Undefined Procedure Help

[Sigismo]

Hey,
Im trying for days to figure out why i get this error:

ERROR: ask/2: Undefined procedure: known/3
   Exception: (11) ask(nostrils, external_tubular) ? Unknown option (h for help)
   Exception: (11) ask(nostrils, external_tubular) ? creep
   Exception: (7) bird(_G229) ? creep

Thanks for the assistance in advance.

bird(whistling_swan) :- family(swan), voice(muffled_musical_whistle).
bird(canada_goose):- family(goose), season(winter), country(united_states), head(black), cheek(white).
bird(canada_goose):- family(goose), season(summer), country(canada),head(black), cheek(white).
bird(trumpeter_swan) :- family(swan), voice(loud_trumpeting).
bird(laysan_albatross):- family(albatross), color(white).
bird(black_footed_albatross):- family(albatross), color(dark).

order(tubenose) :- nostrils(external_tubular) ,live(at_sea), bill(hooked).
order(waterfowl) :- feet(webbed), bill(flat).

family(albatross) :- order(tubenose), size(large), wings(long_narrow).
family(swan) :- order(waterfowl), neck(long), color(white), flight(ponderous).


nostrils(X):- ask(nostrils, X).
live(X):- ask(live, X).
bill(X) :- ask(bill, X).
wings(X):- ask(wings, X).
neck(X):- ask(neck, X).
size(X) :- ask(size,X).
color(X):- ask(color, X).
feet(X):- ask(feet, X).
flight(X):- ask(flight,X).
voice(X):- ask(voice,X).


ask(A, V):- known(yes, A, V), !.
ask(A, V):- known(_, A, V),!,fail.
ask(A, V):- write(A:V), write('? : '),read(Y),asserta(known(Y, A, V)),  Y == yes.

[Paulo Moura]

On 2009/10/19, at 00:14, Sigismo wrote:

> Hey,
> Im trying for days to figure out why i get this error:
>
> ERROR: ask/2: Undefined procedure: known/3
>   Exception: (11) ask(nostrils, external_tubular) ? Unknown option  
> (h for
> help)
>   Exception: (11) ask(nostrils, external_tubular) ? creep
>   Exception: (7) bird(_G229) ? creep
>
> Thanks for the assistance in advance.
>
> bird(whistling_swan) :- family(swan), voice(muffled_musical_whistle).
> bird(canada_goose):- family(goose), season(winter),  
> country(united_states),
> head(black), cheek(white).
> bird(canada_goose):- family(goose), season(summer),
> country(canada),head(black), cheek(white).
> bird(trumpeter_swan) :- family(swan), voice(loud_trumpeting).
> bird(laysan_albatross):- family(albatross), color(white).
> bird(black_footed_albatross):- family(albatross), color(dark).
>
> order(tubenose) :- nostrils(external_tubular) ,live(at_sea),  
> bill(hooked).
> order(waterfowl) :- feet(webbed), bill(flat).
>
> family(albatross) :- order(tubenose), size(large), wings(long_narrow).
> family(swan) :- order(waterfowl), neck(long), color(white),
> flight(ponderous).
>
>
> nostrils(X):- ask(nostrils, X).
> live(X):- ask(live, X).
> bill(X) :- ask(bill, X).
> wings(X):- ask(wings, X).
> neck(X):- ask(neck, X).
> size(X) :- ask(size,X).
> color(X):- ask(color, X).
> feet(X):- ask(feet, X).
> flight(X):- ask(flight,X).
> voice(X):- ask(voice,X).
>
>
> ask(A, V):- known(yes, A, V), !.
> ask(A, V):- known(_, A, V),!,fail.
> ask(A, V):- write(A:V), write('? : '),read(Y),asserta(known(Y, A,  
> V)),  Y ==
> yes.

Add to your program the directive:

:- dynamic(known/3).

Cheers,

Paulo


-----------------------------------------------------------------
Paulo Jorge Lopes de Moura, PhD
Assistant Professor
Dep. of Computer Science, University of Beira Interior
6201-001 Covilhã, Portugal

Office 3.18  Ext. 3276
Phone: [phone] Fax: [phone]
Email: <mailto:pmoura@...>

Home page: <http://www.di.ubi.pt/~pmoura>
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[Sigismo]

Thanks it works but as ":-dynamic known/3". Im wondering why it would behave like that without the directive?

Paulo Moura wrote:

On 2009/10/19, at 00:14, Sigismo wrote:

> Hey,
> Im trying for days to figure out why i get this error:
>
> ERROR: ask/2: Undefined procedure: known/3
>   Exception: (11) ask(nostrils, external_tubular) ? Unknown option  
> (h for
> help)
>   Exception: (11) ask(nostrils, external_tubular) ? creep
>   Exception: (7) bird(_G229) ? creep
>
> Thanks for the assistance in advance.
>
> bird(whistling_swan) :- family(swan), voice(muffled_musical_whistle).
> bird(canada_goose):- family(goose), season(winter),  
> country(united_states),
> head(black), cheek(white).
> bird(canada_goose):- family(goose), season(summer),
> country(canada),head(black), cheek(white).
> bird(trumpeter_swan) :- family(swan), voice(loud_trumpeting).
> bird(laysan_albatross):- family(albatross), color(white).
> bird(black_footed_albatross):- family(albatross), color(dark).
>
> order(tubenose) :- nostrils(external_tubular) ,live(at_sea),  
> bill(hooked).
> order(waterfowl) :- feet(webbed), bill(flat).
>
> family(albatross) :- order(tubenose), size(large), wings(long_narrow).
> family(swan) :- order(waterfowl), neck(long), color(white),
> flight(ponderous).
>
>
> nostrils(X):- ask(nostrils, X).
> live(X):- ask(live, X).
> bill(X) :- ask(bill, X).
> wings(X):- ask(wings, X).
> neck(X):- ask(neck, X).
> size(X) :- ask(size,X).
> color(X):- ask(color, X).
> feet(X):- ask(feet, X).
> flight(X):- ask(flight,X).
> voice(X):- ask(voice,X).
>
>
> ask(A, V):- known(yes, A, V), !.
> ask(A, V):- known(_, A, V),!,fail.
> ask(A, V):- write(A:V), write('? : '),read(Y),asserta(known(Y, A,  
> V)),  Y ==
> yes.


Add to your program the directive:

:- dynamic(known/3).

Cheers,

Paulo


-----------------------------------------------------------------
Paulo Jorge Lopes de Moura, PhD
Assistant Professor
Dep. of Computer Science, University of Beira Interior
6201-001 Covilhã, Portugal

Office 3.18  Ext. 3276
Phone: [phone] Fax: [phone]
Email: <mailto:[e-mail]>

Home page: <http://www.di.ubi.pt/~pmoura>
Research:  <http://logtalk.org/> Blog: <http://blog.logtalk.org/>
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[Paulo Moura]

On 2009/10/19, at 17:30, Sigismo wrote:

> Thanks it works but as ":-dynamic known/3".

It should work both ways, otherwise you would have found a bug. Some  
Prolog compilers, such as SWI-Prolog, declare "dynamic" as an operator  
but that is not required by the ISO Prolog standard.

> Im wondering why it would behave
> like that without the directive?

You're probably calling the known/3 predicate before asserting the  
first clause for it. Calling an unknown predicate is usually an error  
(it depends on the current value of the "unknown" Prolog flag; consult  
the SWI-Prolog documentation).

Cheers,

Paulo


-----------------------------------------------------------------
Paulo Jorge Lopes de Moura, PhD
Assistant Professor
Dep. of Computer Science, University of Beira Interior
6201-001 Covilhã, Portugal

Office 3.18  Ext. 3276
Phone: [phone] Fax: [phone]
Email: <mailto:pmoura@...>

Home page: <http://www.di.ubi.pt/~pmoura>
Research:  <http://logtalk.org/> Blog: <http://blog.logtalk.org/>
-----------------------------------------------------------------

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[Sigismo]

O ok, Thanks again.

Paulo Moura wrote:

On 2009/10/19, at 17:30, Sigismo wrote:

> Thanks it works but as ":-dynamic known/3".

It should work both ways, otherwise you would have found a bug. Some  
Prolog compilers, such as SWI-Prolog, declare "dynamic" as an operator  
but that is not required by the ISO Prolog standard.

> Im wondering why it would behave
> like that without the directive?

You're probably calling the known/3 predicate before asserting the  
first clause for it. Calling an unknown predicate is usually an error  
(it depends on the current value of the "unknown" Prolog flag; consult  
the SWI-Prolog documentation).

Cheers,

Paulo


-----------------------------------------------------------------
Paulo Jorge Lopes de Moura, PhD
Assistant Professor
Dep. of Computer Science, University of Beira Interior
6201-001 Covilhã, Portugal

Office 3.18  Ext. 3276
Phone: [phone] Fax: [phone]
Email: <mailto:[e-mail]>

Home page: <http://www.di.ubi.pt/~pmoura>
Research:  <http://logtalk.org/> Blog: <http://blog.logtalk.org/>
-----------------------------------------------------------------

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[Sigismo]

ok. now im lost again. I tried compiling native in the appendix.http://www.amzi.com/ExpertSystemsInProlog/xsipfrtop.htm . I inserted the dynamic directive similar to the other one right below the op directive hoping that it would fix the problem and I get the following error using the same compiler as before:

5 ?- consult('native.pl').
ERROR: c:/users/sigi/documents/prolog/native.pl:48:0: Syntax error: Operator expected
Warning: c:/users/sigi/documents/prolog/native.pl:107:
        Singleton variables: [X]
Warning: c:/users/sigi/documents/prolog/native.pl:149:
        Singleton variables: [N]
% native.pl compiled 0.02 sec, 0 bytes
true.

6 ?- main.
This is the native Prolog shell.
Type help. load. solve. how(Goal). whynot(Goal). or quit.
at the prompt.
> load.
Enter file name in single quotes (ex. 'birds.nkb'.): 'birds.pl'.
% birds.pl compiled 0.00 sec, 0 bytes
> solve.
ERROR: ask/3: Undefined procedure: known/3
   Exception: (22) ask(nostrils, external_tubular, [ask(nostrils, external_tubular), nostrils(external_tubular), order(tubenose), family(albatross), bird(laysan_albatross), top_goal(laysan_albatross)]) ?
ERROR: ask/3: Undefined procedure: known/3
creep
   Exception: (21) prov(ask(nostrils, external_tubular), [ask(nostrils, external_tubular), nostrils(external_tubular), order(tubenose), family(albatross), bird(laysan_albatross), top_goal(laysan_albatross)]) ? creep
   Exception: (18) prove((nostrils(external_tubular), live(at_sea), bill(hooked)), [order(tubenose), family(albatross), bird(laysan_albatross), top_goal(laysan_albatross)]) ? creep
   Exception: (16) prove((order(tubenose), size(large), wings(long_narrow)), [family(albatross), bird(laysan_albatross), top_goal(laysan_albatross)]) ? creep
   Exception: (14) prove((family(albatross), color(white)), [bird(laysan_albatross), top_goal(laysan_albatross)]) ? creep
   Exception: (9) solve ? creep
   Exception: (8) do(solve) ? creep

[Bill McEnaney]

Sigismo, Please show us your program or part of it.  Maybe we can figure
out what's wrong if we see in context the lines you're computer is
criticizing.  Thanks.

Bill
>
> ok. now im lost again. I tried compiling
> http://www.amzi.com/ExpertSystemsInProlog/xsipfrtop.htm
> http://www.amzi.com/ExpertSystemsInProlog/xsipfrtop.htm . I inserted the
> dynamic directive similar to the other one right below the op
directive and
> I get the following error using the same compiler as before:
>
> 5 ?- consult('native.pl').
> ERROR: c:/users/sigi/documents/prolog/native.pl:48:0: Syntax error:
Operator

> expected
> Warning: c:/users/sigi/documents/prolog/native.pl:107:
>         Singleton variables: [X]
> Warning: c:/users/sigi/documents/prolog/native.pl:149:
>         Singleton variables: [N]
> % native.pl compiled 0.02 sec, 0 bytes
> true.
>
> 6 ?- main.
> This is the native Prolog shell.
> Type help. load. solve. how(Goal). whynot(Goal). or quit.
> at the prompt.
> > load.
> Enter file name in single quotes (ex. 'birds.nkb'.): 'birds.pl'.
> % birds.pl compiled 0.00 sec, 0 bytes
> > solve.
> ERROR: ask/3: Undefined procedure: known/3
>    Exception: (22) ask(nostrils, external_tubular, [ask(nostrils,
> external_tubular), nostrils(external_tubular), order(tubenose),
> family(albatross), bird(laysan_albatross), top_goal(laysan_albatross)]) ?
> ERROR: ask/3: Undefined procedure: known/3
> creep
>    Exception: (21) prov(ask(nostrils, external_tubular), [ask(nostrils,
> external_tubular), nostrils(external_tubular), order(tubenose),
> family(albatross), bird(laysan_albatross), top_goal(laysan_albatross)]) ?
> creep
>    Exception: (18) prove((nostrils(external_tubular), live(at_sea),
> bill(hooked)), [order(tubenose), family(albatross),

bird(laysan_albatross),
> top_goal(laysan_albatross)]) ? creep
>    Exception: (16) prove((order(tubenose), size(large),
wings(long_narrow)),
> [family(albatross), bird(laysan_albatross), top_goal(laysan_albatross)]) ?
> creep
>    Exception: (14) prove((family(albatross), color(white)),
> [bird(laysan_albatross), top_goal(laysan_albatross)]) ? creep
>    Exception: (9) solve ? creep
>    Exception: (8) do(solve) ? creep
> --
> View this message in context:
http://www.nabble.com/Undefined-Procedure-Help-tp25951455p25966388.html
> Sent from the SWI Prolog mailing list archive at Nabble.com.
>
> _______________________________________________
> SWI-Prolog mailing list
> SWI-Prolog@...
> https://mailbox.iai.uni-bonn.de/mailman/listinfo.cgi/swi-prolog
>
>

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[Sigismo]

Hey, here are the two files. I renamed the extension just incase it gets blocked or something like what hotmail does. Thanks in advance.

sigismo
birds.txt
native.txt

Bill McEnaney wrote:

Sigismo, Please show us your program or part of it.  Maybe we can figure
out what's wrong if we see in context the lines you're computer is
criticizing.  Thanks.

Bill
>
> ok. now im lost again. I tried compiling
> http://www.amzi.com/ExpertSystemsInProlog/xsipfrtop.htm
> http://www.amzi.com/ExpertSystemsInProlog/xsipfrtop.htm . I inserted the
> dynamic directive similar to the other one right below the op
directive and
> I get the following error using the same compiler as before:
>
> 5 ?- consult('native.pl').
> ERROR: c:/users/sigi/documents/prolog/native.pl:48:0: Syntax error:
Operator
> expected
> Warning: c:/users/sigi/documents/prolog/native.pl:107:
>         Singleton variables: [X]
> Warning: c:/users/sigi/documents/prolog/native.pl:149:
>         Singleton variables: [N]
> % native.pl compiled 0.02 sec, 0 bytes
> true.
>
> 6 ?- main.
> This is the native Prolog shell.
> Type help. load. solve. how(Goal). whynot(Goal). or quit.
> at the prompt.
> > load.
> Enter file name in single quotes (ex. 'birds.nkb'.): 'birds.pl'.
> % birds.pl compiled 0.00 sec, 0 bytes
> > solve.
> ERROR: ask/3: Undefined procedure: known/3
>    Exception: (22) ask(nostrils, external_tubular, [ask(nostrils,
> external_tubular), nostrils(external_tubular), order(tubenose),
> family(albatross), bird(laysan_albatross), top_goal(laysan_albatross)]) ?
> ERROR: ask/3: Undefined procedure: known/3
> creep
>    Exception: (21) prov(ask(nostrils, external_tubular), [ask(nostrils,
> external_tubular), nostrils(external_tubular), order(tubenose),
> family(albatross), bird(laysan_albatross), top_goal(laysan_albatross)]) ?
> creep
>    Exception: (18) prove((nostrils(external_tubular), live(at_sea),
> bill(hooked)), [order(tubenose), family(albatross),
bird(laysan_albatross),
> top_goal(laysan_albatross)]) ? creep
>    Exception: (16) prove((order(tubenose), size(large),
wings(long_narrow)),
> [family(albatross), bird(laysan_albatross), top_goal(laysan_albatross)]) ?
> creep
>    Exception: (14) prove((family(albatross), color(white)),
> [bird(laysan_albatross), top_goal(laysan_albatross)]) ? creep
>    Exception: (9) solve ? creep
>    Exception: (8) do(solve) ? creep
> --
> View this message in context:
http://www.nabble.com/Undefined-Procedure-Help-tp25951455p25966388.html
> Sent from the SWI Prolog mailing list archive at Nabble.com.
>
> _______________________________________________
> SWI-Prolog mailing list
> [e-mail]
> https://mailbox.iai.uni-bonn.de/mailman/listinfo.cgi/swi-prolog
>
>

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[Nicolas Pelletier-3]

Hello,

On Tue, Oct 20, 2009 at 10:00 PM, Sigismo <ziggydotcom@...> wrote:
>
> http://www.nabble.com/file/p25974653/birds.txt birds.txt
> http://www.nabble.com/file/p25974653/native.txt native.txt

Your problem comes from your use of abolish/2 to retract all clauses
for known/3. In SWI, abolish/2 is meant for static predicates. Modify
your solve/1 predicate to read:

> solve :-
>         retractall(known(_, _, _)),
>         prove(top_goal(X),[]),
>         write('The answer is '),write(X),nl.
> solve :-
>        write('No answer found.'),nl.

You should also pay attention to the errors and warnings you get. When
loading this code under SWI, I get the following error:

> ERROR: /home/nicolas/Desktop/native.pl:48:0: Syntax error: Operator expected

The offending line is:

> ask(Attribute,_,_) :- not multivalued(Attribute),known(yes,Attribute,_),!, fail.

This should be written as:

> ask(Attribute, _, _) :-
>     \+ multivalued(Attribute),
>     known(yes, Attribute, _), !,
>     fail.

I also removed the warnings about singleton variables by prefixing
their names with an underscore. Now, I can solve for the
laysan_albatross, but I did not try any other combination.

HTH,

--
Nicolas
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[Bill McEnaney]

Sigismo,

I know what's making your computer complain about native.txt. On line in
native.txt, you use the word "not" when you need to use "\+" instead.  

You know, I'm sure, that a singleton variable is a variable that appears
only once in a clause.  So maybe you could replace each singleton
variable with the anonymous variable?

Cheers,
Bill

>
> Hey, here are the two files. I renamed the extension just incase it gets
> blocked or something like what hotmail does. Thanks in advance.
>
> sigismo
> http://www.nabble.com/file/p25974653/birds.txt birds.txt
> http://www.nabble.com/file/p25974653/native.txt native.txt
>
> Bill McEnaney wrote:
> >
> >
> > Sigismo, Please show us your program or part of it.  Maybe we can figure
> > out what's wrong if we see in context the lines you're computer is
> > criticizing.  Thanks.
> >
> > Bill
> >>
> >> ok. now im lost again. I tried compiling
> >> http://www.amzi.com/ExpertSystemsInProlog/xsipfrtop.htm
> >> http://www.amzi.com/ExpertSystemsInProlog/xsipfrtop.htm . I

inserted the

> >> dynamic directive similar to the other one right below the op
> > directive and
> >> I get the following error using the same compiler as before:
> >>
> >> 5 ?- consult('native.pl').
> >> ERROR: c:/users/sigi/documents/prolog/native.pl:48:0: Syntax error:
> > Operator
> >> expected
> >> Warning: c:/users/sigi/documents/prolog/native.pl:107:
> >>         Singleton variables: [X]
> >> Warning: c:/users/sigi/documents/prolog/native.pl:149:
> >>         Singleton variables: [N]
> >> % native.pl compiled 0.02 sec, 0 bytes
> >> true.
> >>
> >> 6 ?- main.
> >> This is the native Prolog shell.
> >> Type help. load. solve. how(Goal). whynot(Goal). or quit.
> >> at the prompt.
> >> > load.
> >> Enter file name in single quotes (ex. 'birds.nkb'.): 'birds.pl'.
> >> % birds.pl compiled 0.00 sec, 0 bytes
> >> > solve.
> >> ERROR: ask/3: Undefined procedure: known/3
> >>    Exception: (22) ask(nostrils, external_tubular, [ask(nostrils,
> >> external_tubular), nostrils(external_tubular), order(tubenose),
> >> family(albatross), bird(laysan_albatross),

top_goal(laysan_albatross)]) ?
> >> ERROR: ask/3: Undefined procedure: known/3
> >> creep
> >>    Exception: (21) prov(ask(nostrils, external_tubular), [ask(nostrils,
> >> external_tubular), nostrils(external_tubular), order(tubenose),
> >> family(albatross), bird(laysan_albatross),
top_goal(laysan_albatross)]) ?
> >> creep
> >>    Exception: (18) prove((nostrils(external_tubular), live(at_sea),
> >> bill(hooked)), [order(tubenose), family(albatross),
> > bird(laysan_albatross),
> >> top_goal(laysan_albatross)]) ? creep
> >>    Exception: (16) prove((order(tubenose), size(large),
> > wings(long_narrow)),
> >> [family(albatross), bird(laysan_albatross),
top_goal(laysan_albatross)])

> >> ?
> >> creep
> >>    Exception: (14) prove((family(albatross), color(white)),
> >> [bird(laysan_albatross), top_goal(laysan_albatross)]) ? creep
> >>    Exception: (9) solve ? creep
> >>    Exception: (8) do(solve) ? creep
> >> --
> >> View this message in context:
> > http://www.nabble.com/Undefined-Procedure-Help-tp25951455p25966388.html
> >> Sent from the SWI Prolog mailing list archive at Nabble.com.
> >>
> >> _______________________________________________
> >> SWI-Prolog mailing list
> >> SWI-Prolog@...
> >> https://mailbox.iai.uni-bonn.de/mailman/listinfo.cgi/swi-prolog
> >>
> >>
> >
> > ________________________________________________________________
> > Please visit a saintly hero:
> > http://www.jakemoore.org
> > _______________________________________________
> > SWI-Prolog mailing list
> > SWI-Prolog@...
> > https://mailbox.iai.uni-bonn.de/mailman/listinfo.cgi/swi-prolog
> >
> >
>
> --
> View this message in context:

http://www.nabble.com/Undefined-Procedure-Help-tp25951455p25974653.html
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>
> _______________________________________________
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> SWI-Prolog@...
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>
>

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[Sigismo]

Thanks for all the help. The program compiles without errors and warnings but there is another problem :(.
nostrils:external_tubular? (yes or no) > no.
ERROR: Out of global stack
   Exception: (18) prove((nostrils(external_tubular), live(at_sea), bill(hooked)), [order(tubenose), family(albatross), bird(laysan_albatross), top_goal(laysan_albatross)]) ? creep
   Exception: (16) prove((order(tubenose), size(large), wings(long_narrow)), [family(albatross), bird(laysan_albatross), top_goal(laysan_albatross)]) ? creep
   Exception: (14) prove((family(albatross), color(white)), [bird(laysan_albatross), top_goal(laysan_albatross)]) ? creep
   Exception: (9) solve ? creep
   Exception: (8) do(solve) ? creep
After i got this i did some reasearch and found out that u can use the manpce/0 predicate to adjust stack sizes. I unchecked the limit and ran manpce again it had a value of 1024mb in the text box i currently have for 4gigs or ddr2 ram. I ran it again this time it took a minute after responding negatively to the 1st question or any other question it later gave me the same error. I noticed that the process (plwin.exe) topped out about 1.5gigs of ram. I rewrote the knowlege base to support only two birds and i still recieve the global out of stack error. The updated files are here:
native.pl
birds.pl
Any assistance will be very much appreciated. Thanks in advance Sigismo.

Nicolas Pelletier-3 wrote:

Hello,

On Tue, Oct 20, 2009 at 10:00 PM, Sigismo <[e-mail]> wrote:
>
> http://www.nabble.com/file/p25974653/birds.txt birds.txt
> http://www.nabble.com/file/p25974653/native.txt native.txt

Your problem comes from your use of abolish/2 to retract all clauses
for known/3. In SWI, abolish/2 is meant for static predicates. Modify
your solve/1 predicate to read:

> solve :-
>         retractall(known(_, _, _)),
>         prove(top_goal(X),[]),
>         write('The answer is '),write(X),nl.
> solve :-
>        write('No answer found.'),nl.

You should also pay attention to the errors and warnings you get. When
loading this code under SWI, I get the following error:

> ERROR: /home/nicolas/Desktop/native.pl:48:0: Syntax error: Operator expected

The offending line is:

> ask(Attribute,_,_) :- not multivalued(Attribute),known(yes,Attribute,_),!, fail.

This should be written as:

> ask(Attribute, _, _) :-
>     \+ multivalued(Attribute),
>     known(yes, Attribute, _), !,
>     fail.

I also removed the warnings about singleton variables by prefixing
their names with an underscore. Now, I can solve for the
laysan_albatross, but I did not try any other combination.

HTH,

--
Nicolas
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[Nicolas Pelletier-2]

Hello,

On Fri, Oct 23, 2009 at 13:21, Sigismo <ziggydotcom@...> wrote:
>
> Thanks for all the help. The program compiles without errors and warnings but
> there is another problem :(.
> nostrils:external_tubular? (yes or no) > no.
> ERROR: Out of global stack

Since your knowledge base is small, such an error should prompt you to
look for an infinite loop somewhere in your code. Tracing through it
will show you exactly where things get bad. In short:

?- consult('native.pl').
% native.pl compiled 0.01 sec, 19,648 bytes
true.

?- consult('birds.pl').
% birds.pl compiled 0.00 sec, 24,008 bytes
true.

?- trace, solve.
   Call: (8) solve ? creep
[... skip over lines...]

   Exit: (22) get_user(no, [ask(nostrils, external_tubular),
nostrils(external_tubular), order(tubenose), family(albatross),
bird(laysan_albatross), top_goal(laysan_albatross)]) ? creep
^  Call: (22) asserta(known(no, nostrils, external_tubular)) ? creep
^  Exit: (22) asserta(known(no, nostrils, external_tubular)) ? creep
   Call: (22) no=yes ? creep
   Fail: (22) no=yes ? creep
   Fail: (21) ask(nostrils, external_tubular, [ask(nostrils,
external_tubular), nostrils(external_tubular), order(tubenose),
family(albatross), bird(laysan_albatross),
top_goal(laysan_albatross)]) ? creep
   Redo: (20) prov(ask(nostrils, external_tubular), [ask(nostrils,
external_tubular), nostrils(external_tubular), order(tubenose),
family(albatross), bird(laysan_albatross),
top_goal(laysan_albatross)]) ? creep
^  Call: (21) clause(ask(nostrils, external_tubular), _L396) ? creep
^  Exit: (21) clause(ask(nostrils, external_tubular), (known(yes,
nostrils, external_tubular), !)) ? creep
   Call: (21) prove((known(yes, nostrils, external_tubular), !),
[ask(nostrils, external_tubular), nostrils(external_tubular),
order(tubenose), family(albatross), bird(laysan_albatross),
top_goal(laysan_albatross)]) ? creep

When you hit the Redo, you enter an infinite loop. When the user
answers no, it does not constitute a wrong answer, but a failure to
prove the current goal... So ask/2 should not fail on a 'no' (whatever
the user tells is *true*, even if he/she says 'no'), and prove should
not retry in this case.

Hope this helps,

--
Nicolas
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