Hi Tim,
Your example seems like a perfect fit for functional dependencies.
On Thu, Sep 11, 2008 at 3:36 AM, Tim Docker
Well, it's a library that others might use, so I would prefer to avoid using language extensions, especially functional deps which I don't understand, and which seem to have an uncertain future.
I completely agree with you that it is a good idea to stick to Haskell'98 when you can, especially in library code, so you'll have to decide if you really want to use the class. As for not understanding functional dependencies, it sounds like you are not giving yourself enough credit. Your previous comment basically contains the definition of a functional dependency: | But the above is, I think, too general for my needs. I don't want | to be able to generate Renderables of different type b for a single input | type a. This is all there is to a fun. dep., from a programmer's perspective---it adds a constraint on the instances one can declare for a given multi-parameter type class. Hope this helps, -Iavor