At least half the value of "IO" is that it marks pure functions as being pure. If Haskell had a "Pure" typeclass instead of IO it would be much the same (except

At least half the value of "IO" is that it marks pure functions as being pure. If Haskell had a "Pure" typeclass instead of IO it would be much the same (except with the wrong default, and you'd have to type more!). I like Purescript, and it might be worth making IO more granular as described. But my opinion is this would be focusing a lot of effort on the less valuable half of IO.