As far as I understand it IO is a special case of a state monad (where
the state is the "World". If this is the case and there is a state-transformer
(StateT) then it should be possible to write an IO transformer. Unfortunately
I also think because of some magic in the ST and IO monads, you cannot write
the transformer yourself, as it would require compiler support.


   Keean.

Henning Sato von Rosen wrote:

Hi all!

For each basic monad there seems to be a corresponding transformer,
e.g.  'StateT' for 'State' and so on.

I guess the reason lies in the fact that if there were an IO
Transformer monad, one might run it and get the 'Universe' out of the
IO monad.

But, I am working on understanding IO magic, on a much more concrete
level, so I am am looking for a really good explanation of the above.
(And the IO monad in general.)

Thanks!

/Henning
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