% flights.pl:
:-op(50,xfy,:).
timeTable(edinburgh,london,[INDENT][9:40/10:50/ba4733/daily,[/INDENT]
[INDENT]13:40/14:50/ba4753/daily,
19:40/20:50/ba4833/[mon,tue,wed,thu,fri,sun]]).
[/INDENT]
timeTable(london,edinburgh,[INDENT][9:40/10:50/ba4732/daily,
11:40/12:50/ba4752/daily,
18:40/19:50/ba4822/[mon,tue,wed,thu,fri]]).
[/INDENT]
timeTable(london,ljubljana,[INDENT][13:20/16:20/sa201/[fri],
13:20/16:20/sa213/[sun]]).
[/INDENT]
timeTable(ljubljana,london,[INDENT][11:10/12:20/sa200/[fri],
11:25/12:20/sa212/[sun]]).
[/INDENT]
timeTable(london,zurich,[INDENT][9:10/11:45/ba510/daily,
14:45/17:20/sr459/daily]).
[/INDENT]
timeTable(zurich,london,[INDENT][9:00/9:40/ba613/[mon,tue,wed,thu,fri,sat],
16:10/16:55/sr806/[mon,tue,wed,thu,fri,sun]]).
[/INDENT]
timeTable(london,milano,[INDENT][8:30/11:20/ba510/daily,
11:00/13:50/az459/daily]).
[/INDENT]
timeTable(milano,london,[INDENT][9:10/10:00/az458/daily,
12:20/13:10/ba511/daily]).
[/INDENT]
timeTable(ljubljana,zurich,[INDENT][11:30/12:40/sa322/[tue,thu]]).
[/INDENT]
timeTable(zurich,ljubljana,[INDENT][13:30/14:40/sa323/[tue,thu]]).
[/INDENT]
timeTable(zurich,milano,[INDENT][7:55/8:45/sr620/daily]).
[/INDENT]
timeTable(milano,zurich,[INDENT][9:25/10:15/sr621/daily,[/INDENT]
[INDENT]12:45/13:35/sr623/daily]).
[/INDENT]
 
flight(City1,City2,Day,Flight,Departure,Arrival):-[INDENT]timeTable(City1,City2,TimeTable),[/INDENT]
[INDENT]member(Departure/Arrival/Flight/DayTimeTable,TimeTable),[/INDENT]
[INDENT]dayOfFlight(Day,DayTimeTable).
[/INDENT]
 
dayOfFlight(Day,daily):-[INDENT]member(Day,[mon,tue,wed,thu,fri,sat,sun]).[/INDENT]
dayOfFlight(Day,List):-[INDENT]member(Day,List).
[/INDENT]
 
travel(City1,City2,Day,Letovi):-[INDENT]travel0(City1,City2,Day,0:0,Letovi).
[/INDENT]
 
% Arrival1 contains the time of arrival in City1;
% it limits the no. of flights with which one can continue travelling
travel0(City1,City2,Day,Arrival1,[City1-City2:Flight:Departure1]):-[INDENT]flight(City1,City2,Day,Flight,Departure1,_),[/INDENT]
[INDENT]possibleTransfer(Arrival1,Departure1).
[/INDENT]
 
travel0(City1,City2,Day,Arrival1,[City1-City3:Flight1:Departure1|Residual]):-[INDENT]flight(City1,City3,Day,Flight1,Departure1,Arrival3),[/INDENT]
[INDENT]possibleTransfer(Arrival1,Departure1),[/INDENT]
[INDENT]travel0(City3,City2,Day,Arrival3,Residual).
[/INDENT]
 
timeOfDeparture([_-_:_:Departure|_],Departure).
 
possibleTransfer(Hour1:Minute1,Hour2:Minute2):-[INDENT]60*(Hour2-Hour1)+Minute2-Minute1>=40.
[/INDENT]
 
member(X,[X|_]).member(X,[_|Rest]):-[INDENT]member(X,Rest).
[/INDENT]

% 8queens.pl: 
% Program for solving the 8 queens problem 
% List is an output argument in which the solution of the problem is written. 
% Order of queens is represented with a list of coordinates of rows and columns. 
solution(Order):- 
Order=[_/0,_/1,_/2,_/3,_/4,_/5,_/6,_/7], 
Rows=[0,1,2,3,4,5,6,7], 
Diag_Asc=[-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6,7], 
Diag_Des=[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14], 
solve(Order, Rows, Diag_Asc, Diag_Des). 
% Arguments of predicate solve are in order: 
% -solution of a problem (permitted order of queens); 
% before execution of the procedure coordinates of columns need to be instantiated. 
% -row of a queen that is currently being processed; 
% -list of free descending diagonals which are described by the difference 
% between row and column for every belonging field; 
% -list of free ascending diagonals which are described by the sum 
% between row and column for every belonging field; 
solve([],_,_,_). 
solve([Row/Column|Tail], R, Da, Dd):- 
remove(Row,R,R1), % removes Row in R, rezult is R1 
U is -Row+Column, 
remove(U, Da, Da1), 
S is Row+Column, 
remove(S, Dd, Dd1), 
solve(Tail, R1, Da1, Dd1). 
remove(Element, [Element|Tail], Tail). 
remove(Element, [Element1|Tail], [Element1|Tail1]):- 
remove(Element,Tail,Tail1).