JACK: JASE example

// Performs depth-first exploration of a search tree

public class SDepthFirstExploration implements SExploration
{
    private ObjectContainer stack = new ObjectContainer();

    private SChoice rootChoice;	// for reset()
    private SMarkedConstraintSystem rootSystem; // for reset
    
    public SDepthFirstExploration(ConstraintSystem system,SChoice choice)
    {       
	rootChoice=choice;
	reset(system);
    }

    // Reset everything
    public void reset(ConstraintSystem system)
    {

	// restore the constraint system and re-initialise the root choice
	rootSystem=system.createMarkedSystem(); 
	rootChoice.reset();

	// Push the root node onto the stack
	stack.removeAll();
	stack.add(new SNode(rootSystem,rootChoice));
    }

    
    // Returns null when finished
    public SNode performOneStep()
    {

	int stackSize=stack.size();

	if (stackSize==0) return null;

	// Pop the current element from the stack

	SNode node=(SNode)(stack.get(stackSize-1));
	stack.remove(stackSize-1);

	// If this is one of the special nodes, return it
	// (it has no children)

	if (node.isSuccess() || node.isFailure())
	    return node;

	// Create the child

	SNode nextNode=node.createNextChild();

	// Push the same node again, if this wasn't the last child
	
	if (node.hasMoreChildren())
	    stack.add(node);

	// Push the child

	stack.add(nextNode);

	return nextNode;
    }

}