[Haskell-cafe] Serialising types with existential data constructors
avatar at hot.ee
Tue Sep 12 08:28:28 EDT 2006
I've been using existentially quantified data constructors like
> data Box = forall a. Cxt a => Box a
quite successfully for a while. But now I am trying to implement the
Load/Save mechanism and getting stuck with that. It's not hard to write
a Box into a file, but how do I get it back?
Has anyone solved the same problem before? I would be very thankful
for any suggestions!
If Template Haskell would support finding out all instances of a given
class, I could generate a function that would map Names of types to
appropriate Box readers. In the file I would write entries like
<NameOfTypeInTheBox> : <BoxContents>
But sadly, TH doesn't allow that yet.
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