Tony Morris

I'm not quite sure what that means. IO as it is in Haskell, and as we implemented in Scala, maintains referential transparency of expressions.

Yeah and you can apply equational reasoning as others data types like list but coincidentally (and arbitrarily) ghc and other compiles use it as the main point entry to do ffi, right? Other compilers could use other data types (like Eff in purescript)

Yes they do, since the denotational semantics of IO is "whatever." This is a valid criticism of IO. But IO is as referential transparent as [], Maybe, ((->) t), etc.. If the focus were shifted to the correct properties of IO, we could all work toward something better imo.

Can you elaborate? When I i.e. readFile in haskell, it is IO right? How is that referential transparent? I cannot replace the call with its value the next time, since the file might not exist