trace
domains
    gamelist = symbol*
    teamlist = symbol*
    finallist = symbol*
    newlist = symbol*
    
database
    players(integer,symbol,gamelist)
    games(symbol,integer)
    student_db(integer,symbol)
    
    
predicates
    find_players(symbol,teamlist)
    enter_game()
    go
    repeate
    initialize()
    member(symbol,gamelist)
    display_list(finallist,integer)
    display_db(finallist,integer)
    combination(integer,finallist,newlist)
    
goal 
    go.
    
    
clauses        
    repeate.
    repeate :- repeate.
    
    go :-
        initialize(),
        enter_game().
    
    initialize() :-
        assert(players(1,"hemal",[cricket,football])),
        assert(players(2,"shashank",[football,carrom])),
        assert(players(3,"nilay",[carrom,chess])),
        assert(players(4,"khilan",[cricket,chess])),
        assert(players(5,"gediya",[football,carrom])),
        assert(players(6,"kk",[carrom,cricket])),
        assert(players(7,"hh",[carrom,football])).
        
    member(X,[X|_]).
    member(X,[_|Tail]) :- member(X,Tail).
        


    enter_game() :-
        write("Enter the Name of Game : "),
        readln(GNAME),
        find_players(GNAME,TEAMLIST),
        display_db(FINALLIST,0).
    
    find_players(GNAME,TEAMLIST) :-
        players(NO,NAME,G_LIST),
        member(GNAME,G_LIST),
        assert(student_db(NO,NAME)),
        fail.

    find_players(GNAME,TEAMLIST).
        
    
    display_db(FINALLIST,CNT) :-
        
        student_db(N1,N),
        FINALLIST1 = [N | FINALLIST],
        write(N), write(" "),
        retract(student_db(N1,N)),
        CNT1 = CNT + 1,
        display_db(FINALLIST1,CNT1).
        
    display_db(FINALLIST,CNT) :- 
%        display_list(FINALLIST,CNT),
        nl,
        write("The possible combinations are : "),
        combination(2,FINALLIST,NEWLIST),
        nl,
        readchar(_),
        write(NEWLIST),
        fail.
    
    
    display_list([H | T],CNT) :-
    
        TMPLIST1 = [H|T],
        write(H),        
        CNT1 = CNT - 1,
        CNT > 0,
        display_list(T,CNT1).
        
        
    combination(NPLAYER,[X|TAIL],[X|COMB]) :-
        NPLAYER > 0,
        TMP = NPLAYER - 1,
        combination(TMP,TAIL,COMB).
        
    combination(NPLAYER,[_|TAIL],COMB) :-
        NPLAYER > 0,
        combination(NPLAYER,TAIL,COMB).
        
    combination(0,_,[]).