[Haskell-cafe] foild function for expressions

[Pablo Nogueira]

I believe the exercise is about understanding folds.

There are two references that are related to the exercise:

  A tutorial on the universality and expressiveness of fold, by Graham Hutton.
  Dealing with large bananas, by Ralf Lammel, etc.

The last paper motivates well the need to gather all the function
parameters to the fold (ie, the algebra) in a separate record
structure.

I don't think being told what to write will help you understand what
is going on, which is simpler than it seems.