Monads

Monads are tools that help you compose functions.

Like primitive types, monads are structures that can be used as the containers that functors "reach into". The functors grab the data, do something to it, put it into a new monad, and return it.

There are three monads we'll focus on:

So in addition to arrays (map) and functions (compose), we'll have five functors (map, compose, maybe, promise and lens). These are just some of the many other functors and monads that are out there.