Re: curiosity, bug, or just dead code?
On Tue, Sep 11, 2007 at 12:02:26AM +0100, Claus Reinke wrote: > consider this module, which is accepted by ghci-6.6.1: > >module T where >import qualified Prelude as T(length) >import Prelude(length) >length = 0 > > there is no way to refer to either length, as both 'length' and 'T.length' > are ambiguous (ghci complains on uses of either name). but is it a bug? > > then again, everything is implicitly exported, and there are two possible > 'T.length'.. (hugs [20051031] complains about conflicting exports, on > loading T). > > now for the good part: > >module Q where >import T >main = print T.length > > loads fine, and running main returns 0. > >Ok, modules loaded: Q, T. >*Q> main >0 > > so this must be a bug, right? or a matter of interpretation? > > not everything is exported implicitly: imported items, whether unqualified > or qualified and renamed to share the current module as qualifier are not > exported by default. and changing >module T where > > to >module T(module T) where > > leads to conflicting export errors on load in ghci. > > currently, i think ghci is right, and hugs is wrong (note that > my hugs is rather old, though), but it wasn't what i expected. This is a known bug in hugs; quoth the user's guide: In Haskell 98, a missing export list means all names defined in the current module. In Hugs, it is treated as "(module M)", where M is the current module. This is almost the same, differing only when an imported module is aliased as M. Yes, this is a dark corner in H98. Stefan signature.asc Description: Digital signature ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: curiosity, bug, or just dead code?
On Tue, Sep 11, 2007 at 12:02:26AM +0100, Claus Reinke wrote: > consider this module, which is accepted by ghci-6.6.1: > >module T where >import qualified Prelude as T(length) >import Prelude(length) >length = 0 All the GHC behaviour described above follows the Haskell 98 Report. This treatment of omitted export lists is a documented bug in Hugs (section 5.1.4 of the User's Guide). On Mon, Sep 10, 2007 at 06:15:20PM -0700, Tim Chevalier wrote: > This seems like a GHC bug to me. The Haskell 98 report says: > "It is legal for more than one module in scope to use the same > qualifier, provided that all names can still be resolved > unambiguously." (section 5.3.3) I think "all names" there was intended to mean all references in the program (cf 5.5.2). The module exports the locally defined length, and there is no reference to T.length. ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: curiosity, bug, or just dead code?
On 9/10/07, Claus Reinke <[EMAIL PROTECTED]> wrote: > consider this module, which is accepted by ghci-6.6.1: > > module T where > import qualified Prelude as T(length) > import Prelude(length) > length = 0 > > there is no way to refer to either length, as both 'length' > and 'T.length' are ambiguous (ghci complains on uses > of either name). but is it a bug? > This seems like a GHC bug to me. The Haskell 98 report says: "It is legal for more than one module in scope to use the same qualifier, provided that all names can still be resolved unambiguously." (section 5.3.3) and in this case, T.length is ambiguous as you say, so I think the module should fail to typecheck. Cheers, Tim -- Tim Chevalier * catamorphism.org * Often in error, never in doubt "Investing in monopoly software is like investing in crack cocaine; it is the consequential damages, rather than the immediate ones, that kill you in the end." -- Kent Paul Dolan ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
curiosity, bug, or just dead code?
consider this module, which is accepted by ghci-6.6.1: module T where import qualified Prelude as T(length) import Prelude(length) length = 0 there is no way to refer to either length, as both 'length' and 'T.length' are ambiguous (ghci complains on uses of either name). but is it a bug? then again, everything is implicitly exported, and there are two possible 'T.length'.. (hugs [20051031] complains about conflicting exports, on loading T). now for the good part: module Q where import T main = print T.length loads fine, and running main returns 0. Ok, modules loaded: Q, T. *Q> main 0 so this must be a bug, right? or a matter of interpretation? not everything is exported implicitly: imported items, whether unqualified or qualified and renamed to share the current module as qualifier are not exported by default. and changing module T where to module T(module T) where leads to conflicting export errors on load in ghci. currently, i think ghci is right, and hugs is wrong (note that my hugs is rather old, though), but it wasn't what i expected. claus ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
