How to repair error in Einstein Zebra in prolog > - prolog

I have a problem with zebra puzzle.
rightOf(A,B,(B,A,_,_,_)).
rightOf(A,B,(_,B,A,_,_)).
rightOf(A,B,(_,_,B,A,_)).
rightOf(A,B,(_,_,_,B,A)).
middleHouse(A,(_,_,A,_,_)).
firstHouse(A,(A,_,_,_,_)).
nextTo(A,B,(A,B,_,_,_)).
nextTo(A,B,(_,A,B,_,_)).
nextTo(A,B,(_,_,A,B,_)).
nextTo(A,B,(_,_,_,A,B)).
nextTo(A,B,(B,A,_,_,_)).
nextTo(A,B,(_,B,A,_,_)).
nextTo(A,B,(_,_,B,A,_)).
nextTo(A,B,(_,_,_,B,A)).
house[Nationality,Pet,Sport,Drinks,Colour].
zebra_owner(Owner) :-
houses(Houses),
exists(house(Owner,zebra,_,_,_), Houses).
length(5,Houses),
exists(house(british,_,_,_,red),Houses),
exists(house(spanish,dog,_,_,_),Houses),
exists(house(_,_,_,coffe,green),Houses),
exists(house(ukrainian,_,_,tea,_),Houses),
rightOf(house(_,_,_,_,green),house(_,_,_,_,ivory),Houses),
exists(house(_,snail,tennis,_,_),Houses),
exists(house(_,_,chess,_,yellow),Houses),
middleHouse(house(_,_,_,mlik,_),Houses),
firstHouse(house(norwegian,_,_,_,_),Houses),
nextTo(house(_,_,rugby,_,_),house(_,fox,_,_,_),Houses),
nextTo(house(_,_,chess,_,_),house(_,horse,_,_,_),Houses),
exists(house(_,_,volleyball,orangejuice,_),Houses),
exists(house(japanese,_,_,_,_),Houses),
nextTo(house(norwegian,_,_,_,_),house(_,_,_,_,blue),Houses),
nextTo(house(_,_,_,tea,_),house(_,_,_,milo,_),Houses),
exists(house(zebra_owner,zebra,_,_,_),Houses).
Under
house[Nationality,Pet,Smokes,Drinks,Colour].
I see the error: Singleton variables: house[Nationality,Pet,Smokes,Drinks,Colour].
And when I write ?- zebra_owner(Owner)
I see the error: procedure 'houses(A)' does not exist. Reachable from:zebra_owner(A).`


You cannot write
house[Nationality,Pet,Sport,Drinks,Colour].
that's non-existent syntax.
To express that predicate house/1 is valid for list [Nationality,Pet,Sport,Drinks,Colour], write:
house([Nationality,Pet,Sport,Drinks,Colour]).
You also must pay attention to predicate naming: houses/1 is not house/1. Predicate houses/1 is defined nowhere (the error message is wrong, it should really say predicate houses/1 is undeclared).

Related

Problem with building an expert system in prolog

I keep getting syntax errors while compiling this code in prolog. I'm new to programming so I don't quite understand. Can someone please help me debug where I went wrong? The expert system was meant to classify animals with vertebrates and invertebrates. This is the code I currently have:
:-dynamic known/3
top_goal(X):-animal(X).
%Animals and their classifications
animal(lion):-
type(vertebrate),
color(brown).
animal(bee):-
type(invertebrate),
color(yellow).
animal(crickets):-
type(invertebrate),
color(green).
%background information about vertebrates and invertebrates.
animal(vertebrate):-
vertebral_column(present),
nerve_cord(dorsal_and_hollow),
skeleton(internal),
heart(located_on_right_side),
haemoglobin(present_in_red_blood_cells).
animal(invertebrate):-
vertebral_column(absent),
skeleton(external),
heart(located_on_dorsal_side),
haemoglobin(dissolved_in_plasma).
%Ask rules
animal(X):-ask(type,X).
animal(X):-ask(color,X).
animal(X):-ask(sound,X).
ask(A,V):-
write(A:V),%ask user
write('?:'),
read(Y),%get the answer
asserta(known(Y,A,V),%remember it
Y==yes.%succeed or fail
solve:-
retractall(known(_,_,)),
top_goal(X),
write('The animal is '),write(X),nl.
solve:-
write('This animal is unknown '),nl.

You have some typos.
ask(A,V):-
write(A:V),%ask user
write('?:'),
read(Y),%get the answer
asserta(known(Y,A,V)), %remember it ***missing ')'
Y==yes.%succeed or fail
and here
solve:-
retractall(known(_,_,_)), % *** missing _
top_goal(X),
write('The animal is '),write(X),nl.
Then some codes are missing: color/1, haemoglobin/1, heart/1,
nerve_cord/1, skeleton/1, top_goal/1, type/1, vertebral_column/1.

CHR in SWI Prolog: Rule guard containing "just removed" constraint does not return, blows stack

A little test code with no particular meaning:
:- use_module(library(chr)).
:- chr_constraint foo/1, bar/1, anyone/2.
foo(X) \ bar(Y) <=> anyone(X,Y).
anyone(_,Y) <=> bar(Y) | writef("bar(%w) exists\n",[Y]).
anyone(_,Y) <=> writef("bar(%w) does not exist\n",[Y]).
If the above is consulted from the SWI Prolog command line and then run with:
?- foo(8),bar(10).
there is overflow after some time:
Could not reenable global-stack
Could not reenable global-stack
ERROR: Out of global-stack.
ERROR: No room for exception term. Aborting.
Could not reenable global-stack
ERROR: Out of global-stack.
ERROR: No room for exception term. Aborting.
ERROR: Execution Aborted
% Execution Aborted
However, if the code for the second rule is changed by moving the test for bar from the guard ot the head:
:- use_module(library(chr)).
:- chr_constraint foo/1, bar/1, anyone/2.
foo(X) \ bar(Y) <=> anyone(X,Y).
anyone(_,Y),bar(Y) <=> writef("bar(%w) exists\n",[Y]). % changed!
anyone(_,Y) <=> writef("bar(%w) does not exist\n",[Y]).
then execution terminates:
?- foo(8),bar(10).
bar(10) does not exist
foo(8).
Is this an accident of the implementation? It does seem a bit dicey.
Furthermore, the above code was written because I wanted to test whether the constraint to be removed from the store (here, bar(Y)) would be available in the body of the rule. Apparently not, it is already gone when the rule body executes; but is this implementation dependent or a necessary or specified behaviour of CHR?

how to solve the error in this prolog code

What is wrong in this code
frequency(f1).
frequency(f2).
frequency(f3).
allocation(z1,z2,z3,z4,z5,z6,z7,z8) :-
frequency(z1), frequency(z2), frequency(z3), frequency(z4), frequency(z5), frequency(z6), frequency(z7), frequency(z8),
z1\==z2, z1\==z3, z2\==z4, z2\==z3, z3\==z4, z3\==z6, z4\==z5, z4\==z6, z4\==z7, z6\==z7, z6\==z8.
?- allocation(f1,f2,f3,f1,f2,f3,f2,f3).
syntax error: . or operator expected after expression

The following code highlighting should make it clear why the goal allocation(f1,f2,f3,f1,f2,f3,f2,f3) cannot succeed:
allocation(Z1,Z2,Z3,Z4,Z5,Z6,Z7,Z8) :-
dif(Z1,Z2), dif(Z1,Z3),
dif(Z2,Z3), dif(Z2,Z4),
dif(Z3,Z4), dif(Z3,Z6),
dif(Z4,Z5), dif(Z4,Z6), dif(Z4,Z7),
dif(Z6,Z7), dif(Z6,Z8),
maplist(frequency, [Z1,Z2,Z3,Z4,Z5,Z6,Z7,Z8]).
Note the use of dif/2 instead of (\==)/2 in the code above?
prolog-dif preserves logical-purity, for easier debugging!

I am not sure as to why 'find_identity(X)' is returning as false [Code Below]

Snippets of my code are shown below. After doing a lot of cumbersome tracing, I have reached a point where I think it's the external modules which are the source of my problem, as the findall in links_of_actor never gets called, but links_of_actor itself gets called. I would be very grateful to anyone who can help and can clarify/add more of my code to this question if needed.
find_identity(A) :-
all_actor_links(ALs),
find_identity(ALs,[],A).
find_identity([a(A,_)],_,A).
find_identity(ALs,Ms,A) :-
agent_ask_oracle(oscar,o(1),link,L),
( memberchk(L,Ms) -> find_identity(ALs,Ms,A)
; otherwise -> purge_actors(ALs,L,NewALs),
find_identity(NewALs,[L|Ms],A)
).
links_of_actor(A,Ls) :-
actor(A),
wp(A,WT),
findall(L,wt_link(WT,L),Ls1),
findall(L,link(L),Ls2),
intersection(Ls1,Ls2,Ls).
actor_links(A,a(A,Ls)) :-
links_of_actor(A,Ls).
all_actor_links(ALs) :-
findall(A,actor(A),As),
maplist(actor_links,As,ALs).
----------------------------------------------------- Support Functions ---------------------------------------------------
% wp(Q,WT) <- issue query Q to Wikipedia and return the page in wikitext format
wp(Q,WT):-
wp_cache(Q,WT),!.
wp(Q,WT):-
wp_query2URL(Q,URL),
http_get(URL,R,[]),
atom_json_term(R,RR,[]),
wt_get(RR,WT0),
( atomic_list_concat1(_L,'#REDIRECT',WT0) -> wt_link(WT0,QQ),wp(QQ,WT)
; otherwise -> WT=WT0
),
assert(wp_cache(Q,WT)).
------------------------------------------------------------ Edit ----------------------------------------------------------------
After using the guitracer that is available with prolog, I have found that the program fails at http_get(URL,R,[]) in the wp(Q,WT) predicate. However, I am still not sure as to why this isn't working - Could it be possibly because of my internet?
To clarify, the predicate actor is defined in my file: actor('Billy Bob Thornton'). etc. and so are the links : link('Barack Obama')..

Using these definitions, the error can be localized by adding a # in front of those goals that have to succeed.
...
wp(Q,WT):-
#wp_query2URL(Q,URL),
#http_get(URL,R,[]),
#atom_json_term(R,RR,[]),
#wt_get(RR,WT0),
...

Well, did you try to see if the URL you gave to http_open is actually valid? You can always test from the top-level if you can http_open an URL:
?- use_module(library(http/http_client)).
true.
?- http_open("stackoverflow.com", R, []).
R = % a lot of stuff

prolog get syntax error when increase stack size

Trying to solve the puzzle task with prolog and got some problems.
1002 Stack Overflow. Re-configure with Setup if necessary.
So, I've tried to increase stack size in setup and run program again.
But it causes the other error: Syntax error on line...
The error line is line with operator "not" in predicate.
Here is my code:
domains
age = integer
childname,ffood,fear = string
child = child(childname,age,ffood,fear)
children = child*
predicates
solve
name(child,childname)
fear(child,fear)
age(child,age)
ffood(child,ffood)
keys(children)
solution(children)
elder(child)
member(children,child)
structure(children)
clauses
member([X|_],X).
member([_|SP],X):-member(SP,X).
name(child(A,_,_,_),A).
age(child(_,A,_,_),A).
ffood(child(_,_,A,_),A).
fear(child(_,_,_,A),A).
structure([child("Dima",_,_,_),child("Kate",_,_,_),child("Misha",_,_,_),child("Sveta",_,_,_),child("Ura",_,_,_)]).
elder(child(_,A,_,_)):-A=7;A=8.
solve:-structure(Children),keys(Children),solution(Children).
keys(Struct):-
member(Struct,child(_,4,_,_)),
member(Struct,child(_,5,_,_)),
member(Struct,child(_,6,_,_),
member(Struct,child(_,7,_,_),
member(Struct,child(_,8,_,_)),
member(Struct,child(_,_,"Banana",_),
member(Struct,child(_,_,"Icecream",_),
member(Struct,child(_,_,"Pizza",_),
member(Struct,child(_,_,"Pasta",_),
member(Struct,child(_,_,"Chocolate",_),
member(Struct,child(_,_,_,"Thunderstorm"),
member(Struct,child(_,_,_,"Spiders"),
member(Struct,child(_,_,_,"Ghosts"),
member(Struct,child(_,_,_,"Dogs"),
member(Struct,child(_,_,_,"Darkness"),
member(Struct,Child1),
name(Child1,"Kate"),
elder(Child1),
not(fear(Child1,"Darkness")),
not(ffood(Child1,"Chocolate")),
member(Struct,Child2),
name(Child2,"Sveta"),
elder(Child2),
not(fear(Child2,"Darkness")),
not(ffood(Child2,"Chocolate")),
ffood(Child2,"Pizza"),
not(fear(Child2,"Spiders")),
member(Struct,Child3),
age(Child3,5),
fear(Child3,"Ghosts"),
member(Struct,Child4),
age(Child4,6),
fear(Child4,"Thunderstorm"),
not(ffood(Child4,"Chocolate")),
not(ffood(Child4,"Pasta")),
member(Struct,Child5),
age(Child5,4),
ffood(Child5,"Banana"),
member(Struct,Child6),
age(Child6,8),
not(fear(Child6,"Dogs")),
member(Struct,Child7),
name(Child7,"Dima"),
not(age(Child7,5)),
not(fear(Child7,"Darkness")),
not(fear(Child7,"Spiders")),
not(ffood(Child7,"Banana")),
member(Struct,Child8),
name(Child8,"Misha"),
not(fear(Child8,"Darkness")),
not(fear(Child8,"Spiders")),
not(ffood(Child8,"Banana")).
solution (Children):-
write ("Solve:"), write (Children).
goal
solve.
Found strange this prolog behavior... maybe somebody had the same problem?

I tried to reformat your code with SWI-Prolog:
keys(Struct):-
member(Struct,child(_,4,_,_)),
member(Struct,child(_,5,_,_)),
member(Struct,child(_,6,_,_),
member(Struct,child(_,7,_,_),
member(Struct,child(_,8,_,_)),
member(Struct,child(_,_,"Banana",_),
...
seems you're missing some parenthesis...
after the obvious correction, I get
?- solve.
Solve:[child(Dima,6,Icecream,Thunderstorm),child(Kate,8,Pasta,Spiders),child(Misha,5,Chocolate,Ghosts),child(Sveta,7,Pizza,Dogs),child(Ura,4,Banana,Darkness)]
true .

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