Definite Clasue Grammer(DCG)，把连接符:-替换成为–>，这种表达形式由Prolog翻译成为普通的差异表形式。
使用DCG，原来的句子谓词将写为：
sentence –> nounphrase, verbphrase.
这个句子将被翻译成一般的使用差异表的Prolog子句，但是这里不再用“-”隔开，而是变成了两个参数，上面的这个句子与下面的Prolog子句等价。
sentence(S1, S2):-
nounphrase(S1, S3),
verbphrase(S3, S2).
find nani 的最终版本
% NANI SEARCH - A sample adventure game
% Nani Search is designed to illustrate Prolog programming. It
% is an implementation of the principle example used in
% this tutorial.
main:- nani_search. % main entry point
nani_search:-
init_dynamic_facts, % predicates which are not compiled
write('NANI SEARCH - A Sample Adventure Game'),nl,
write('Copyright (C) Amzi! inc. 1990-2010'),nl,
write('No rights reserved, use it as you wish'),nl,
nl,
write('Nani Search is designed to illustrate Prolog programming.'),nl,
write('As such, it might be the simplest adventure game. The game'),nl,
write('is the primary example used in this tutorial.'),nl,
write('Full source is included as well.'),nl,
nl,
write('Your persona as the adventurer is that of a three year'),nl,
write('old. The Nani is your security blanket. It is getting'),nl,
write('late and you''re tired, but you can''t go to sleep'),nl,
write('without your Nani. Your mission is to find the Nani.'),nl,
nl,
write('You control the game by using simple English commands'),nl,
write('expressing the action you wish to take. You can go to'),nl,
write('other rooms, look at your surroundings, look in things'),nl,
write('take things, drop things, eat things, inventory the'),nl,
write('things you have, and turn things on and off.'),nl,
nl,
write('Hit any key to continue.'),get0(_),
write('Type "help" if you need more help on mechanics.'),nl,
write('Type "hint" if you want a big hint.'),nl,
write('Type "quit" if you give up.'),nl,
nl,
write('Enjoy the hunt.'),nl,
look, % give a look before starting the game
command_loop.
% command_loop - repeats until either the nani is found or the
% player types quit
command_loop:-
repeat,
get_command(X),
do(X),
(nanifound; X == quit).
% do - matches the input command with the predicate which carries out
% the command. More general approaches which might work in the
% listener are not supported in the compiler. This approach
% also gives tighter control over the allowable commands.
% The cuts prevent the forced failure at the end of "command_loop"
% from backtracking into the command predicates.
do(goto(X)):-goto(X),!.
do(nshelp):-nshelp,!.
do(hint):-hint,!.
do(inventory):-inventory,!.
do(take(X)):-take(X),!.
do(drop(X)):-drop(X),!.
do(eat(X)):-eat(X),!.
do(look):-look,!.
do(turn_on(X)):-turn_on(X),!.
do(turn_off(X)):-turn_off(X),!.
do(look_in(X)):-look_in(X),!.
do(quit):-quit,!.
% These are the predicates which control exit from the game. If
% the player has taken the nani, then the call to "have(nani)" will
% succeed and the command_loop will complete. Otherwise it fails
% and command_loop will repeat.
nanifound:-
have(nani),
write('Congratulations, you saved the Nani.'),nl,
write('Now you can rest secure.'),nl,nl.
quit:-
write('Giving up? It''s going to be a scary night'),nl,
write('and when you get the Nani it''s not going'),nl,
write('to smell right.'),nl,nl.
% The help command
nshelp:-
write('Use simple English sentences to enter commands.'),nl,
write('The commands can cause you to:'),nl,
nl,
write(' go to a room (ex. go to the office)'),nl,
write(' look around (ex. look)'),nl,
write(' look in something (ex. look in the desk)'),nl,
write(' take something (ex. take the apple)'),nl,
write(' drop something (ex. drop the apple)'),nl,
write(' eat something (ex. eat the apple)'),nl,
write(' turn something on (ex. turn on the light)'),nl,
write(' inventory your things (ex. inventory)'),nl,
nl,
write('The examples are verbose, terser commands and synonyms'),nl,
write('are usually accepted.'),nl,nl,
write('Hit any key to continue.'),nl,
get0(_),
look.
hint:-
write('You need to get to the cellar, and you can''t unless'),nl,
write('you get some light. You can''t turn on the cellar'),nl,
write('light, but there is a flash light in the desk in the'),nl,
write('office you might use.'),nl,nl,
look.
% Initial facts describing the world. Rooms and doors do not change,
% so they are compiled.
room(office).
room(kitchen).
room('dining room').
room(hall).
room(cellar).
door(office,hall).
door(hall,'dining room').
door('dining room',kitchen).
door(kitchen,cellar).
door(kitchen,office).
connect(X,Y):-
door(X,Y).
connect(X,Y):-
door(Y,X).
% These facts are all subject to change during the game, so rather
% than being compiled, they are "asserted" to the listener at
% run time. This predicate is called when "nanisrch" starts up.
init_dynamic_facts:-
assertz(location(desk,office)),
assertz(location(apple,kitchen)),
assertz(location(flashlight,desk)),
assertz(location('washing machine',cellar)),
assertz(location(nani,'washing machine')),
assertz(location(table,kitchen)),
assertz(location(crackers,desk)),
assertz(location(broccoli,kitchen)),
assertz(here(kitchen)),
assertz(turned_off(flashlight)),
assertz(turned_on(workaround)), %workaround under swiprolog
retract(turned_on(workaround)),
assertz(have(workaround)), %workaround under swiprolog
retract(have(workaround)).
furniture(desk).
furniture('washing machine').
furniture(table).
edible(apple).
edible(crackers).
tastes_yuchy(broccoli).
%%%%%%%% COMMANDS %%%%%%%%%%%%%%%%%%%%%%%%%%
% goto moves the player from room to room.
goto(Room):-
can_go(Room), % check for legal move
puzzle(goto(Room)), % check for special conditions
moveto(Room), % go there and tell the player
look.
goto(_):- look.
can_go(Room):- % if there is a connection it
here(Here), % is a legal move.
connect(Here,Room),!.
can_go(Room):-
respond(['You can''t get to ',Room,' from here']),fail.
moveto(Room):- % update the logicbase with the
retract(here(_)), % new room
asserta(here(Room)).
% look lists the things in a room, and the connections
look:-
here(Here),
respond(['You are in the ',Here]),
write('You can see the following things:'),nl,
list_things(Here),
write('You can go to the following rooms:'),nl,
list_connections(Here).
list_things(Place):-
location(X,Place),
tab(2),write(X),nl,
fail.
list_things(_).
list_connections(Place):-
connect(Place,X),
tab(2),write(X),nl,
fail.
list_connections(_).
% look_in allows the player to look inside a thing which might
% contain other things
look_in(Thing):-
location(_,Thing), % make sure there's at least one
write('The '),write(Thing),write(' contains:'),nl,
list_things(Thing).
look_in(Thing):-
respond(['There is nothing in the ',Thing]).
% take allows the player to take something. As long as the thing is
% contained in the room it can be taken, even if the adventurer hasn't
% looked in the the container which contains it. Also the thing
% must not be furniture.
take(Thing):-
is_here(Thing),
is_takable(Thing),
move(Thing,have),
respond(['You now have the ',Thing]).
is_here(Thing):-
here(Here),
contains(Thing,Here),!. % don't backtrack
is_here(Thing):-
respond(['There is no ',Thing,' here']),
fail.
contains(Thing,Here):- % recursive definition to find
location(Thing,Here). % things contained in things etc.
contains(Thing,Here):-
location(Thing,X),
contains(X,Here).
is_takable(Thing):- % you can't take the furniture
furniture(Thing),
respond(['You can''t pick up a ',Thing]),
!,fail.
is_takable(_). % not furniture, ok to take
move(Thing,have):-
retract(location(Thing,_)), % take it from its old place
asserta(have(Thing)). % and add to your possessions
% drop - allows the player to transfer a possession to a room
drop(Thing):-
have(Thing), % you must have the thing to drop it
here(Here), % where are we
retract(have(Thing)),
asserta(location(Thing,Here)).
drop(Thing):-
respond(['You don''t have the ',Thing]).
% eat, because every adventure game lets you eat stuff.
eat(Thing):-
have(Thing),
eat2(Thing).
eat(Thing):-
respond(['You don''t have the ',Thing]).
eat2(Thing):-
edible(Thing),
retract(have(Thing)),
respond(['That ',Thing,' was good']).
eat2(Thing):-
tastes_yuchy(Thing),
respond(['Three year olds don''t eat ',Thing]).
eat2(Thing):-
respond(['You can''t eat a ',Thing]).
% inventory list your possesions
inventory:-
have(X), % make sure you have at least one thing
write('You have: '),nl,
list_possessions.
inventory:-
write('You have nothing'),nl.
list_possessions:-
have(X),
tab(2),write(X),nl,
fail.
list_possessions.
% turn_on recognizes two cases. If the player tries to simply turn
% on the light, it is assumed this is the room light, and the
% appropriate error message is issued. Otherwise turn_on has to
% refer to an object which is turned_off.
turn_on(light):-
respond(['You can''t reach the switch and there''s nothing to stand on']).
turn_on(Thing):-
have(Thing),
turn_on2(Thing).
turn_on(Thing):-
respond(['You don''t have the ',Thing]).
turn_on2(Thing):-
turned_on(Thing),
respond([Thing,' is already on']).
turn_on2(Thing):-
turned_off(Thing),
retract(turned_off(Thing)),
asserta(turned_on(Thing)),
respond([Thing,' turned on']).
turn_on2(Thing):-
respond(['You can''t turn a ',Thing,' on']).
% turn_off - I didn't feel like implementing turn_off （作者好任性啊）
turn_off(Thing):-
respond(['I lied about being able to turn things off']).
% The only special puzzle in Nani Search has to do with going to the
% cellar. Puzzle is only called from goto for this reason. Other
% puzzles pertaining to other commands could easily be added.
puzzle(goto(cellar)):-
have(flashlight),
turned_on(flashlight),!.
puzzle(goto(cellar)):-
write('You can''t go to the cellar because it''s dark in the'),nl,
write('cellar, and you''re afraid of the dark.'),nl,
!,fail.
puzzle(_).
% respond simplifies writing a mixture of literals and variables
respond([]):-
write('.'),nl,nl.
respond([H|T]):-
write(H),
respond(T).
% Simple English command listener. It does some semantic checking
% and allows for various synonyms. Within a restricted subset of
% English, a command can be phrased many ways. Also non grammatical
% constructs are understood, for example just giving a room name
% is interpreted as the command to goto that room.
% Some interpretation is based on the situation. Notice that when
% the player says turn on the light it is ambiguous. It could mean
% the room light (which can't be turned on in the game) or the
% flash light. If the player has the flash light it is interpreted
% as flash light, otherwise it is interpreted as room light.
get_command(C):-
readlist(L), % reads a sentence and puts [it,in,list,form]
command(X,L,[]), % call the grammar for command
C =.. X,!. % make the command list a structure
get_command(_):-
respond(['I don''t understand, try again or type help']),fail.
% The grammar doesn't have to be real English. There are two
% types of commands in Nani Search, those with and without a
% single argument. A special case is also made for the command
% goto which can be activated by simply giving a room name.
command([Pred,Arg]) --> verb(Type,Pred),nounphrase(Type,Arg).
command([Pred]) --> verb(intran,Pred).
command([goto,Arg]) --> noun(go_place,Arg).
% Recognize three types of verbs. Each verb corresponds to a command,
% but there are many synonyms allowed. For example the command
% turn_on will be triggered by either "turn on" or "switch on".
verb(go_place,goto) --> go_verb.
verb(thing,V) --> tran_verb(V).
verb(intran,V) --> intran_verb(V).
go_verb --> [go].
go_verb --> [go,to].
go_verb --> [g].
tran_verb(take) --> [take].
tran_verb(take) --> [pick,up].
tran_verb(drop) --> [drop].
tran_verb(drop) --> [put].
tran_verb(drop) --> [put,down].
tran_verb(eat) --> [eat].
tran_verb(turn_on) --> [turn,on].
tran_verb(turn_on) --> [switch,on].
tran_verb(turn_off) --> [turn,off].
tran_verb(look_in) --> [look,in].
tran_verb(look_in) --> [look].
tran_verb(look_in) --> [open].
intran_verb(inventory) --> [inventory].
intran_verb(inventory) --> [i].
intran_verb(look) --> [look].
intran_verb(look) --> [look,around].
intran_verb(look) --> [l].
intran_verb(quit) --> [quit].
intran_verb(quit) --> [exit].
intran_verb(quit) --> [end].
intran_verb(quit) --> [bye].
intran_verb(nshelp) --> [help].
intran_verb(hint) --> [hint].
% a noun phrase is just a noun with an optional determiner in front.
nounphrase(Type,Noun) --> det,noun(Type,Noun).
nounphrase(Type,Noun) --> noun(Type,Noun).
det --> [the].
det --> [a].
% Nouns are defined as rooms, or things located somewhere. We define
% special cases for those things represented in Nani Search by two
% words. We can't expect the user to type the name in quotes.
noun(go_place,R) --> [R], {room(R)}.
noun(go_place,'dining room') --> [dining,room].
noun(thing,T) --> [T], {location(T,_)}.
noun(thing,T) --> [T], {have(T)}.
noun(thing,flashlight) --> [flash,light].
noun(thing,'washing machine') --> [washing,machine].
noun(thing,'dirty clothes') --> [dirty,clothes].
% If the player has just typed light, it can be interpreted three ways.
% If a room name is before it, it must be a room light. If the
% player has the flash light, assume it means the flash light. Otherwise
% assume it is the room light.
noun(thing,light) --> [X,light], {room(X)}.
noun(thing,flashlight) --> [light], {have(flashlight)}.
noun(thing,light) --> [light].
% readlist - read a list of words, based on a Clocksin & Mellish
% example.
readlist(L):-
write('> '),
read_word_list(L).
read_word_list([W|Ws]) :-
get0(C),
readword(C, W, C1), % Read word starting with C, C1 is first new
restsent(C1, Ws), !. % character - use it to get rest of sentence
restsent(C,[]) :- lastword(C), !. % Nothing left if hit last-word marker
restsent(C,[W1|Ws]) :-
readword(C,W1,C1), % Else read next word and rest of sentence
restsent(C1,Ws).
readword(C,W,C1) :- % Some words are single characters
single_char(C), % i.e. punctuation
!,
name(W, [C]), % get as an atom
get0(C1).
readword(C, W, C1) :-
is_num(C), % if we have a number --
!,
number_word(C, W, C1, _). % convert it to a genuine number
readword(C,W,C2) :- % otherwise if character does not
in_word(C, NewC), % delineate end of word - keep
get0(C1), % accumulating them until
restword(C1,Cs,C2), % we have all the word
name(W, [NewC|Cs]). % then make it an atom
readword(C,W,C2) :- % otherwise
get0(C1),
readword(C1,W,C2). % start a new word
restword(C, [NewC|Cs], C2) :-
in_word(C, NewC),
get0(C1),
restword(C1, Cs, C2).
restword(C, [], C).
single_char(0',).
single_char(0';).
single_char(0':).
single_char(0'?).
single_char(0'!).
single_char(0'.).
in_word(C, C) :- C >= 0'a, C =< 0'z.
in_word(C, L) :- C >= 0'A, C =< 0'Z, L is C + 32.
in_word(0'',0'').
in_word(0'-,0'-).
% Have character C (known integer) - keep reading integers and build
% up the number until we hit a non-integer. Return this in C1,
% and return the computed number in W.
number_word(C, W, C1, Pow10) :-
is_num(C),
!,
get0(C2),
number_word(C2, W1, C1, P10),
Pow10 is P10 * 10,
W is integer(((C - 0'0) * Pow10) + W1).
number_word(C, 0, C, 0.1).
is_num(C) :-
C =< 0'9,
C >= 0'0.
% These symbols delineate end of sentence
lastword(10). % end if new line entered
lastword(0'.).
lastword(0'!).
lastword(0'?).
我们可以试一下
?- nani_search(). NANI SEARCH - A Sample Adventure Game Copyright (C) Amzi! inc. 1990-2010 No rights reserved, use it as you wish Nani Search is designed to illustrate Prolog programming. As such, it might be the simplest adventure game. The game is the primary example used in this tutorial. Full source is included as well. Your persona as the adventurer is that of a three year old. The Nani is your security blanket. It is getting late and you're tired, but you can't go to sleep without your Nani. Your mission is to find the Nani. You control the game by using simple English commands expressing the action you wish to take. You can go to other rooms, look at your surroundings, look in things take things, drop things, eat things, inventory the things you have, and turn things on and off. Hit any key to continue. Type "help" if you need more help on mechanics. Type "hint" if you want a big hint. Type "quit" if you give up. Enjoy the hunt. You are in the kitchen. You can see the following things: apple table broccoli You can go to the following rooms: cellar office dining room > help Use simple English sentences to enter commands. The commands can cause you to: go to a room (ex. go to the office) look around (ex. look) look in something (ex. look in the desk) take something (ex. take the apple) drop something (ex. drop the apple) eat something (ex. eat the apple) turn something on (ex. turn on the light) inventory your things (ex. inventory) The examples are verbose, terser commands and synonyms are usually accepted. Hit any key to continue. |: You are in the kitchen. You can see the following things: apple table broccoli You can go to the following rooms: cellar office dining room > take the apple You now have the apple. > go to the office You are in the office. You can see the following things: desk You can go to the following rooms: hall kitchen > look in the desk The desk contains: flashlight crackers > take the crackers You now have the crackers. > take the flashlight You now have the flashlight. >turn on the flashlight flashlight turned on. > go to the kitchen You are in the kitchen. You can see the following things: table broccoli You can go to the following rooms: cellar office dining room > eat the apple That apple was good. > eat the crackers That crackers was good. > go to the cellar You are in the cellar. You can see the following things: washing machine You can go to the following rooms: kitchen look in the washing machine The washing machine contains: nani > take nani You now have the nani. Congratulations, you saved the Nani. Now you can rest secure. true .