src/builtin/PRED_$begin_exception_1.java

package com.googlecode.prolog_cafe.builtin;
import com.googlecode.prolog_cafe.exceptions.JavaException;
import com.googlecode.prolog_cafe.exceptions.PrologException;
import com.googlecode.prolog_cafe.lang.BlockPredicate;
import com.googlecode.prolog_cafe.lang.JavaObjectTerm;
import com.googlecode.prolog_cafe.lang.Operation;
import com.googlecode.prolog_cafe.lang.OutOfLoop;
import com.googlecode.prolog_cafe.lang.Prolog;
import com.googlecode.prolog_cafe.lang.PrologControl;
import com.googlecode.prolog_cafe.lang.Term;
/**
 * <code>'$begin_exception'/1</code><br>
 * @author Mutsunori Banbara (banbara@kobe-u.ac.jp)
 * @author Naoyuki Tamura (tamura@kobe-u.ac.jp)
 * @version 1.2
 */
class PRED_$begin_exception_1 extends BlockPredicate {
    Term arg1;

    public PRED_$begin_exception_1(Term a1, Operation cont) {
	arg1 = a1;
	this.cont = cont;
    }

    @Override
    public Operation exec(Prolog engine) {
        engine.setB0();
	Term a1;
	a1 = arg1;

	if (! a1.unify(new JavaObjectTerm(this), engine.trail))
	    return engine.fail();
	PrologControl ctl = engine.control;
	Operation code = cont;
	int B = engine.stack.top();
	this.outOfScope = false;
	this.outOfLoop  = false;
	engine.trail.push(new OutOfLoop(this));

	try {
	  do {
	    if (ctl.isEngineStopped()) break;
	    if (outOfLoop) break;
	    code = code.exec(engine);
	  } while (engine.halt == 0);
	} catch (PrologException e) {
	    if (outOfScope)
		throw e;
	    engine.setException(engine.copy(e.getMessageTerm()));
	    engine.cut(B);
	    return engine.fail();
	} catch (Exception e) {
	    if (outOfScope)
		throw new JavaException(e);
	    engine.setException(new JavaObjectTerm(e));
	    engine.cut(B);
	    return engine.fail();
	}
	return code;
    }
}