Functional Setters

Exercises

1. As we saw with free map on Array, define free map on Optional and use it to compose setters that traverse into an optional field.

2. Take a struct, e.g.:

   struct User {
     let name: String
   }
   

   Write a setter for its property. Take (or add) another property, and add a setter for it. What are some potential issues with building these setters?

3. Take a struct with a nested struct, e.g.:

   struct Location {
     let name: String
   }
   
   struct User {
     let location: Location
   }
   

   Write a setter for userLocationName. Now write setters for userLocation and locationName. How do these setters compose?

4. Do first and second work with tuples of three or more values? Can we write first, second, third, and nth for tuples of n values?

5. Write a setter for a dictionary that traverses into a key to set a value.

6. Write a setter for a dictionary that traverses into a key to set a value if and only if that value already exists.

7. What is the difference between a function of the form ((A) -> B) -> (C) -> (D) and one of the form (A) -> (B) -> (C) -> D?