## Comment: Limitations of STL Design (Score 1) 80

The iterator based approach of STL works very elegantly for 1 dimensional data structures but fails to generalize cleanly for higher dimensional structures. For example, there is no easily defined way of iterating over a 2d array or a graph. Also, the notion of regular types, discussed in your book Elements of Programming, also fails to generalize for 2 or higher dimensional types, like complex numbers and matrices. They lack the total ordering property.

Of course, you can artificially define an ordering, say force a row-by-row iteration over a 2D-Array or a breadth-first iterator over a tree or an artificial ordering on complex numbers, but such constructs feel artificial. Do you think this limitation is fundamental to the iterator based design approach?