[Haskell-cafe] Designing a DSL?

Hi, there are numerous examples on how to implement a DSL, but I haven't been able to figure out how to "design" one. I mean I have a pretty good idea of the problem domain, I've coded it over and over again until I got it right. Now I'd like to express that part as a DSL instead of "hard coding" it as before so I can be more prepared if I need to change or amend it. Ideally I'd only have to change the interpreter, right? And that I find to be the really tricky part, how do I *design* a DSL? Günther