User blog comment:Wythagoras/Dollar Function: new version/@comment-1605058-20131023174355/@comment-10429372-20131024054157

If we have a bracket with &&...&& (n &'s), it must be in an arrow of a bracket with &&...& (n-1 &'s). If there isn't such bracket, you have to add it when you want to solve the &&...&& bracket.