\section{Comparison with other notebook systems}

Cadabra is not built on IPython or Sage notebook. There are various
reasons for this, but the most important one is probably that I am not
a strong believer in the idea that ``the Mathematica and Maple
notebook interfaces are the ideal to strive for''. In fact, I think
there are many things wrong with these interfaces, not

By tacking on to IPython on Sage, I would not be free to experiment
with different basic structure. 

Simple shortcomings: Most notebook systems lack a multiple view facility.
Many lack an unlimited undo/redo stack, which tracks complete changes
to the document, not just within a single cell.

Structural shortcomings: 
