Arithmetic/Rational: Difference between revisions

=={{header|Prolog}}==

Prolog supports rational numbers, where P/Q is written as P rdiv Q.

<lang Prolog>

divisor(N, Div) :-

Max is floor(sqrt(N)),

between(1, Max, D),

divmod(N, D, _, 0),

(Div = D; Div is N div D, Div =\= D).

divisors(N, Divs) :-

setof(M, divisor(N, M), Divs).

recip(A, B) :- B is 1 rdiv A.

sumrecip(N, A) :-

divisors(N, [1 | Ds]),

maplist(recip, Ds, As),

sum_list(As, A).

perfect(X) :- sumrecip(X, 1).

main :-

Limit is 1 << 19,

forall(

(between(1, Limit, N), perfect(N)),

(format("~w~n", [N]))),

halt.

?- main.

</lang>

{{Out}}

<pre>

6

28

496

8128

</pre>