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:- object(faa).
:- info([
version is 1.0,
date is 2004/5/10,
author is 'Paulo Moura',
comment is 'Adaptation of the command language DCG example from the Amzi! Prolog manual.']).
:- public(main/0).
:- mode(main, one).
:- info(main/0, [
comment is 'Starts iteractive command language interpreter.']).
:- private(booked/2).
:- dynamic(booked/2).
:- mode(booked(?atom, ?atom), zero_or_more).
:- info(booked/2, [
comment is 'Booked places in flight.',
argnames is ['Passenger', 'Flight']]).
main :-
write('Fly Amzi! Air'), nl,
repeat,
do_command(Command),
Command == exit.
do_command(Command) :-
write('enter command> '),
read_tokens(Tokens),
phrase(command(List), Tokens),
Command =.. List,
call(Command),
!.
read_tokens(Tokens) :-
read_codes(Codes),
codes_to_tokens(Codes, Tokens).
read_codes(Codes) :-
get_code(Code),
read_codes(Code, Codes).
read_codes(10, [[]]) :-
!.
read_codes(13, [[]]) :-
!.
read_codes(32, [[]| Rest]) :-
!, read_codes(Rest).
read_codes(Code, [[Code| Codes]| Rest]) :-
read_codes([Codes| Rest]).
codes_to_tokens([], []).
codes_to_tokens([List| Lists], [Token| Tokens]) :-
atom_codes(Token, List),
codes_to_tokens(Lists, Tokens).
command([Op| Args]) --> operation(Op), arguments(Args).
arguments([Arg| Args]) --> argument(Arg), arguments(Args).
arguments([]) --> [].
operation(report) --> [list].
operation(book) --> [book].
operation(exit) --> ([exit]; [quit]; [bye]).
argument(passengers) --> [passengers].
argument(flights) --> [flights].
argument(Flight) --> [Flight], {flight(Flight)}.
argument(Passenger) --> [Passenger].
flight(aa101).
flight(aa102).
flight(aa103).
report(flights) :-
flight(Flight),
write(Flight), nl,
fail.
report(_).
report(passengers, Flight) :-
booked(Passenger, Flight),
write(Passenger), nl,
fail.
report(_, _).
book(Passenger, Flight) :-
assertz(booked(Passenger, Flight)).
exit.
:- end_object.
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