Converting minutes to hours in prolog

问题

I am trying to convert total minutes(N) to number of hours(H) and number of minutes(M) in prolog using this code (Have not implemented counting the minutes yet):

minutes_to_hours(N, H, M) :-

   (   N >= 60
   ->  H is H1+1,
       N is N1-60,
       minutes_to_hours(N, H, M)
   ;   writeln(H)
   ).

I get this error:

Arguments are not sufficiently instantiated
In:
[2] _1440 is _1446+1
[1] mins_to_hours_and_mins(60,_1508,_1510) at  line 1

回答1:

As you requested, a possible solution using recursion could be:

minutes_to_hours(Mins,Hours) :-
    (   Mins > 60 ->  
        M is Mins - 60,
        H1 is Hours + 1,
        minutes_to_hours(M,H1) ;
        format('Hours: ~w, Reminder: ~w~n',[Hours,Mins])
    ).

?- minutes_to_hours(125,0).
Hours: 2, Reminder: 5
true

However, you should prefer the solution of @CapelliC with mod and //.

回答2:

H1 is not instantiated, hence the error. But note there is no need for recursion, you can do it similarly to other languages:

?- [user].
|: minutes_to_hours(N, H, M) :-
|:   H is N // 60,
|:   M is N mod 60.
|: ^D% user://1 compiled 0.05 sec, 1 clauses
true.

?- minutes_to_hours(125,H,M).
H = 2,
M = 5.

来源：https://stackoverflow.com/questions/60262036/converting-minutes-to-hours-in-prolog