class Select extends Iterator {
	Iterator child;
	Predicate pred;

	Select (Iterator child, Predicate pred) {
		this.child = child;
		this.pred = pred;
	} 

	Tuple next() {
		Tuple t;
		while ((t = child.next()) != null ) {
			if (pred(t)) {
				return t;
			}
		}
		return null;
	}

	void open() {
		child.open();
	}
	
	void close() {	
		child.close();
	}
}