[Haskell-cafe] Why no IO transformer monad?

[Ben Rudiak-Gould]

Ross Paterson wrote:

 >But IO is not ST RealWorld (even if GHC pretends it is): other users
 >of the world are not waiting for the new world produced by your Haskell
 >program.

They're *part* of the world. IO = State RealWorld makes sense if you 
think of RealWorld as encapsulating the entire state of the universe, 
including "other users".

The only trouble is that concurrent processes end up containing each 
other. I'm not entirely convinced that this can't be solved with some 
sort of fixed-point trick.

-- Ben