When working with a collection, we can also define the processing recursively. We can, for example, define the map() function recursively. The formalism could be stated as follows:
We've defined the mapping of a function to an empty collection as an empty sequence. We've also specified that applying a function to a collection can be defined recursively with a three step expression. First, apply the function to all of the collection except the last element, creating a sequence object. Then apply the function to the last element. Finally, append the last calculation to the previously built sequence.
