Re: [Info-gnuprologjava] How to instance a Term with a functor?

[Daniel Thomas]

Hello,

GNU Prolog is a completely separate implementation to GNU Prolog for Java (though confusion is understandable). I take it that your problem is that you want a term (a+b) but get one which is enclosed in single quotes when this is not the behaviour you were expecting.

This is because you are creating an AtomTerm containing 'a+b' rather than a compound term composed of the atoms a and b bound by the infix function +. 
I suspect that you want to use http://www.gnu.org/s/gnuprologjava/api/gnu/prolog/io/TermReader.html#stringToTerm(gnu.prolog.io.ReadOptions, java.lang.String, gnu.prolog.vm.Environment) or http://www.gnu.org/s/gnuprologjava/api/gnu/prolog/io/TermReader.html#stringToTerm(java.lang.String, gnu.prolog.vm.Environment) depending on whether you want to be able to be able to get variables out by name when they are in the string you pass using http://www.gnu.org/s/gnuprologjava/api/gnu/prolog/io/ReadOptions.html#variableNames

I hope that helps,

Daniel

P.S. Sorry for the delay I haven't had much internet recently.

On Sun, 2011-08-07 at 13:57 +0200, Carlos-Manuel LÓPEZ-ENRÍQUEZ wrote:
>     Good morning,
>     
>     I just started using the API gnuprologjava-0.2.6.jar. I have a parser of a language written in prolog and implemented by defining new operators with 'op/3'. Therefore, I take advantage of natural treatment of functors already built in prolog.  This parser works well and I want to use it from a java program. 
>     
>     I made a first exercise for referencing a simple _expression_ (a+b) to a variable term A by using the  '=/2' operator (i.e., A=(a+b) ) in the same way as in the gprolog interface: gprolog.png
>     
>

>     This is a basic requirement for parsing the language expressions. I have coded a simple method parser(String) which constructs the terms and execute a goal. I have tried to use AtomTerm and VariableTerm classes to unify with an _expression_ but I don't get the same result as in gprolog.
>     
>     In the case of the code using AtomTerm:
>     public void parser(String exp){
>     exp = "("+exp.trim()+")"; 
>     AtomTerm t_exp = AtomTerm.get(exp);
>     VariableTerm at_A = new VariableTerm("A");
>     
>     Term[] args =  {at_A,t_exp};
>     CompoundTerm goalTerm = new CompoundTerm("=", args);
>     
>     System.out.println("? "+goalTerm.toString());
>     
>     Goal goal = interpreter.prepareGoal(goalTerm);
>     try {
>     int rc=-1;
>     do{
>     rc=interpreter.execute(goal);
>     System.out.println("! "+at_A.name+" = "+at_A.value);
>     }while(rc==0);
>     
>     } catch (PrologException e1) {
>     e1.printStackTrace();
>     }
>     }
>     
>     
>     I get the output:
>     ? A = '(a+b)'
>     ! A = '(a+b)'
>     … but AtomTerm instances my _expression_ as an atom in quotes.
>     
>     
>     I tried also with VariableTerm class:
>     public void parser(String exp){
>     exp = "("+exp.trim()+")"; 
>     Term t_exp = new VariableTerm(exp);
>     VariableTerm at_A = new VariableTerm("A");
>     
>     Term[] args =  {at_A,t_exp};
>     CompoundTerm goalTerm = new CompoundTerm("=", args);
>     
>     System.out.println("? "+goalTerm.toString());
>     
>     Goal goal = interpreter.prepareGoal(goalTerm);
>     try {
>     int rc=-1;
>     do{
>     rc=interpreter.execute(goal);
>     System.out.println("! "+at_A.name+" = "+at_A.value);
>     }while(rc==0);
>     
>     } catch (PrologException e1) {
>     e1.printStackTrace();
>     }
>     }
>     
>     
>     with the output: 
>     ? A = (a+b)
>     ! A = _A0
>     …but it doesn't works either.
>     
>     
>     Do you know if I can instance some gnu.prolog.term.* with an _expression_ (actually a functor) and how? or maybe you have another alternative? 
>     
>     
>     Best regards and thanks in advance,
>     
>     
>     --
>     Carlos-Manuel
>     ______________________________________________________
>     PhD Student at
>     ______________________________________________________
>     LIG Laboratory - HADAS group
>     681 Bât D-306, Rue de la Passerelle, 38400 Saint Martin d'Hères, France
>     Tel (+33) 4 76 82 72 31, Fax (+33) 4 76 82 72 87 
>     
>     LAFMIA - Universidad de las Américas, Puebla 
>     CENTIA , Ex-hda Sta. Catarina Mártir, 72820 Cholula, Puebla, México 
>     Tel (+52) 222 2 29 26 06, Fax (+52) 222 2 29 21 38
>     ______________________________________________________
>     
>

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