The monads design is used in Data.Map i.e. lookup :: (Monad m, Ord k) => k -> Map k a -> m a
and I think that this will be more consistent. On 5/23/08, Ross Paterson <[EMAIL PROTECTED]> wrote: > On Fri, May 23, 2008 at 09:03:29AM +0200, Krasimir Angelov wrote: > > Alternatively I can use monad with failure. In other words, there are > > two possibilities: > > > > 1. Use error ".." and types like: TreeLoc a -> TreeLoc a > > 2. Use monad and type like: Monad m => TreeLoc a -> m (TreeLoc a) > > I'd suggest that TreeLoc a -> Maybe (TreeLoc a) is better than the > second version. The problem with using Monad(fail) is that it hides > possible runtime errors among testable conditions. With 1. you can > at least search the code for occurrences of the dangerous function. > With the Monad version you need to consider the type of each use to know > whether it is dangerous. > _______________________________________________ > Haskell-Cafe mailing list > [email protected] > http://www.haskell.org/mailman/listinfo/haskell-cafe > _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
