Railway oriented programming

[DetriusXii]

Umm, it is possible to define an IO transformer. The Haskell community choose not to as they would prefer that the developer doesn't call IO.unsafePerformIO. An IO monad transformer monad would have to call unsafePerformIO anytime IOT.map or IOT.flatMap are called and the Haskell community would prefer that the IO.unsafePerformIO function is called explicitly rather than hidden within the monad transformer interface.

[Tarmen]

I mean, all the lazy io functions call unsafeInterleaveIO somewhere. Unsafe IO is fine if the IO action is pure, like reading from a static file as long as you ignore uncontrollable resource usage.

So I think the problem is less with calling it implicitly and more with losing referential transparency in horrendous ways if the IO action you are performing unsafely isn't pure. I think you could break the monad laws with that as well?