It might take some developer discipline to set things up that way initially, but the great thing about Haskell is that once you have it set up, it does not requ

It might take some developer discipline to set things up that way initially, but the great thing about Haskell is that once you have it set up, it does not require any developer discipline. If your system runs in the Foo monad, you can only do operations that have been made available to you. This is the big problem that other languages have...you simply cannot enforce some of these guarantees.