[Haskell-cafe] Supplying a default implementation for a typeclass based on another class

Lennart Augustsson lennart at augustsson.net
Sat Feb 28 06:55:16 EST 2009

If you were writing your own Binary class you could simply make Show
and Read superclasses of Binary and it would be trivial to have
default implementations based on Show and Read.

  -- Lennart

On Sat, Feb 28, 2009 at 10:59 AM, Svein Ove Aas <svein.ove at aas.no> wrote:
> I'm in the process of writing a distributed filesystem (in haskell,
> yay), which of course means I'm using Binary for de/serialization.
> Now, that's fine enough, but for simplicity (and for wireshark), I'd
> like to be able to have Binary fall back on an instance based on
> Show/Read for any type that lacks any other Binary instance..
> Well, I understand why this would be somewhere between extremely hard
> and impossible in haskell '98, but I'm not entirely up on all the
> extensions, so I thought I'd ask - given every extension implemented
> in ghc 6.10.1, is there any reasonable way to do this?
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