/*================================================================ | | Travel Agent Tools. | | This file defines rules based on the flight database provided as database.pl. | | The database has three types of atomic predicates: | 1) segment(flight(Airline,Number), OriginAirport, DestinationAirport, DepartureTime, ArrivalTime) | 2) airport(Abbreviation, State, GMT) | 3) airline(Code,Name) | | flight(Airline,Number) is a functor that represents a particular flight, | but note that airlines often define a flight to have multiple segments. | So it is not enough to say that you are using flight(ua,10), but | you would need to differentiate between whether you are using the leg | from LGA -> IAH, from IAH-> DEN, or DEN -> BOI. | | time(H,M) is always expressed in 24-hour time, such that 0 <= H <= 23, | 0 <= M <= 59. | | All flight times are expressed in local time for the relevant airport | (and without any use of daylight savings times). | | The airport abbreviation is the standard 3-letter code (e.g. stl). | The airport's GMT time is an integer that represents the difference | in the number of hours between the airport's local time and | Greenwich Mean Time. For example, St. Louis is at -6 GMT, which means that when | it is 11:00am in Greenwich, it is 5:00am in St. Louis. | | The Airline Names are only necessary for pretty printing | +================================================================*/ /*---------------------------------------------------------------- | Predicate: minutes(time(H,M), N). | | N is the number of minutes from the start of the day until time(H,M). | | Preconditions: H and M must be bound | | Examples: | | ?- minutes(time(13,45), N). | N = 825. | | ?- minutes(time(0,0), N). | N = 0. +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: as_early(T1,T2). | | true if time T1 is at least as early in the day as T2. | (We assume that both are expressed in the same timezone). | | Preconditions: both T1 and T2 must be bound. | | Examples: | ?- as_early(time(5,30), time(8,45)). | true. | | ?- as_early(time(5,30), time(5,30)). | true. | | ?- as_early(time(23,58), time(0,05)). | false. +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: between(T1,T2,T3). | | true if time T2 is within the cyclical range [T1,T3]. | (We assume that all times are expressed in the same timezone). | | Preconditions: all of T1, T2, and T3 must be bound. | | Examples: | ?- between(time(5,30), time(7,13), time(8,45)). | true. | | ?- between(time(5,30), time(8,45), time(8,45)). | true. | | ?- between(time(5,30), time(5,30), time(8,45)). | true. | | ?- between(time(5,30), time(4,30), time(8,45)). | false. | | ?- between(time(5,30), time(11,30), time(8,45)). | false. | | ?- between(time(5,30), time(5,30), time(5,30)). | true. | | ?- between(time(5,30), time(5,29), time(5,30)). | false. | | ?- between(time(22,15), time(23,49), time(1,23)). | true. | | ?- between(time(22,15), time(1,15), time(1,23)). | true. | | ?- between(time(22,15), time(5,05), time(1,23)). | false. +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: elapsed(T1,T2,M). | | Elapsed time from T1 to T2 is M, where T1 and T2 are | time(H,M) expressions and M expresses the number of minutes elapsed | | Preconditions: both T1 and T2 must be bound. | | T1 and T2 are assumed to be expressed in the same time zone, and that | T2 is the next occurrence of that time of day following T1. That is, | the elapsed time should be in the range [0,1439], as it is strictly less than 24 hours. | | Examples: | ?- elapsed(time(5,30), time(8,45), M). | M = 195. | | ?- elapsed(time(23,58), time(0,05), M). | M = 7 +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: gmt(Airport, Local, Global) | | True if Global is the GMT time that is equal to the Local time expressed at Airport. | This should be applicable with either one of Local or Global being unbound. That is | | Preconditions: Airport and at least one of Local or Global must be bound. | | Examples: | ?- gmt(stl, time(11,30), G). | G = time(17,30). | | ?- gmt(stl, L, time(17,30)). | L = time(11,30). +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: flight_time(F, Origin, Destination, T) | | True if the segment of flight F from Origin to Destination has | an elapsed time of T minutes (taking into consideration the time zones | of the airports). | | Preconditions: F, Origin, and Destination must be bound | | Examples: | ?- flight_time(flight(aa,1040), stl, ord, T). | T = 75. | | ?- flight_time(flight(dl,2088), stl, slc, T). | T = 197. +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: flies(Airline, Airport). | | True if Airline has at least one flight into or out of Airport | | Examples: | ?- flies(as,stl). /* Alaskan Airlines */ | true. | | ?- flies(ha,stl). /* Hawaiian Airlines */ | false. | | ?- setof(A, flies(A,pvd), L). | L = [b6, dl, e9, ev, ua, us, wn, yv]. +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: nonstop(Origin, Destination). | | True if there exists a direct flight segment from Origin to Destination. | | Examples: | ?- nonstop(stl,den). /* Denver */ | true. | | ?- nonstop(stl,cos). /* Colorado Springs */ | false. +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: nonstop(Origin, Destination, Airline). | | True if Airline operates a direct flight segment from Origin to Destination. | | Examples: | ?- nonstop(stl,den,wn). /* Southwest Airlines */ | true. | | ?- nonstop(stl,den,aa). /* American Airlines */ | false. | | ?- setof(D, nonstop(stl,D,dl), L). /* Destinations from St. Louis on Delta */ | L = [atl, dtw, msp, slc]. +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: arrivals(Airport, Start, End, L). | | L is a list of all flights that arrive at Airport during the interval | starting at time Start and ending with time End (where it is possible | that the interval wraps around midnight). | | Preconditions: Airport, Start, and End must be bound | | Examples: | | ?- arrivals(stl, time(10,00), time(10,10), L). | L = [flight(e9, 3360), flight(e9, 4102), flight(wn, 4)]. | | ?- arrivals(stl, time(9,25), time(9,25), L). | L = [flight(wn, 2425), flight(wn, 340), flight(wn, 3482), flight(wn, 3861), flight(wn, 683), flight(wn, 749)]. | | ?- arrivals(lax, time(23,50), time(0,45), L). | L = [flight(aa, 1035), flight(aa, 2497), flight(b6, 677), flight(dl, 2363), flight(ua, 1445)] +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: wait(F1, Airport, F2, W) | | W is the wait time (in minutes) between the arrival of F1 at Airport | and the subsequent departure of F2. | | Preconditions: F1, Airport, and F2 must be bound. | | Examples: | | ?- wait(flight(wn,369), mdw, flight(wn,369), W). | W = 50 ; | | ?- wait(flight(wn,2766), mdw, flight(wn,2766), W). | W = 40 ; +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: connecting(F1, Airport, F2, MinGap, MaxGap) | | true if it is possible to arrive at Airport on F1 and depart on F2. | | To make a connection the gap between the arrival of F1 and subsequent | departure of F2 must be at least MinGap minutes, and at most MaxGap minutes. | | Preconditions: Airport, MinGap, MaxGap must be bound. | | Examples: | | ?- connecting(flight(wn,1359), stl, F, 20, 40). | F = flight(fl, 544) ; | F = flight(wn, 1281) ; | F = flight(wn, 1359) ; | F = flight(wn, 2319) ; | | ?- connecting(F, stl, flight(wn,1359), 20, 40). | F = flight(e9, 3360) ; | F = flight(e9, 4102) ; | F = flight(aa, 1266) ; | F = flight(wn, 1359) ; | F = flight(wn, 2319) ; | F = flight(wn, 4) ; | +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: connecting_airline(F1, Airport, F2, MinGap, MaxGap) | | Similar to connecting predicate, except that F1 and F2 must use same airline. | | Examples: | | ?- connecting_airine(flight(wn,1359), stl, F, 20, 40). | F = flight(wn, 1281) ; | F = flight(wn, 1359) ; | F = flight(wn, 2319) ; | | ?- connecting_airline(F, stl, flight(wn,1359), 20, 40). | F = flight(wn, 1359) ; | F = flight(wn, 2319) ; | F = flight(wn, 4) ; | +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: travel_time(Itinerary, T) | | True if the end-to-end travel time for the given itinerary is T. | | Examples: | | ?- travel_time([pwm, flight(b6, 609), jfk], T). | T = 83 . | | ?- travel_time([pwm, flight(b6, 609), jfk, flight(dl, 1394), pdx], T). | T = 520 . | | ?- travel_time([pwm, flight(ev, 4091), ewr, flight(wn, 369), mdw, flight(wn, 2766), pdx], T). | T = 594 . | | /* Travel from Pago Pago, American Somoa to St. Croix, U.S. Virgin Islands */ | ?- travel_time([ppg, flight(ha,466), hnl, flight(ua,106), lax, flight(dl,1406), dtw, flight(e9,3489), | phl, flight(aa,1007), mia, flight(aa,1165), stx], T). | T = 2280 . /* Note that this is more than 24 hours. */ | +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: pretty_print(Itinerary) | | Produces pretty output to describe itinerary, which is represented | as an odd-length alternating list of airport/flight/airport | progression, such as: | | [ppg, flight(ha,466), hnl, flight(ua,106), lax, flight(dl,1406), dtw, | flight(e9,3489), phl, flight(aa,1007), mia, flight(aa,1165), stx] | | The output for this example appears as: | | Depart from PPG at 23:20 on Hawaiian Airlines flight #466 arriving at HNL at 5:40 | Depart from HNL at 13:34 on United Airlines flight #106 arriving at LAX at 21:00 | Depart from LAX at 23:00 on Delta Airlines flight #1406 arriving at DTW at 6:26 | Depart from DTW at 8:10 on Pinnacle Airlines flight #3489 arriving at PHL at 10:04 | Depart from PHL at 12:35 on American Airlines flight #1007 arriving at MIA at 15:25 | Depart from MIA at 16:45 on American Airlines flight #1165 arriving at STX at 20:20 | Total travel time is 2280 minutes. | | Note: string atoms can be uppercased using the built-in predicate upcase_atom(Original,Upper). | +----------------------------------------------------------------*/ % ... your code here ... /*---------------------------------------------------------------- | Predicate: plan(Origin, Destination, MinConnect, MaxHops, MaxTime, Itinerary) | | Generate an itinerary going from Origin to Destination | (which never passes through any airport more than once) | subject to the following additional constraints. | | MinConnect represents the tightest connection allowed, expressed in minutes | (e.g., 30 means that there must be at least 30 minutes between one arrival and connecting departure) | | MaxHops represents the maximum number of segments that may be used | (e.g., 1 means that it must be a nonstop) | | MaxTime represents the maximum end-to-end travel time for a passenger that is allowed. | That is, in actual clock time, the length from the very first departure to the final arrival. | | Example: | | ?- plan(pwm, pdx, 30, 3, 600, I). /* From Portland, Maine to Portland, Oregon in 10 hours */ | I = [pwm, flight(b6, 609), jfk, flight(dl, 1394), pdx] ; | I = [pwm, flight(ev, 6046), iad, flight(ua, 1671), pdx] ; | I = [pwm, flight(ev, 6046), iad, flight(ua, 72), den, flight(ua, 745), pdx] ; | I = [pwm, flight(ev, 4091), ewr, flight(wn, 369), mdw, flight(wn, 2766), pdx] ; | | (although order of results may vary) +----------------------------------------------------------------*/ % ... your code here ... /*====================================== Extra Credit ======================================*/ /*--------------------------------------------------------------------------------------- | Be the first to convince me that one of my published examples produces the wrong result. | (+1 extra credit per example). +----------------------------------------------------------------------------------------*/ /*---------------------------------------------------------------- | Predicate: plan(Origin, Destination, EarliestDeparture, LatestDeparture, | MinConnect, MaxHops, MaxTime, Itinerary) | | EarliestDeparture is a time specification that is the earliest time | of day the traveler is able to depart the origin. | | LatestDepaurture is a time specification that is the latest time of day the traveler | is able to depart the origin. | | MinConnect represents the tightest connection allowed, expressed in minutes | (e.g., 30 means that there must be at least 30 minutes between one arrival and connecting departure) | | MaxHops represents the maximum number of segments that may be used | (e.g., 1 means that it must be a nonstop) | | MaxTime represents the maximum end-to-end travel time for a passenger that is allowed. | That is, in actual clock time, the length from the very first departure to the final arrival. +----------------------------------------------------------------*/