What should a GUI do; also , why case sensitive?



> The linear string form of a mathematical expression is a terrible
> "model"!!  The model should surely be the tree-structured form which
> logically includes a main operator/symbol, a list of attributes, and a
> list of arguments, each of which is either another tree or a symbol.
It was chosen as an example since it satisfies the following:
- The document mustn't know anything about math, in particular the expression 
is fully simplified in the pre-display sense.
- Input and Output language is the same.
- No formatting (e.g. line-breaking) is done on the output.

Maybe 2. from the list in the post by Richard Fateman
> 2. the formatted version, also in lisp, that  changes stuff like
> a*b^(-1)  into  a/b  for pre-display consideration
is a more reasonable choice.

Michael