Descending primes: Difference between revisions

isPrime(2).

isPrime(N):-

between(3, inf, N),

N /\ 1 > 0, % odd

M is floor(sqrt(N)) - 1, % reverse 2*I+1

Max is M div 2,

forall(between(1, Max, I), N mod (2*I+1) > 0).

combi(0, _, []).

combi(N, [_|T], Comb):-

N > 0,

combi(N, T, Comb).

combi(N, [X|T], [X|Comb]):-

N > 0,

N1 is N - 1,

combi(N1, T, Comb).

descPrimes(Num):-

between(1, 9, N),

combi(N, [9, 8, 7, 6, 5, 4, 3, 2, 1], CList),

atomic_list_concat(CList, Tmp), % swi specific

atom_number(Tmp, Num), % int_list_to_number

isPrime(Num).

showList(List):-

findnsols(10, DPrim, (member(DPrim, List), writef('%9r', [DPrim])), _),

nl,

fail.

showList(_).

do:-findall(DPrim, descPrimes(DPrim), DList),

showList(DList).