Hi everyone, I have a general program design question, but I can't really think of good examples so it will be a bit vague. There was a discussion on Show not long ago which brought up the problem that there are several ways to "show" a data structure, and it depends on the context (or should I call it a use case?) which of these we actually want, e.g. human readable form, debug information, serialisation for later reading and so on, and one of the solutions was to propose a family of show functions that carry the intended use in their name. However, there are other type classes that are too general to assign such concrete uses to. For instance, if a data structure can have more than one meaningful (and useful) Functor or Monoid instance, what should one do? Should one refrain from instantiating these classes altogether and just use the names of operations directly? If one still decides to pick a certain set of operations as an instance, what are the factors that should guide this decision? What about designing libraries, how much should one prefer standard classes for their interfaces? It seems to me that there is practically no literature on design issues like these, and it would be nice to hear some opinions from experienced Haskellers. Gergely -- http://www.fastmail.fm - The way an email service should be