Problems with notations of a varying length

We consider the problems posed by notations which have a varying length. The constructor for the mathematical object may have an arbitrary size, within certain constraints. This may mean that it is impossible to define a notation for these objects in the framework developed earlier. In order to deal with this problem we suggest the use of some iterator element. If these are used in conjunction with accessor template functions one may circumvent this problem easily.

How to deal with notations of 
no fixed length