On Thu, Nov 11, 2010 at 1:57 PM, Stephen Tetley <stephen.tet...@gmail.com> wrote: > On 11 November 2010 18:01, C. McCann <c...@uptoisomorphism.net> wrote: > >> For instance, assuming serialize can be applied to functions of any >> type, it would probably be trivial to write a function (isExpr :: a -> >> Bool) that reports whether an arbitrary term is a primitive value or >> the result of some expression [SNIP] > > Persistent functional languages usually give serialized values > including closures a dynamic type. So can you write isExpr :: Dynamic > -> Bool ?
But it's not the type of the serialized value that's at issue, it's the type of the serializable values. Anything that lets you convert an arbitrary closure into something with internals open to inspection will likely have dire consequences for parametricity and referential transparency. Remember, the problem isn't what you do with the serialized form itself, it's what you can learn via it about the original value it was serialized from. To retain sanity, either "types that can be serialized" must be marked explicitly (perhaps in the context, similar to having a Data.Typeable constraint) to indicate potential non-parametric shenanigans, or the result of serializing and inspecting a value must be quarantined off, such as with IO. Or some other mechanism, but those seem like the obvious choices. Having a full serialization function without some restriction along those lines would be like renaming unsafePerformIO to runIO, moving it to Control.Monad.IO, and telling people "hey, just don't misuse this and everything will be okay". - C. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
