[Haskell-cafe] Why no IO transformer monad?

[Keean Schupke]

Udo Stenzel wrote:

>Keean Schupke <k.schupke at imperial.ac.uk> schrieb am 20.12.04 14:20:54:
>  
>
>>Perhaps you would care to explain this then?
>>    
>>
>
>Damn, I read a pair parens in there where there was none.  The result still
>stands as is: no transformer version of IO is possible.
>  
>
But is that beacuse it really isn't (theoretically) possible, or just 
not possible
to write in Haskell (because it would involve new primitives)?

Surely if IO is (ST RealWorld a) then (StateT RealWorld m a) is more or 
less the
right thing?

    Keean.