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

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?

I'm not sure what you mean by falling back on Show/Read instances, but this seems like a typical generic programming problem. Recent releases include the EMGM and SYB libraries for generic programming. -- Johan Jeuring