[Haskell-cafe] serialize an unknown type

Corentin Dupont corentin.dupont at gmail.com
Sun Oct 21 20:11:50 CEST 2012

Hi Iustin,
yes I want to deserialize an unknown type based on the content of the file
(in this example).
Let's say I can reduce the spectum of types to: Strings, all the types in
Enum, Ints. Is it possible?

My real problem is that on my web interface I want to use web routes to
allow a user to pass an Event back to the engine.
The problem is that it seems that web-routes only accepts Strings (or some
known types) to be passed on the web route, whereas I need to pass random

On Sun, Oct 21, 2012 at 8:00 PM, Iustin Pop <iusty at k1024.org> wrote:

> On Sun, Oct 21, 2012 at 07:20:10PM +0200, Corentin Dupont wrote:
> > Hi,
> > Sorry if it was not enough explicit.
> > I want to write functions like this:
> >
> > serialize :: (Show a) => Event a -> IO ()
> > deserialize :: (Read a) => IO () -> Event a
> >
> > The functions would write and read the data in a file, storing/retrieving
> > also the type "a" I suppose...
> Can't you simply, when defining the type event, add a "deriving (Show,
> Read)"? Then the standard (but slow) read/show serialisation would work
> for you.
> If you're asking to de-serialise an unknown type (i.e. you don't know
> what type it should restore a-priori, but you want to do that based on
> the contents of the file), things become a little more complex. Unless
> you can further restrict the type 'a', really complex.
> Maybe stating your actual problem, rather than the implementation
> question, would be better?
> regards,
> iustin
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