%Source: https://sites.google.com/site/prologsite/prolog-problems %query: prime_list(g,g,f). % 2.04 (*) A list of prime numbers. % Given a range of integers by its lower and upper limit, construct a % list of all prime numbers in that range. % prime_list(A,B,L) :- L is the list of prime number P with A <= P <= B prime_list(A,B,L) :- A =< 2, !, p_list(2,B,L). prime_list(A,B,L) :- A1 is (A // 2) * 2 + 1, p_list(A1,B,L). p_list(A,B,[]) :- A > B, !. p_list(A,B,[A|L]) :- is_prime(A), !, next(A,A1), p_list(A1,B,L). p_list(A,B,L) :- next(A,A1), p_list(A1,B,L). next(2,3) :- !. next(A,A1) :- A1 is A + 2. is_prime(2). is_prime(3). is_prime(P) :- integer(P), P > 3, P mod 2 =\= 0, \+ has_factor(P,3). % has_factor(N,L) :- N has an odd factor F >= L. % (integer, integer) (+,+) has_factor(N,L) :- N mod L =:= 0. has_factor(N,L) :- L * L < N, L2 is L + 2, has_factor(N,L2).
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