Scott Lawrence wrote: > More specifically, I have > > class Model m a | m -> a where ... > class Entropy d where ... > instance (Model m a) => Entropy m where ... > > The first line requires MultiParamTypeClasses and > FunctionalDependencies... the third > requires UndecidableInstances... > Is this likely to cause a problem?
Yes. You almost never want to use UndecidableInstances when writing practical programs in Haskell. When GHC tells you that you need them, it almost always means that your types are poorly designed, usually due to influence from previous experience with OOP. Your best bet is to step back and think again about the problem you are trying to solve. What is the best way to formulate the problem functionally? That will lead you in the right direction. Please feel free to share more details about what you are trying to do. We would be happy to help you work out some good directions. Regards, Yitz _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
