2009/11/3 Neil Brown <nc...@kent.ac.uk>: > Hi, > > I was thinking about some of my code today, and I realised that where I have > an arrow in my code, A b c, the type (A b) is also a functor. The > definition is (see > http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-Arrow.html): > > fmap = (^<<) > -- Or, in long form: > fmap f x = arr f <<< x > > Out of curiosity, and since this is a typical haskell-cafe question, does > this definition of fmap hold for all arrows? > > And is there a wiki page somewhere that has a table of all of these Haskell > type-classes (Functor, Monad, Category, Arrow, Applicative and so on), and > says that if you are an instance of class A you must have some corresponding > instance of B? (e.g. all Monads are Functors and Applicatives) I'm fairly > certain my arrow isn't a Monad or Applicative, although of course it must be > a Category, given the type-class dependency, but it would be nice when using > one of these things to see what other instances you should automatically > supply. >
What about the Typeclassopedia (http://haskell.org/sitewiki/images/8/85/TMR-Issue13.pdf)? > Thanks, > > Neil. > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- Eugene Kirpichov Web IR developer, market.yandex.ru _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
