Re: un-used record wildcards

Thank you. This was with ghc-6.12.2 and RecordWildCards TypeSynonymInstances UndecidableInstances FlexibleContexts FlexibleInstances MultiParamTypeClasses OverlappingInstances, -fwarn-unused-binds -fwarn-unused-matches -fwarn-unused-imports -fno-warn-overlapping-patterns 1) Then, I dropped `,..' in the places where I do not really need other fields, and it has improved. 2) Now, after reading your letter, I tried your example with MkT, and it is all right. Then, I returned `,..' to my code (still the precise initial code is lost, too many changes done), and I cannot obtain now these messages about unused binds. Most probably, this was some other effect with the variables. The program is complex, and I have lost the initial code due to `successfull' attempt with omitting elliplis. I also have to see how the result program will work, this is my first attempt with RecordWildCards, and now, also with NamedFieldPuns. ----------- Mechveliani On Thu, Oct 14, 2010 at 10:06:49PM +0000, Simon Peyton-Jones wrote:

Which version of GHC are you using? GHC 6.12 does not complain about unused variables bound by "..". Try this, which complains about y, but not g.

Simon

{-# LANGUAGE RecordWildCards #-} module Test where

data T = MkT { f,g :: Int }

p (MkT { .. }) y = f

| -----Original Message----- | From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell-users- | bounces@haskell.org] On Behalf Of Serge D. Mechveliani | Sent: 14 October 2010 11:01 | To: Antoine Latter | Cc: glasgow-haskell-users@haskell.org | Subject: Re: un-used record wildcards | | On Wed, Oct 13, 2010 at 01:47:11PM -0500, Antoine Latter wrote: | > On Wed, Oct 13, 2010 at 1:02 PM, Serge D. Mechveliani | wrote: | > > Dear GHC developers, | > > | > > I use the language extension of RecordWildcards, for example, | > >                                f (Foo {foo1 = n, foo2 = m, ..}) = ... | > > | > > But the complier warns about un-used values of  foo3, foo4, | > > probably, due to the extension of | > >                     Foo {foo1 = n, foo2 = m, foo3 = foo3, foo4 = foo4}. | > > | > > In such cases, these warnings look as unneeded. | > > Is it possible to have an un-used binding warnings with exception for | > > wildcards in records? | > > If not, then has it sense to introduce an option? | > > | > | > If you're not using foo3 and foo4, can you not put it the ellipsis? | > that won't cover every case (such as where you're using foo3 but not | > foo4). | > | > Antoine | > | | Indeed, thank you. | It occurs that under RecordWildcards the compiler allows to skip some | record fields in a pattern. | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users