# functor

- Understanding contravariance
- Functortown: A Map of the Territory
- Functortown, lesson 8: Mapping a Maybe function
- Functortown, lesson 9: You got monoids in my functors!
- Functortown, lesson 10: Sequencing effects
- “A monad is a monoid in the category of endofunctors”
- Mapping in Python and Haskell