Haskell Language Common monads as free monads Free (Reader x) ~~ Reader (Stream x)
Example
Given
data Reader x a = Reader (x -> a)
we have
data Free (Reader x) a
= Pure a
| Free (x -> Free (Reader x) a)
which is isomorphic to
data Demand x a
= Satisfied a
| Hungry (x -> Demand x a)
or equivalently Stream x -> a with
data Stream x = Stream x (Stream x)
