5. In assignment 2, we discovered that version 3-type lists (the ones that
work like Church numerals) made it much easier to define operations
like `map` and `filter`. But now that we have recursion in our toolbox,
5. In assignment 2, we discovered that version 3-type lists (the ones that
work like Church numerals) made it much easier to define operations
like `map` and `filter`. But now that we have recursion in our toolbox,