On 8 February 2010 11:16, John Lato
Regardless, I think this is a valid approach. By thinking of data in terms of Functor, Traversable, etc., one can recognize these patterns. Even if Binding is part of a larger syntax tree and can't reasonably be made polymorphic, creating an fmap-like function to do what the OP requested is IMHO simple and idiomatic Haskell. Using Generics then simplifies the implementation.
Hi John, Most definitely! - 'making a functor' is one of the strategies / patterns to consider when designing data types. It would be nice if there was a reference listing and defining such strategies. Phantom types are another strategy (well, maybe a family of strategies if you look closely), as is the de-normalisation by 'moving the sum' that I mentioned previously in the thread, albeit on a smaller scale. Best wishes Stephen