[Haskell-cafe] automatically deriving Map and Filter on datatypes etc.

[Neil Mitchell]

Hi

>  PS Why isn't Functor derivable?

Derive can do it: http://www.cs.york.ac.uk/~ndm/derive

I believe that Twan (the author of Functor deriving in Derive) is
trying to get this suggested for Haskell' as a proper deriving.

As for the original question, Uniplate will certainly do map, and will
probably help with filter - as the definition of Filter is not obvious
given the type. And you can have automatic deriving with Uniplate (see
PlateData in the paper or the module structure)
http://www.cs.york.ac.uk/~ndm/uniplate

Thanks

Neil