public function dump() {
		$prev = null;
		$s = '';
		for ( $node = $this->head; $node; $prev = $node, $node = $node->nextAFE ) {
			if ( $node instanceof Marker ) {
				$s .= "MARKER\n";
				continue;
			}
			$s .= $node->getDebugTag();
			if ( $node->nextNoah ) {
				$s .= " (noah sibling: " . $node->nextNoah->getDebugTag() .
					')';
			}
			if ( $node->nextAFE && $node->nextAFE->prevAFE !== $node ) {
				$s .= " (reverse link is wrong!)";
			}
			$s .= "\n";
		}
		if ( $prev !== $this->tail ) {
			$s .= "(tail pointer is wrong!)\n";
		}
		return $s;
	}