On 20 Jan 2015, at 11:20, Björn Peemöller wrote:
The reason is the usage of foldr, which changed its type from
foldr :: (a - b - b) - b - [a] - b -- GHC 7.8.4
to
foldr :: Foldable t = (a - b - b) - b - t a - b -- GHC 7.10.1
Thus, the use of foldr is now ambiguous. I can fix this by
I'd like to be able to use the UNPACK pragma on an existentially quantified
datatype. So as in the below example:
{-# LANGUAGE ExistentialQuantification #-}
data Foo = forall a. Show a = Foo !a
instance Show Foo where
show (Foo a) = Foo! ++ show a
data Bar =
Bar {-# UNPACK #-} !Foo
There is a limited set of situations where the new signatures can fail to
infer, where it would infer before.
This can happen when you construct a Foldable/Traversable value using
polymorphic tools (like Read) that were previously instantiated for list,
but where since foldr et al. are now
I just discovered that the following program compiled fine using GHC
7.8.4 but was rejected by GHC 7.10.1-rc1:
~~~
data List a = Nil | Cons a (List a)
instance Read a = Read (List a) where
readsPrec d s = map convert (readsPrec d s)
where
convert (xs, s2) = (foldr Cons Nil xs, s2)
~~~
Interesting question. I managed to trace this to:
compiler/basicTypes/MkId.hs:699
isUnpackableType fam_envs ty
| Just (tc, _) - splitTyConApp_maybe ty
, Just con - tyConSingleAlgDataCon_maybe tc
, isVanillaDataCon con
= ok_con_args (unitNameSet (getName tc)) con
| otherwise
= False
On Tue, Jan 20, 2015 at 6:45 PM, Edward Kmett ekm...@gmail.com wrote:
I can at least say that the incident rate for cases seems to be very low,
especially when it is contrasted against the pain users have had with using
the existing Foldable/Traversable imports where virtually everything in
I've added it as https://ghc.haskell.org/trac/ghc/ticket/10009
On Tue, Jan 20, 2015 at 11:23 AM, Richard Eisenberg e...@cis.upenn.edu wrote:
After quite a bit of thought, I agree that this is a regression and that the
original program should be accepted.
Make a bug report!
Thanks,
Richard
After quite a bit of thought, I agree that this is a regression and that the
original program should be accepted.
Make a bug report!
Thanks,
Richard
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Simon,
This was fixed some time back. I combed the code base looking for other busy
loops and there are no more. I commented out the code that runs the I2C +
Machines + IO stuff, and only left the GUI code. It appears that just the
wxhaskell part of the program fails to start. This matches a
On Tue, Jan 20, 2015 at 9:00 AM, Kim-Ee Yeoh k...@atamo.com wrote:
There are few reports because the change hasn't affected the dark majority
yet. RC builds are used by a tiny fraction. There's a long tail of users
still on 7.6, 7.4, 7.2, and 6.x.
We've been actively testing since the
Hello!
What is a hole?
This program fails to compile:
main = _exit 0
I get this error message:
ex.hs:1:8:
Found hole ‘_exit’ with type: t
Where: ‘t’ is a rigid type variable bound by
the inferred type of main :: t at ex.hs:1:1
Relevant bindings include main :: t
On Tue, Jan 20, 2015 at 1:36 PM, Volker Wysk vertei...@volker-wysk.de
wrote:
What is a hole?
https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/typed-holes.html
When I replace _exit with foo, it produces a not in scope error, as
expected. What is special about _exit? It doesn't
Hello Volker,
All identifiers prefixed with an underscore are typed holes,
see:
https://downloads.haskell.org/~ghc/7.8.3/docs/html/users_guide/typed-holes.html
Edward
Excerpts from Volker Wysk's message of 2015-01-20 10:36:09 -0800:
Hello!
What is a hole?
This program fails to compile:
They are described at these two links:
https://www.haskell.org/haskellwiki/GHC/Typed_holes
https://downloads.haskell.org/~ghc/7.8.1-rc1/docs/html/users_guide/typed-holes.html
Essentially, identifiers that are not otherwise in scope and consist of an
underscore or that have a trailing underscore
My guess would be that either
- a thread is in a non-allocating loop
- a long-running foreign call is marked unsafe
Either of these would block the other threads. ThreadScope together
with some traceEventIO calls might help you identify the culprit.
Cheers,
Simon
On 20/01/2015 15:49,
Am Montag, 19. Januar 2015, 23:32:09 schrieben Sie:
On Mon, Jan 19, 2015 at 11:14 PM, Volker Wysk vertei...@volker-wysk.de
wrote:
I've uploaded my library to Hackage, and now I'm trying to install it via
cabal:
At a guess, the index has not yet been updated --- you may need to wait
some
I like this proposal: if you're explicit about an import that
would otherwise be implicit by Prelude, you shouldn't get a
warning for it. If it is not already the case, we also need to
make sure the implicit Prelude import never causes unused import
errors.
Edward
Excerpts from Edward Kmett's
I was assuming that the list was generated by doing more or less the same
check we do now. I haven't looked at the code for it.
If so, then it seems it wouldn't flag a now-unnecessary Data.Traversable
dependency for instance. At least not without rather significant retooling.
I might be off in
It isn't without a cost. On the down-side, the results of
-ddump-minimal-imports would be er.. less minimal.
On Tue, Jan 20, 2015 at 6:47 PM, Edward Z. Yang ezy...@mit.edu wrote:
I like this proposal: if you're explicit about an import that
would otherwise be implicit by Prelude, you
On Tue, Jan 20, 2015 at 3:02 PM, Herbert Valerio Riedel h...@gnu.org wrote:
I'm a bit confused, several past attoparsec versions seem to build just
fine with GHC 7.10:
https://ghc.haskell.org/~hvr/buildreports/attoparsec.html
were there hidden breakages not resulting in compile errors?
Unless it behaves differently in GHC than GHCi, you can still use underscore
prefixed identifiers, provided they are in scope. I only get a type hole
message if the identifier isn't defined anywhere else.
let _x = 2
_x
2
_y
Found hole '_y' with type: t
...
--
View this message in context:
Sure.
Adding it to the CHANGELOG makes a lot of sense. I first found out about it
only a few weeks ago when Herbert mentioned it in passing.
Of course, the geek in me definitely prefers technical fixes to human ones.
Humans are messy. =)
I'd be curious how much of the current suite of warnings
Hello Bryan,
On 2015-01-20 at 23:17:01 +0100, Bryan O'Sullivan wrote:
[...]
For the record, it took me almost an hour to update attoparsec to fix all
the various regressions, or to put it more charitably changes, introduced
in GHC 7.10. I have twenty-something other packages to go through. I
I don't see why that would be the case: we haven't *excluded* any
old import lists, so -ddump-minimal-imports could still
take advantage of Prelude in a warning-free way.
Edward
Excerpts from Edward Kmett's message of 2015-01-20 16:36:53 -0800:
It isn't without a cost. On the down-side, the
Yes, I fixed it on the train. Most helpful. Busy tomorrow but I should have a
fix committed by the end of the week
Simon
| -Original Message-
| From: Glasgow-haskell-users [mailto:glasgow-haskell-users-
| boun...@haskell.org] On Behalf Of Richard Eisenberg
| Sent: 20 January 2015 16:24
Building -Wall clean across this change-over has a big of a trick to it.
The easiest way I know of when folks already had lots of
import Data.Foldable
import Data.Traversable
stuff
is to just add
import Prelude
explicitly to the bottom of your import list rather than painstakingly
exclude
Simon,
The code below hangs on the frameEx function.
But, if I change it to:
f - frameCreate objectNull idAny linti-scope PMBus Scope Tool
rectZero (frameDefaultStyle .|. wxMAXIMIZE)
it will progress, but no frame pops up, except once in many tries. Still hangs,
but progresses
Just use exit_ or something instead. Typed holes are a *really useful*
mechanism.
On Tue, Jan 20, 2015 at 3:51 PM, migmit mig...@gmail.com wrote:
DON'T DO THAT!
Seriously, turn off compile-time type checking completely just to start an
identifier with an underscore???
Отправлено с iPad
20
FWIW- you can think of a 'hole' as a not in scope error with a ton of
useful information about the type such a term would have to have in order
to go in the location you referenced it.
This promotes a very useful style of type-driven development that is common
in Agda, where you write out your
i think ben gamari hit similar/related issues with the lib usb bindings in
7.8, and i believe some / all of them are fixed in 7.10
(i could be mixing things up though)
On Tue, Jan 20, 2015 at 10:43 PM, Michael Jones m...@proclivis.com wrote:
Simon,
The code below hangs on the frameEx
On 2015-01-21 at 00:27:39 +0100, Edward Z. Yang wrote:
Hello Edward,
Shouldn't we publicize this trick? Perhaps in the changelog?
Fwiw, I've added that workaround/recipe to
https://ghc.haskell.org/trac/ghc/wiki/Migration/7.10#GHCsaysTheimportof...isredundant
feel free to improve the
Hello!
I've found what went wrong: _exit wasn't in scope, so it was interpreted to
be a typed hole.
Thanks
Volker
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You can get typed holes to compile with a warning and a runtime error with
the -fdefer-type-errors flag, if that's what you want.
However, it's perfectly legal to use identifiers which look like typed
holes. This works fine on 7.8.3ghc:
_exit = print
main = _exit 0
On Tue, Jan 20, 2015 at 11:25
Wrongly, as it turned out. Sorry! The problem remains.
On Tue, Jan 20, 2015 at 2:37 PM, David Feuer david.fe...@gmail.com wrote:
And I've closed it as worksforme. I couldn't reproduce the problem
with 7.11.20150103.
On Tue, Jan 20, 2015 at 11:42 AM, adam vogt vogt.a...@gmail.com wrote:
I've
DON'T DO THAT!
Seriously, turn off compile-time type checking completely just to start an
identifier with an underscore???
Отправлено с iPad
20 янв. 2015 г., в 21:39, Alex Hammel ahamme...@gmail.com написал(а):
You can get typed holes to compile with a warning and a runtime error with
Hi!
Am Dienstag, 20. Januar 2015, 13:44:01 schrieben Sie:
The leading underscore invokes the typed holes extension. If you want to
use such names, you'll need {-# LANGUAGE NoTypedHoles #-} as the first line
of the source file.
I get this error, when I use {-# LANGUAGE NoTypedHoles #-}:
And I've closed it as worksforme. I couldn't reproduce the problem
with 7.11.20150103.
On Tue, Jan 20, 2015 at 11:42 AM, adam vogt vogt.a...@gmail.com wrote:
I've added it as https://ghc.haskell.org/trac/ghc/ticket/10009
On Tue, Jan 20, 2015 at 11:23 AM, Richard Eisenberg e...@cis.upenn.edu
The only reference to a NoTypedHoles extension google can find is this
thread. Odd.
On Tue, Jan 20, 2015 at 11:22 AM, Volker Wysk vertei...@volker-wysk.de
wrote:
Hi!
Am Dienstag, 20. Januar 2015, 13:44:01 schrieben Sie:
The leading underscore invokes the typed holes extension. If you want
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