Prolog date_time_stamp [closed]

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Closed 5 years ago.

Trying to make a rule within prolog, which would ask if any messages where sent between 2 individuals (where both individuals can be the recipient or the sender of the message) before a given date. After calling whether it is true or not, it is to print all the logs where the 2 users have exchanged messages before the given time.

so far i thought,

msgbefore(X,Y,D) :-
    message(X,Y,D1),
    date_time_stamp(D),
    date_time_stamp(D1),
    D1 < D, 
message(Y,X,D1),
    date_time_stamp(D),
    date_time_stamp(D1),
    D1 < D.

database consists of:

message(sonny,robert,'2012-05-12').
message(robert,sarah,'2012-05-12').
message(julie,mary,'2012-05-12').
message(fred,nayna,'2012-05-13').
message(fred,daniel,'2012-05-14').
message(nayna,lucia,'2012-05-15').

please help,

回答1:

Just an hint: date_time_stamp requires 2 arguments and is rather difficult to use, but since your dates are provided as atoms in standard form, you can directly compare them. For instance

1 ?- message(A,B,Date),Date @< '2012-05-13'.
A = sonny,
B = robert,
Date = '2012-05-12' ;
...

来源：https://stackoverflow.com/questions/20895795/prolog-date-time-stamp