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

On Sun, Mar 1, 2009 at 6:42 PM, Martin Huschenbett wrote:

Hi,

you could do something like

...

instance (Show a,Read a) => Binary a where  put = put . show  get = fmap read get

But then you will need the following language extensions: FlexibleInstances, OverlappingInstances, UndecidableInstances

Well, isn't there a good chance it'll end up picking that instance even when a more specific one is available, then? I think the problem here is that I don't know of any way to inform GHC that any particular instance is "less specific".