Factors of an integer: Difference between revisions

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@@ Line 1,324: / Line 1,324: @@
 factor(N, Factors) :-
     Limit = float.truncate_to_int(math.sqrt(float(N))),
-	factor(N, 2, Limit, Unsorted),
+	factor(N, 2, Limit, [], Unsorted),
     list.sort_and_remove_dups([1, N | Unsorted], Factors).
-:- pred factor(int::in, int::in, int::in, list(int)::out) is det.
+:- pred factor(int::in, int::in, int::in, list(int)::in, list(int)::out) is det.
-factor(N, X, Limit, Accumulator) :-
+factor(N, X, Limit, !Accumulator) :-
     ( if X  > Limit
-          then Accumulator = []
+          then true
           else ( if 0 = N mod X
-                     then Accumulator = [X, N / X | Remaining]
+                     then !:Accumulator = [X, N / X | !.Accumulator]
-                     else Accumulator = Remaining ),
+                     else true ),
-               factor(N, X + 1, Limit, Remaining) ).
+               factor(N, X + 1, Limit, !Accumulator) ).
 :- func factor(int::in) = (list(int)::out) is det.
 factor(N) = Factors :- factor(N, Factors).
-:- end_module fac.</lang>
+:- end_module fac.
+</lang>
 ===Use and output===