In functional programming languages, a monad is a pattern where functions wrap their return value in a type that requires additional computation. A common monad is the "maybe" type, way either contain a result or a null value. A series of functions that produce a "maybe" can then be composed together with a "bind" operator. While Javascript promises are not technically monads, they follow a similar pattern.
In Hoon, there are a number of functions that are either monads or follow a similar pattern. Threads are written this way, and the unit type and associate functions are similar to "maybe".
Further reading
- Threads guide: Learn how to write threads.
- stdlib reference section 2a: These functions are for manipulating and composing units.