The type of the monad containing values of type 'a

return a makes a monadic container containing the value a.

m >>= f extracts the value a from the monadic container m and returns f a.

f >=> g composition of the two monadic functions f and g.

f >=> g is equivalent to fun a -> f a >>= g.

map f m maps the values in the monadic container m with the function f.

Remove one level of container. join m is equivalent to mm >>= fun m -> m.

f <*> m applies the function contained in f to the content of the monadic container m and injects the result into a new monadic container.