un-used record wildcards
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?
Regards,
-
Serge Mechveliani
mech...@botik.ru
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Re: un-used record wildcards
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
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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.
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RE: un-used record wildcards
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-boun...@haskell.org
[mailto:glasgow-haskell-users-
| boun...@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.
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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 +, 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-boun...@haskell.org
> [mailto:glasgow-haskell-users-
> | boun...@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.
> | ___
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> | Glasgow-haskell-users@haskell.org
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>
>
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Re: un-used record wildcards
Hi Simon,
I've seen this issue with GHC 6.12.3 (and assumed it was by design).
It occurs with a slight modification of your example:
{-# LANGUAGE RecordWildCards #-}
module Test where
data T = MkT { f,g :: Int }
p x = let MkT{..} = x in f
This example warns about "Defined but not used: `g'" on the line
defining p. I've raised a GHC bug:
http://hackage.haskell.org/trac/ghc/ticket/4411 about this warning.
Thanks, Neil
> 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-boun...@haskell.org
> [mailto:glasgow-haskell-users-
> | boun...@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-us...@haskell.org
> | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
>
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