Dear GHC developers, people, Do you agree that there exists such a problem for a programmer as recalling exported instances? Have Haskell and/or GHC some constructs and tools to help the programmer to recall the exported instances for a module? Could GHC support the instance export messages for each module? In Haskell-98, the exported instances cannot be named explicitly in the export list. Right? But for easier understanding of a program, it is desirable to allow to name (in a short form) instances in the export list. For this reason, I add comments, and write the export like this: module Poly (WithHead(..), WithTail(..), -- classes Mon(..), Polynomial(..), lc, polMons -- , instances -- for Mon: WithHead, List; -- for Polynomial: WithHead, Cast Polynomial Mon ) The comment of kind "-- , instances ..." helps to recall which instances are exported, without inspecting all the (lengthy) module source. But when the programmer changes the source, one often forgets to add/remove the needed comments about instances. I often forget them (maybe, lazy to recall) when I move pieces of code between modules. So, I suggest the following feature for GHC. 1. To allow the export declarations of kind instance {<type>} (maybe to suggest this for Haskell ?) 2. If the module under compilation has the word `instance' in its export list, then ghc finds the difference set diff for the exported instance kinds eKinds and the instance kinds nKinds named in the export list. If not $ null diff, it issues the message: "Warning: the exported instance kinds and the instance kinds named in the export differ in the following items: ...". Seeing such a message, the user corrects the export list in the source according to diff. For the export list and for their messages, it is probably better to use a short denotation: the instance kind rather than full instance declaration. In the instance kind, the part of "(...) =>" is skipped. What people think of this suggestion? Thank you in advance for your notes and help, ----------------- Serge Mechveliani mechvel@botik.ru