Doing assert from java? - Ciao-users

21 Dec 2000


      Hello,
I'm using Ciao-1.7p30 on a Windows NT sp5 machine.
I'm trying to determine how, using the Java interfaces,
to tell the prolog server to do an assert.
I have tried constructing a goal G containing asserta(foo(5))
followed by a call to G.query().  A subsequent call to 
G.nextSolution() will simply hang in a read, and a
G.terminate() call generates a PLException: Termination has not 
been accepted by the server.
(Using a goal doesn't really seem correct to do an assert, but
I see no other class that might be appropriate).
I can successfully run the queens example (using both the
Javasoft JDK and the Microsoft VM) in the library\
javall\Examples\java2pl directory, both as distributed and
integrated into my program -- so I believe my general usage is 
alright.
The relevant section of java code I'm using is appended
to the end of this message (as well as a mod to PLConnection).
Any help is appreciated!
-- Dan
larner(a)parc.xerox.com
--------------------------------------------
PLTerm solution; 
    		
// build up foo(5).
String fooFunctor = "foo";
PLTerm[] fooArgs = new PLTerm[1];
fooArgs[0] = new PLInteger(5);
PLStructure foo = new PLStructure(fooFunctor, fooArgs);
// build up asserta(foo(5)).
String assertaFunctor = "asserta";
PLTerm[] assertaArgs = new PLTerm[1];
assertaArgs[0] = foo;
PLStructure assertFoo = new PLStructure(assertaFunctor, assertaArgs);
// create a goal holding the asserta(foo(5)).
currentGoal = new PLGoal(sm_plServer, assertFoo);
// tell prolog asserta(foo(5)).
System.out.println("Doing " + currentGoal);
currentGoal.query();
// trying currentGoal.terminate(); at this point 
// generates PLException: Termination has not 
// been accepted by the server
// trying solution = currentGoal.nextSolution(); at 
// this point just hangs in a read
--------------------------------------------
I found that when running with the Microsoft
VM, I needed to add a close method to PLConnection, and
call it before exit in order to have the prolog process
terminate. Here's the method for anyone interested:
/** closes the connection - it's no longer usable
   */
 public void close() {
      try { plIn.close(); } 
      catch (Exception e) {
    	  System.err.println("PLConnection: Problem closing plIn " + e);
      }
      try { evIn.close(); } 
      catch (Exception e) {
    	  System.err.println("PLConnection: Problem closing plIn " + e);
      }
      plOut.close();
      evOut.close();
  }