%Source: https://sites.google.com/site/prologsite/prolog-problems %query:prime_factors(g,f). % 2.02 (**) Determine the prime factors of a given positive integer. % prime_factors(N, L) :- L is the list of prime factors of N. % (integer,list) (+,?) prime_factors(N,L) :- N > 0, prime_factors(N,L,2). % prime_factors(N,L,K) :- L is the list of prime factors of N. It is % known that N does not have any prime factors less than K. prime_factors(1,[],_) :- !. prime_factors(N,[F|L],F) :- % N is multiple of F R is N // F, N =:= R * F, !, prime_factors(R,L,F). prime_factors(N,L,F) :- next_factor(N,F,NF), prime_factors(N,L,NF). % N is not multiple of F % next_factor(N,F,NF) :- when calculating the prime factors of N % and if F does not divide N then NF is the next larger candidate to % be a factor of N. next_factor(_,2,3) :- !. next_factor(N,F,NF) :- F * F < N, !, NF is F + 2. next_factor(N,_,N). % F > sqrt(N)
content may be truncated. 'popout' for larger text window.
