(Ns1,Ps1).
|
|
sift([],Ps) <=> Ps=[].
|
|
|
|
filter([X|In],P,Out) <=> 0 =\= X mod P | Out=[X|Out1], filter(In,P,Out1).
|
|
filter([X|In],P,Out) <=> 0 =:= X mod P | filter(In,P,Out).
|
|
filter([],P,Out) <=> Out=[].
|