public ParseTreeNode excludeSet() throws SyntaxError {
		ParseTreeNode node = new ParseTreeNode("<exclude-set>");
		if (accept('^')) {
			node.addChild("^");
			node.addChild(charSet());
			if (accept(']')) {
				node.addChild("[");
			}
			if (accept('I')) {
				node.addChild("I");
			}
			if (accept('N')) {
				node.addChild("N");
			}
			node.addChild(excludeSetTail());
			return node;
		} else {
			throw new SyntaxError("Invalid exclude-set");
		}
	}