/** Reactivate this choice point to return new results. */
public void pump() {
if (context instanceof Generator) {
((Generator) context).pump(this);
} else {
// The top level iterator is in charge and will restore and run this choice point itself
}
}
/**
* Initialize the choice point state.
*
* @param interpreter the parent interpreter whose state is to be preserved here, its arg stack
* defines the parameters for the target goal
*/
@Override
public void init(LPInterpreter interpreter) {
super.init(interpreter);
context = interpreter.getContext();
generator = interpreter.getEngine().generatorFor(goal);
generator.addConsumer(this);
resultIndex = 0;
}
/**
* Find the next result triple and bind the result vars appropriately.
*
* @param interpreter the calling interpreter whose trail should be used
* @return FAIL if there are no more matches and the generator is closed, SUSPEND if there are no
* more matches but the generator could generate more, SATISFIED if a match has been found.
*/
public synchronized StateFlag nextMatch(LPInterpreter interpreter) {
while (resultIndex < generator.results.size()) {
Triple result = (Triple) generator.results.get(resultIndex++);
// Check if we have finished with this generator
if (resultIndex >= generator.results.size() && generator.isComplete()) {
generator.removeConsumer(this);
}
if (bindResult(result, interpreter)) {
return StateFlag.SATISFIED;
}
}
if (generator.isComplete()) {
setFinished();
generator.removeConsumer(this);
return StateFlag.FAIL;
} else {
return StateFlag.SUSPEND;
}
}
/** Return true if this choice point could usefully be restarted. */
public boolean isReady() {
return generator.numResults() > resultIndex;
}