Re: [Info-gnuprologjava] problems running a simple quicksort example

[Daniel Thomas]

Hello,
I have tried running your code on my machine and the results were as
follows:

address@hidden:~$ vim Test.java #I removed the line numbers and edited the path 
to quicksort.pl
address@hidden:~$ vim quicksort.pl
address@hidden:~$ javac -cp 
'/home/daniel/dev/gnuprolog/releases/0.2.5/gnuprologjava-0.2.5/gnuprologjava-0.2.5.jar'
 Test.java
address@hidden:~$ java -cp 
'/home/daniel/dev/gnuprolog/releases/0.2.5/gnuprologjava-0.2.5/gnuprologjava-0.2.5.jar:.'
 Test
ergebnis
0
.(5,8,1,7,3)


What exception do you get? I think that ".(5,8,1,7,3)" is probably the
wrong answer as it doesn't appear to be particularly sorted.

There is one bug I have found in your prolog:
teilen(Element, [Kopf|Rset], Kleiner, [Kopf|Groesser]):-teilen(Element,
        Rest, Kleiner, Groesser).
"[Kopf|Rset]" should probably be "[Kopf|Rest]"

That doesn't fix the missorting though.

Does this help you? There is a demo program in the demo directory of the
release zip file.

In 0.3.0 the return codes of Interpreter.execute(Goal) etc. will be
changed to be an enum which will make System.out.println(rc); print
something slightly more useful than 0;


Daniel

On Wed, 2010-11-10 at 14:51 +0100, Benjamin Martin Brunzel wrote:
> Hi Folks,
> 
> I am currently trying to run a simple quicksort example using gnu prolog
> for java. I get an exception every time I  use a prolog file with more
> then one rule in it.
> I think the problem might be the representation of lists in a CompoundTerm
> object.
> Does anyone know what is wrong with it?
> Is there a simple example program available?
> 
> The Java Class:
> 
>   1 import gnu.prolog.term.*;
>   2 import gnu.prolog.vm.Environment;
>   3 import gnu.prolog.vm.Interpreter;
>   4 import gnu.prolog.vm.PrologException;
>   5
>   6
>   7 public class Test {
>   8
>   9         /**
>  10          * @param args
>  11          * @throws PrologException
>  12          */
>  13         public static void main(String[] args) throws PrologException {
>  14
>  15                 Environment e = new Environment();
>  16                
> e.ensureLoaded(AtomTerm.get("C:\\Path\\to\\prolog\\files\\quicksort.pl"));
>  17                 Interpreter i = e.createInterpreter();
>  18                 e.runInitialization(i);
>  19
>  20                 VariableTerm ergebnis = new VariableTerm("ergebnis");
>  21                 IntegerTerm[] elemente = new IntegerTerm[5];
>  22                 elemente[0] = new IntegerTerm(5);
>  23                 elemente[1] = new IntegerTerm(8);
>  24                 elemente[2] = new IntegerTerm(1);
>  25                 elemente[3] = new IntegerTerm(7);
>  26                 elemente[4] = new IntegerTerm(3);
>  27
>  28                 CompoundTerm liste = new CompoundTerm(".", elemente);
>  29
>  30                 Term[] argumente = {ergebnis, liste};
>  31
>  32                 CompoundTerm anfrage = new CompoundTerm("quicksort",
> argumente);
>  33
>  34                 System.out.println(ergebnis);
>  35
>  36                 Interpreter.Goal goal = i.prepareGoal(anfrage);
>  37                 int rc = i.execute(goal);
>  38                 System.out.println(rc);
>  39
>  40                 System.out.println(ergebnis);
>  41
>  42         }
>  43
>  44 }
> 
> The Prolog File:
> 
> quicksort(A, A).
> quicksort([Kopf|Rest], SortierteListe):- teilen(Kopf, Rest, Kleiner,
> Groesser),quicksort(Kleiner, Kleiner_Sortiert),quicksort(Groesser,
> Groesser_Sortiert),append(Kleiner_Sortiert    , [Kopf|Groesser_Sortiert],
> SortierteListe).
> teilen(_, [], [], []).
> teilen(Element, [Kopf|Rest], [Kopf|Kleiner], Groesser):-Kopf < Element,
> !,teilen(Element, Rest, Kleiner, Groesser).
> teilen(Element, [Kopf|Rset], Kleiner, [Kopf|Groesser]):-teilen(Element,
> Rest, Kleiner, Groesser).
> 
> 
> I used the version 0.2.5
> 
> Please note that I am not on the mailing list so please cc me on your
> answers.
> 
> Thanks for your support.
> 
> 
>

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