Monads

What is a monad?

A monad wraps a value in a similar way to a functor. However, a monad has an additional function, called bind, that:

• Accepts a single parameter
• Returns a value wrapped in a monad

Unlike map, the bind function, itself, is responsible for wrapping the return value. This means that the bind function can decide what sort of monad to wrap the result in.

Here is an example, the function, oneover, returns $\frac{1}{x}$, wrapped in a Just monad: