Using monads

Finally, let's take a look at an algebraic structure that helps us build and compose a sequence of computations: a monad. There are countless tutorials and articles on the web that explain monads and how they can be used. In this section, we will look at monads in our own unique and Clojure-y way.

In category theory, a monad is a morphism between functors. This means that a monad transforms the context of a contained value into another context. In pure functional programming languages, monads are data structures used to represent computations that are defined in steps. Each step is represented by an operation on a monad, and several of these steps can be chained together. Essentially, a monad is a composable abstraction of a step of any computation. A distinct feature of monads is that they allow us to model impure side effects, which may be performed in the various steps of a given computation, using pure functions.

Monads abstract the way a function binds values to arguments...