Hi,
Compiling the following program (Bug.hs):
module Main where
import System.Console.Readline
main =
do ms - readline Hi
print ms
Using GHC 6.2.2 on Windows XP, using the command line:
ghc --make Bug -o bug
Produces the following message:
Chasing modules from: Bug
Compiling
Hi,
Take a look at the following program, making use of
derivable type classes.
module Bug where
import Data.Generics
class Foo a where
foo :: a - Int
foo{| Unit |}_ = 1
foo{| a :*: b |} _ = 2
foo{| a :+: b |} _ = 3
instance Foo [a]
GHC 6.2.2 produces the following error
Bugs item #1069656, was opened at 2004-11-19 19:57
Message generated for change (Settings changed) made by simonmar
You can respond by visiting:
https://sourceforge.net/tracker/?func=detailatid=108032aid=1069656group_id=8032
Category: None
Group: None
Status: Closed
Resolution: None
Priority: 5
Yes, you guessed right. Your generic class declaration gives rise to
instance declarations like
| instance (Foo a, Foo b) = Foo (a :*: b) where
| foo _ = 2
You suggest that it could be cleverer about guessing the context for the
instance decl, and that would make sense. But this'd then be
Bugs item #1071030, was opened at 2004-11-22 15:45
Message generated for change (Tracker Item Submitted) made by Item Submitter
You can respond by visiting:
https://sourceforge.net/tracker/?func=detailatid=108032aid=1071030group_id=8032
Category: None
Group: None
Status: Open
Resolution: None
On 16 November 2004 17:16, Koen Claessen wrote:
Compiling the following program (Bug.hs):
module Main where
import System.Console.Readline
main =
do ms - readline Hi
print ms
Using GHC 6.2.2 on Windows XP, using the command line:
ghc --make Bug -o bug
Produces
Dear GHC team,
As there exists, say,Data.mapSet,
is this natural to provide also filterSet
?
-
Serge Mechveliani
[EMAIL PROTECTED]
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On 20 November 2004 23:02, Benjamin Franksen wrote:
I am using Foreign.Concurrent.newForeignPtr and touchForeignPtr
inside the finalizers to express liveness dependencies as hinted to
by the documentation. This doesn't seem to work, though, or at least
I can't see what I've done wrong. I
Some thoughts on this,
Whilst I agree that finalizers are best avoided, it must be possible to
order the finalizers for running on exit... Perhaps a simple multi-pass
algorith would do? (ie: run all finalizers that do not refer to other
objects
with finalizers - repeat until no objects with
On 18 November 2004 20:31, Christian Maeder wrote:
calling unlit on a DOS file fails, whereas hugs is able to process the
same file (under unix).
Christian
Prelude readFile Test.lhs = putStrLn . show
\r\n module Test where\r\n\r\n
Prelude :l Test.lhs
Test.lhs line 2: unlit: Program
Hi there folks,
once again, I've got a question related to Happy (I've got version 1.13 at
the moment).
Maybe, it's even more a question on formal languages, but well...
How can I write a grammar that can cope with user-defined operators (of
different precedences/associativities) and compound
On 21 November 2004 00:56, Isaac Jones wrote:
The systems that would want to do this kind of thing, such as Debian,
have other mechanisms for deciding whether packages conflict, etc.
IIRC, this is the argument I just used against adding support for
multiple libraries in Cabal, so I guess I
Keean Schupke wrote:
[...]
Whatever happens I think it must make sure all system resources allocated
by a program are freed on exit - otherwise the machine will have a resource
leak and will need rebooting eventually.
That's an OS task IMHO, not really the task of an RTS. Looks like you're
working
Nope there are some unix resources that c exit routines do not free
like semaphores.
Sven Panne wrote:
Keean Schupke wrote:
[...]
Whatever happens I think it must make sure all system resources
allocated
by a program are freed on exit - otherwise the machine will have a
resource
leak and will
On Monday 22 November 2004 14:45, Simon Marlow wrote:
On 20 November 2004 23:02, Benjamin Franksen wrote:
I am using Foreign.Concurrent.newForeignPtr and touchForeignPtr
inside the finalizers to express liveness dependencies as hinted to
by the documentation. This doesn't seem to work,
If finalizers are not the right thing, what else is?
I've found that when writing an interface to a C library that requires
resource management, it's much better to use the withX (see
Control.Exception.bracket) style of function than to use finalizers -
programs are much easier to reason about
Abraham Egnor wrote:
I've found that when writing an interface to a C library that requires
resource management, it's much better to use the withX (see
Control.Exception.bracket) style of function than to use finalizers -
programs are much easier to reason about and debug.
... and have a much more
Keean Schupke wrote:
Nope there are some unix resources that c exit routines do not free
like semaphores.
Which library/OS calls do you mean exactly? I always thought that files
are the only resources surviving process termination.
Cheers,
S.
___
On Mon, 2004-11-22 at 17:48 +0100, Frank-Andre Riess wrote:
Hi there folks,
once again, I've got a question related to Happy (I've got version 1.13 at
the moment).
Maybe, it's even more a question on formal languages, but well...
How can I write a grammar that can cope with user-defined
Semaphores (SYSV style) are not freed automatically. Currenly I am using
C's at_exit funtion (which is even called on a signal)... Perhaps this
is the
way to deal with foreign resources... bracket notation and at_exit to clean
up on signals?
Keean.
Sven Panne wrote:
Keean Schupke wrote:
Nope
On 2004 nov 22, at 17:48, Frank-Andre Riess wrote:
Hi there folks,
once again, I've got a question related to Happy (I've got version
1.13 at
the moment).
Maybe, it's even more a question on formal languages, but well...
How can I write a grammar that can cope with user-defined operators (of
On Monday 22 November 2004 18:55, Sven Panne wrote:
Abraham Egnor wrote:
I've found that when writing an interface to a C library that requires
resource management, it's much better to use the withX (see
Control.Exception.bracket) style of function than to use finalizers -
programs are
Keean Schupke wrote:
C exit routines aren't responsible for freeing OS resources; the OS
is.
The fact that the SysV IPC objects aren't freed on exit is
intentional; they are meant to be persistent. For the same reason, the
OS doesn't delete upon termination any files which the
Although, this does remind me.
A suitable atexit-equivalant in the haskell libraries would be much appreciated.
John
--
John Meacham - repetae.netjohn
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On Friday 19 Nov 2004 2:27 pm, Benjamin Franksen wrote:
Implicit parameters are evil, agreed. Their deficiencies should be added
as a warning to the docs (with many exclamation marks).
Well I dunno. Maybe whatever's currently wrong with them can be fixed up.
But I can't say they're something
Adrian Hey wrote:
Just repeating this again and again doesn't make it any more true.
Ditto... I for one think the best solution is to use the language as
intended and pass the values as function arguments. As pointed out
on this list - the only possible situation where you cannot do this is
when
On Mon, Nov 22, 2004 at 07:27:44PM +0100, Lennart Augustsson wrote:
[snip]
I admit there are proper uses of global variables, but they are very
rare. You have not convinced me you have one.
-- Lennart
It's with some trepidation I bring a problem as a total newbie, but I've
been
On Mon, 2004-11-22 at 23:34, John Velman wrote:
In a nutshell:
I want to use the old value of a tag to compute the new value, in a
callback,
I want to access the tag from other callbacks, and
I want to the value to a mutable list from within the callback.
I'd
On Saturday 20 November 2004 10:47, Serge D. Mechveliani wrote:
Is such a function familia to the Haskell users?
foldlWhile :: (a - b - a) - (a - Bool) - a - [b] - a
Maybe this link is of interest to you:
http://okmij.org/ftp/Haskell/#fold-stream
Ben
--
Top level things with identity are
Once again, the Haskell class system is proving rather subtle for me.
On this occasion, I'm getting an overlapping class instance error which I
think should be fully disambiguated by the supplied class context.
The code below (end of message) is a .lhs file that reproduces the problem
in Hugs,
Instance selection and thereby overlapping resolution
is *independent* of constraints. It is defined to be purely
syntactical in terms of instance heads. See the HList paper
for some weird examples.
Ralf
Graham Klyne wrote:
The reported overlapping instance is [Char], which I take to be
derived
[Switching to Haskell-cafe]
At 11:26 22/11/04 +, you wrote:
I would ask an alternative question - is it possible to live without
unsafePerformIO? I have never needed to use it!
I have used it once, with reservations, but at the time I didn't have the
time/energy to find a better solution.
Obviously without knowing the details I am speculating, but would it not
be possible
to do a first pass of the XML and build a list of files to read (a pure
function) this returns
its result to the IO monad where the files are read and concatenated
together, and passed
to a second (pure
On Monday 22 November 2004 23:22, Keean Schupke wrote:
It seems to me that as unsafePerformIO is not in the standard and only
implemented on some
compilers/interpreters, that you limit the portability of code by using
it, and that it is best avoided. Also as any safe use of unsafePerformIO
Benjamin Franksen writes:
If a foreign function (e.g. from a C library) is really
pure, then I see no way to tell that to the compiler
other than using unsafePerformIO.
What's the problem with importing it with a pure signature?
Like this:
foreign import ccall unsafe sin :: CDouble -
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