On Thu, Nov 11, 2010 at 3:30 PM, Stephen Tetley
The conclusion notes in passing that OCaml's persistence isn't referentially transparent. If the Haskell version wasn't, I'd expect a mea culpa from the authors at this point.
From a quick glance at the paper, the Haskell version is referentially transparent in the standard, trivial sense: the persistence operations all return IO actions. This is of course perfectly fine. What started this thread, however, was the idea of a serialization function producing something like a pure ByteString, and why that, as opposed to (IO ByteString), would be extremely problematic.
What it boils down to is just that any pure "serialization" function would necessarily do nothing useful. Serializing closures from IO actions, on the other hand, I think is a great idea, though probably difficult to implement! - C.