Where is the data constructor for 'State'?

Question

After reading a couple of tutorials on Haskell state monads I wanted to try them out myself. The tutorials I read claim that the Control.Monad.State provide the following defini

Answer 1

It doesn't exist any more. Unfortunately, this makes many Haskell resources on the web about it outdated.

To create a value, you can just use the state function:

state :: (s -> (a, s)) -> State s a

runState, which used to be a field of State, is now just a normal function itself, but it works in the same way as before.

State has been rewritten in terms of the StateT monad transformer:

type State s = StateT s Identity

StateT itself has a constructor StateT that functions very similarly to the old State constructor:

newtype StateT s m a = StateT { runStateT :: s -> m (a, s) }

The only difference is that there is an extra parameter m. This is just a slot where you can add in any other monad, which StateT then extends with state-handling capabilities. Naturally, to regain the old functionality of State, you just have to set m to Identity, which doesn't do anything.

newtype Identity a = Identity { runIdentity :: a }