RE: String representation of an Eclipse Term

Hi Roland, 

I'm glad you asked this question. We deliberately changed the behaviour of
toString() as it was misleading a lot of developers. The trouble is that
java does not know enough about the ECLiPSe term to produce from it a string
which is both human-readable and reliably ECLiPSe-readable. 

The best way to convert a term to a string so that it has these properties
is to use the writeq/2 predicate on the ECLiPSe side, i.e. something like

term2String(YourTerm, YourString):-
  open(string(""), update, StringStream), 
  writeq(StringStream, YourTerm), 
  get_stream_info(StringStream, name, YourString), 
  close(StringStream).

tempest: eclipse -b test.pl
ECLiPSe Constraint Logic Programming System [kernel]
Copyright Imperial College London and ICL
Certain libraries copyright Parc Technologies Ltd
GMP library copyright Free Software Foundation
Version 5.3 #41, Sat Nov 24 13:49 2001
[eclipse 1]:  term2String('_yarg'(snoll, "grotch", 4+5), String).

String = "'_yarg'(snoll, \"grotch\", 4 + 5)"
Yes (0.00s cpu)
[eclipse 2]: 

We considered putting something in the Java interface which would have been
a wrapper for the writeq/2 builtin, but decided against it. 

BTW I think the use of writeq/2 instead of toString() was hinted at in the
release notes page "Changes to the Java-ECLiPSe Interface, v5.2 to v5.3". 

hope this helps.

josh

Developer, Parc Technologies Limited
josh.singer@parc-technologies.com
http://www.parc-technologies.com

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-----Original Message-----
From: RolWenzel@aol.com [mailto:RolWenzel@aol.com]
Sent: Thursday, December 13, 2001 4:27 PM
To: eclipse-users@icparc.ic.ac.uk
Subject: [eclipse-users] String representation of an Eclipse Term


Hi,

I have a problem getting the correct string representation of an Eclipse
Term since I upgraded to the version 5.3 of Eclipse.

In Version 5.2, eclipse_to_java_formatted.readTerm().toString() provided the
correct string representation, for example "foo (X, a).".
In Version 5.3, you will get an object containing the Eclipse-classes, for
instance "class com.parctechnologies.eclipse.CompoundTermImpl" with a
functor, the arity and so on.

Trying to create the "nicer" string out of the Object, I wrote the function
"getString" that you can find at the end of this mail.
It works fine, but it doesn't recognize any variables, because they were
represented as "null" and hence have no "toString" method.
Simply printing "X" for "null" will result in problems, because foo(X, Y)
will be printed as foo(X, X).
Is there another way to translate variables to its original name?
Or better: is there a build in function in the Java Interface to get the
string representation from an Eclipse Term, and I just didn't see it?

Thank you for any hint,
Roland Wenzel

---

 public String getString(Object EclipseTerm)
 {
  String result = "";
  LinkedList LinkList;
  int i;

  if (EclipseTerm == null) {
   return "";
  }

  if (EclipseTerm.getClass().toString().equals("class
com.parctechnologies.eclipse.CompoundTermImpl")) {
   result = ((CompoundTerm)EclipseTerm).functor();
   if (((CompoundTerm)EclipseTerm).arity() >= 1) {
    result = result + "(";
    for (i=1; i <= ((CompoundTerm)EclipseTerm).arity(); i++) {
     result = result + getString(((CompoundTerm)EclipseTerm).arg(i));
     if (i < ((CompoundTerm)EclipseTerm).arity()) {
      result = result + ", ";
     }
    }
    result = result + ")";
   }
  } else if (EclipseTerm.getClass().toString().equals("class
com.parctechnologies.eclipse.Atom")) {
   result = result + ((Atom)EclipseTerm).functor().toString();
  } else if (EclipseTerm.getClass().toString().equals("class
java.util.LinkedList")) {
   result = result + "[";
   LinkList = (LinkedList)EclipseTerm;
   while (!LinkList.isEmpty())
   {
    result = result + getString(LinkList.getFirst());
    LinkList.removeFirst();
    if (!LinkList.isEmpty()) {
     result = result + ", ";
    }
   }
   result = result + "]";
  } else {
   result = result + EclipseTerm.toString();
  }

  return result;
 }