Hello, I think that the H98 change was a good one. Qualified names should only be used in _uses_ of variables (to disambiguate) and not in definitions because (hopefully) there is nothing to disambiguate in a definition.
By the way, method definitions already have a distinction between what is on the LHS and what is on the RHS. For example, consider the following instance: instance Show a => Show (Maybe a) where show Nothing = "Nothing" show (Just a) = "Just " ++ show a Here "show" is not a recursive function because the "show" on the RHS is different from the "show" on the LHS. So my preference is to keep the status quo on this issue. -Iavor On Fri, Apr 25, 2008 at 7:09 AM, Claus Reinke <[EMAIL PROTECTED]> wrote: > consider Haskell 98 report, section 4.3.2 "Instance Declarations": > > The declarations d may contain bindings only for the class methods of C. > It is illegal to give a binding for a class method that is not in scope, but > the name under which it is in scope is immaterial; in particular, it may > be a qualified name. (This rule is identical to that used for subordinate > names in export lists --- Section 5.2.) For example, this is legal, even > though range is in scope only with the qualified name Ix.range. > module A where > import qualified Ix > > instance Ix.Ix T where > range = ... > > i consider this confusing (see example at the end), but even > worse is that the reference to 5.2 appears to rule out the use of qualified > names when defining instance methods. > > while this abbreviation of qualified names as unqualified names when > unambiguous may be harmless in the majority of cases, it > seems wrong that the more appropriate explicit disambiguation > via qualified names is ruled out entirely. > i submit that 4.3.2 should be amended so that qualified names are permitted > when defining instance methods. > > here's an example to show that the unambiguity holds only on the > lhs of the method definition, and that the forced use of unqualified > names can be confusing: > > module QI where > import Prelude hiding (Functor(..)) > import qualified Prelude (Functor(..)) > data X a = X a deriving Show > instance Prelude.Functor X where fmap f (X a) = X (f a) > where q = (reverse fmap,Prelude.fmap not [True],reverse QI.fmap) > fmap = "fmap" > > note that there are two unqualified uses of 'fmap' in the instance > declaration, referring to different qualified names: > - in the lhs, 'fmap' refers to 'Prelude.fmap', which isn't in scope > unqualified, only qualified > > - in the rhs, 'fmap' refers to 'QI.fmap' > > claus > > > _______________________________________________ > Haskell-prime mailing list > Haskell-prime@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-prime > _______________________________________________ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
