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 Chapter 16 Outline
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* 16.1 Functor
* 16.2 What's a functor?
* 16.3 There's a whole lot of fmap goin' round
* 16.4 Let's talk about f baby

  * 16.4.1 Shining star come into view
  * 16.4.2 Exercises: Be Kind

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  * 16.4.3 A shining star for you to see
  * 16.4.4 Functor is function application
  * 16.4.5 A shining star for you to see what your f can truly be
  * 16.4.6 Type classes and constructor classes

* 16.5 Functor Laws

  * 16.5.1 Identity
  * 16.5.2 Composition
  * 16.5.3 Structure preservation

* 16.6 The Good, the Bad, and the Ugly

  * 16.6.1 Composition should just work

* 16.7 Commonly used functors

  * 16.7.1 The functors are stacked and that's a fact
  * 16.7.2 What if we lift twice?
  * 16.7.3 Wait, how does that even typecheck?
  * 16.7.4 Lift me baby one more time
  * 16.7.5 The real type of thing going down
  * 16.7.6 Get on up and get down
  * 16.7.7 One more round for the P-Funkshun
  * 16.7.8 Stay on the scene like an fmap machine
  * 16.7.9 Exercises: Heavy Lifting

* 16.8 Transforming the unapplied type argument
* 16.9 QuickCheck Functor instances
* 16.10 Exercises: Instances of Func

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* 16.11 Ignoring possibilities

  * 16.11.1 Maybe
  * 16.11.2 Exercise: Possibility
  * 16.11.3 Either
  * 16.11.4 Short Exercise

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* 16.12 A somewhat surprising functor
* 16.13 More structure, more functors
* 16.14 IO Functor
* 16.15 What if we want to do something different?
* 16.16 Functor are unique to a datatype
* 16.17 Chapter exercises

  These exercises do not have titles, like previous chapters, but they do have
  subordinate elements, so I'm listing the problem description here, instead.

  * 16.17.1 Determine if a valid Functor can be written for the datatype
    provided

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  * 16.17.2 Rearrange the arguments to the type constructor of the datatype so
    the functor instances works.

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  * 16.17.3 Write Functor instances for the following datatype

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* 16.18 Definitions

  * Higher-kinded polymorphism
  * Functor
  * Lifting
  * George Clinton (the musician)

* 16.19 Follow-up resources

  * Haskell Wikibook; The Functor Class
  * Mark P. Jones; A system of constructor classes: overloading and implicit
    higher-order polymorphism
  * Gabriel Gonzalez; The functor design pattern