Claus Reinke wrote:
Actually, standalone deriving doesn't really solve the boilerplate boilerplate problem. My original complaint here is that I don't want to explicitly declare a deriving (Data,Typeable) for every type used somewhere inside a larger type I am using. In this particular case, I am using SYB to autogenerate/autoparse XML. The Atom/RSS datatype has a lot of elements in it. Having to do an explicit declaration of deriving (Data,Typeable) for each of them is just a tremendous beat-down no matter where I do it.
A simple solution to the problem is just to have the compiler automatically derive Data and Typeable for all classes.
it still sounds as if you might want to follow Neil's suggestions about using Data.Derive, which does seem to have a derive-this-for-all feature.
The problem with Data.Derive is that I now have a pre-processor cycle as part of my build process. Automatic and universal Data and Typeable instance deriving should just be built into Haskell. I totally agree that, if you don't have this deriving by default, it is totally useful to be able to derive in a location different from where the type is declared, but that is a separate issue. My main point is that Data and Typeable should always be there without extra futzing on the part of the programmer. Speaking of which, any thoughts on fixing my SYB code in the other thread? -Alex-