Manuel said earlier that the source of the problem here is foo's
ambiguous type signature
(I'm switching back to the original, simplified example).
Type checking with ambiguous type signatures is hard because the type
checker has to guess
types and this guessing step may lead to too many (ambigu
On Wed, 9 Apr 2008, Manuel M T Chakravarty wrote:
Sittampalam, Ganesh:
No, I meant can't it derive that equality when matching (Id a) against
(Id b)? As you say, it can't derive (a ~ b) at that point, but (Id a ~
Id b) is known, surely?
No, it is not know. Why do you think it is?
Well,
Chaddaï Fouché:
2008/4/8, Manuel M T Chakravarty <[EMAIL PROTECTED]>:
You need to write the instance as
instance (b ~ TheFoo a, Foo a) => Bar (Either a b) where
bar (Left a) = foo' a
bar (Right b) = foo' (foo b :: a)
If you do that, the program compile, but res still raise a panic in
On 8 Apr 2008, at 7:06 PM, Dan Weston wrote:
Richard A. O'Keefe wrote:
On 8 Apr 2008, at 7:15 am, Dan Weston wrote:
[1] Yes, I know that "conciseness" is the much more common and
accepted word for this, but if we can say "precision",
"decision", and "incision", then it seems foolish to not
Sittampalam, Ganesh:
Manuel Chakravarty wrote:
Ganesh Sittampalam:
On Mon, 7 Apr 2008, Manuel M T Chakravarty wrote:
Ganesh Sittampalam:
The following program doesn't compile in latest GHC HEAD, although
it does if I remove the signature on foo'. Is this expected?
Yes, unfortunately, this
Richard A. O'Keefe wrote:
On 8 Apr 2008, at 7:15 am, Dan Weston wrote:
[1] Yes, I know that "conciseness" is the much more common and
accepted word for this, but if we can say "precision", "decision", and
"incision", then it seems foolish to not also use "concision". I will
henceforth take on
On 8 Apr 2008, at 7:15 am, Dan Weston wrote:
[1] Yes, I know that "conciseness" is the much more common and
accepted word for this, but if we can say "precision", "decision",
and "incision", then it seems foolish to not also use "concision". I
will henceforth take on this quixotic quest to p
graphics-drawingcombinators 0.1 has just been uploaded to hackage:
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/graphics-drawingcombinators-0.1
Have you ever tried to write a simple 2D interface or game but found:
* wxHaskell and gtk2hs are hard to install and learn
* SDL does
Bug report:
I am using IE6. The "Powered by" bar at the bottom does not reposition as I
scroll down. So there is a small portion on the page always masked by the
"Powered by" bar.
Nice work. Great google-like speed...
Steve
On 4/8/08, Timo B. Hübel <[EMAIL PROTECTED]> wrote:
>
> Hello,
>
> than
On 2008.04.08 15:19:12 -0500, John Goerzen <[EMAIL PROTECTED]> scribbled 1.1K
characters:
> On Mon April 7 2008 9:31:04 pm [EMAIL PROTECTED] wrote:
> >
> > Well, changing the deps at least would be a good idea.
>
> Right. I've uploaded a new version of hpodder to hackage that will require
> the c
Hello,
thanks for all the feedback so far! We have just deployed some minor updates
for Hayoo!, mainly improving the ranking mechanism. It should now prefer
modules from the Prelude as well as functions exactly matching the query
terms.
Additionally, we have started a blog about Hayoo! and Hol
Yes, sorry I should have read the post more carefully. I was talking
specifically the use of => in class declarations, and this is a good
example of how inconsistent the notation seems to me.
It is in the class declaration that the arrow is backwards. (I imagine
this decision was more syntacti
On Tue, Apr 8, 2008 at 11:05 PM, PR Stanley <[EMAIL PROTECTED]> wrote:
>
>
> >
> > > What is the difference between
> > >
> > >data T0 f a = MkT0 a
> > >instance Eq (T0 f a) where ...
> > >
> > >and
> > >
> > >data T0 f a = MkT0 a
> > >instance Eq a => Eq (T0 f a) where ...
What is the difference between
data T0 f a = MkT0 a
instance Eq (T0 f a) where ...
and
data T0 f a = MkT0 a
instance Eq a => Eq (T0 f a) where ...
The second one says that "TO f a" is only an instance of "Eq" if "a"
is, while the first says that "TO f a" is an instanc
On 2008-04-07 18:57:39 -0400, [EMAIL PROTECTED] wrote:
> So almost certainly the issue is that HaXml has updated and changed
> things around in a way that broke Hpodder; not surprising, since
> HaXml-1.19.2 is as recent as 14 January 2008, and Goerzen may simply
> not have updated and discovered t
On Tue April 8 2008 3:21:34 pm Karl Hasselström wrote:
> http://www.haskell.org/haskellwiki/Package_versioning_policy seems to
> have something relevant to say. build-depends: HaXml >= 1.13.3 && <
> 1.14 ought to do the trick, since any changes in the published
> interface are supposed to be accom
Hello all.
On Wed, 09 Apr 2008 05:36:40 Paul Brown wrote:
> Hi, Bjorn and Uwe --
>
> > > this is a known problem with HTTP package (version 3001.0.4).
> > > Paul Brown has described this somewere in his blog.
> > > (http://mult.ifario.us/t/haskell), but my firefox only shows
> > > an incom
On 2008-04-07 20:20:24 -0500, John Goerzen wrote:
> On Monday 07 April 2008 5:57:39 pm [EMAIL PROTECTED] wrote:
>
> > So almost certainly the issue is that HaXml has updated and
> > changed things around in a way that broke Hpodder; not surprising,
> > since HaXml-1.19.2 is as recent as 14 January
On Tue, 8 Apr 2008, Jackm139 wrote:
Thanks for all the replies!
I have it working somewhat. It works as long as there is only one string in
each list, but if the lists contain more than one string it fails. here is
what I have:
import List
same :: [[Char]] -> [[Char]] -> Bool
same [xs] [ys
> However, I have found two bugs, or annoyances:
> Using Opera 9.27 or Internet Explorer 7,
> - Search results vanish when using the "back" button
Yes, that is a known problem. Although I have no good idea how to solve this
while keeping the AJAX stuff (that is, find as you type).
> - the "Sourc
On 2 Apr 2008, at 16:20, Loup Vaillant wrote:
class AdditiveSemiMonoid a where
(+) :: a -> a -> a
Err, why *semi* monoid? Plain "monoid" would not be accurate?
I found an example where it is crucial that the monoid has a unit:
When given a monoid m, then one can also define an m-algebra, b
Hi,
Am Dienstag, den 08.04.2008, 11:51 -0700 schrieb Dan Weston:
> Paul Johnson wrote:
> > You can regard an "instance" declaration as an inference rule for the
> > type checker, with "=>" meaning "implies" (though I don't think its the
> > answer to your other question about names).
>
> "implie
Paul Johnson wrote:
You can regard an "instance" declaration as an inference rule for the
type checker, with "=>" meaning "implies" (though I don't think its the
answer to your other question about names).
"implies" might be a bad word, because the direction is backwards:
Eq a => Ord a
is cl
On Tue, Apr 8, 2008 at 10:24 AM, Jackm139 <[EMAIL PROTECTED]> wrote:
> import List
>
> same :: [[Char]] -> [[Char]] -> Bool
> same [xs] [ys] = map (normalize) [[xs]] == map (normalize) [[ys]]
>
> normalize :: [String] -> [String]
> normalize [xs] = [(sort (nub xs))]
>
Your pattern binding [xs
Hooray for the release of darcs-2!
Way to go, David!
Regards,
Zooko
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Hi, Bjorn and Uwe --
> > this is a known problem with HTTP package (version 3001.0.4).
> > Paul Brown has described this somewere in his blog.
> > (http://mult.ifario.us/t/haskell), but my firefox only shows
> > an incomplete page of this blog, the solution is missing.
> > Paul promissed
Thanks for all the replies!
I have it working somewhat. It works as long as there is only one string in
each list, but if the lists contain more than one string it fails. here is
what I have:
import List
same :: [[Char]] -> [[Char]] -> Bool
same [xs] [ys] = map (normalize) [[xs]] == map (norma
PR Stanley wrote:
Hi
What is the difference between
data T0 f a = MkT0 a
instance Eq (T0 f a) where ...
and
data T0 f a = MkT0 a
instance Eq a => Eq (T0 f a) where ...
The second one says that "TO f a" is only an instance of "Eq" if "a" is,
while the first says that "
Hi
What is the difference between
data T0 f a = MkT0 a
instance Eq (T0 f a) where ...
and
data T0 f a = MkT0 a
instance Eq a => Eq (T0 f a) where ...
I've only seen the "=>" operator used for declaring extended classes
but never with class insta
Neil Mitchell schrieb:
> Hi
>
>
>> You got it right. The issue is that in TagSoup.hs there is a line like
>> 'parseTagsOptions (options { foo =...}'. That's invalid syntax AFAIK;
>>
>
> It's just record syntax, which is very handy.
>
>
>> more importantly, it's using functions from ndm
On 8 Apr 2008, at 17:03, Christian Maeder wrote:
"deriving Eq" i.e. following "data List a = List a" creates an
instance
like:
instance Eq a => Eq (List a) where
The problem was discussed for Stand-alone deriving declarations:
http://www.haskell.org/ghc/docs/latest/html/users_guide/derivin
On 8 Apr 2008, at 16:57, Anton van Straaten wrote:
So what is the difference from the current state?
None. See how efficient a solution it is? ;)
So for a change, you propose it should be the same. So you are one of
those A-programmers :-).
Seriously, there's only so much connotational
Anton van Straaten wrote:
> How about making "deriving x" an expression which means:
>
> instance x where
"deriving Eq" i.e. following "data List a = List a" creates an instance
like:
instance Eq a => Eq (List a) where
The problem was discussed for Stand-alone deriving declarations:
http:
Hans Aberg wrote:
On 8 Apr 2008, at 16:32, Anton van Straaten wrote:
There are two processes here: deriving, i.e., inheriting an
interface; and instantiating, i.e., producing running code. Haskell
denotes derivation by "=>". And "data deriving (b_1, ..., b_k)"
is really a short for
data
On 8 Apr 2008, at 16:32, Anton van Straaten wrote:
There are two processes here: deriving, i.e., inheriting an
interface; and instantiating, i.e., producing running code.
Haskell denotes derivation by "=>". And "data deriving
(b_1, ..., b_k)" is really a short for
data
instance b_1 wh
David, thank you for the last push, and clear re-org! And thanks to all
darcs 2 contributors.
-Simon
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Hans Aberg wrote:
There are two processes here: deriving, i.e., inheriting an interface;
and instantiating, i.e., producing running code. Haskell denotes
derivation by "=>". And "data deriving (b_1, ..., b_k)" is really a
short for
data
instance b_1 where
...
instance b_k where
So
On Tue, Apr 8, 2008 at 4:46 AM, Paul Keir <[EMAIL PROTECTED]> wrote:
> I have noticed something interesting though. If I simply omit the "a"
> from "opLetter", the problem is gone. In fact, leaving "opStart",
> "opLetter", and "reservedOpNames" all empty works fine too.
That makes sense. opLet
On 8 Apr 2008, at 15:26, PR Stanley wrote:
I'm sure you could introduce change gradually without too much pain.
So then you only have to get the compilers to gradually understand
it :-).
I personally think "deriving" is a descriptive term, now that I
understand its role better.
There ar
You might find it helpful to read our new paper: Type checking with open type
functions http://research.microsoft.com/%7Esimonpj/papers/assoc-types/index.htm
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Hugo Pacheco
Sent: 07 April 2008 22:47
To: Haskell Cafe
Subject: [Haskell-
Hello Hans,
Tuesday, April 8, 2008, 12:17:38 PM, you wrote:
> "deriving" which I think is not used elsewhere. It will break a lot
> of code, but it is easy to change, and also easy to make a
> compatibility mode.
it's also easy to replace all the books, update all code repositories
and reteac
Hi, I've added some features to shim.
You can get my patches here:
http://mawercer.de/~publicrepos/shim/
The Vim interface now supports
:GrepScope regex
Which greps the whole scope of all used packages by regex.
Very useful to find all functions taking/ returning some type
Daniel McAllansmith wrote:
> I'm having some problems with connections leaking when using 7.4. I've
> just checked and it happens with 7.5 off of hackage as well.
>
> It appears that readDocument doesn't close the connection when using the
> haskell http library, it works ok when curl is used tho
ln wrote:
> I would like to try HXT, but I can't manage to build it. I resolved all
>
> the dependencies, but I get the following error:
> > > [EMAIL PROTECTED]:~/Desktop/hxt$ make all
> > > make -C src all VERSION=7.5
> > > make[1]: Entering directory `/home/ln/Desktop/hxt/src'
> > > make in
I am pleased to announce that a new issue of The Monad.Reader is now
available:
http://www.haskell.org/haskellwiki/The_Monad.Reader
Issue 10 consists of the following two articles:
* Bernie Pope
Step inside the GHCi debugger
* Matthew Naylor
Evaluating Haskell in Haskel
On Mon, Apr 07, 2008 at 10:22:25AM -0700, David Roundy wrote:
> Hello darcs users,
>
> I am pleased to announce the release of darcs 2.0.0! It's been a long time
> coming, and hopefully you will be pleased with the result. Notable new
> features include (in no particular order):
>
Hello,
Congr
2008/4/8, Manuel M T Chakravarty <[EMAIL PROTECTED]>:
> You need to write the instance as
>
> instance (b ~ TheFoo a, Foo a) => Bar (Either a b) where
> bar (Left a) = foo' a
> bar (Right b) = foo' (foo b :: a)
>
If you do that, the program compile, but res still raise a panic in GHC6.8
On 8 Apr 2008, at 10:47, Bulat Ziganshin wrote:
"deriving" which I think is not used elsewhere. It will break a lot
of code, but it is easy to change, and also easy to make a
compatibility mode.
it's also easy to replace all the books, update all code repositories
and reteach all the programmer
Using 'hugs -98', I noticed it accepts:
instance Monad m => Functor m where
fmap f x = x >>= return.f
Has this been considered (say) as a part of the upcoming Haskell Prime?
Hans Aberg
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ht
The point is that Mark proposes a *pessimistic* ambiguity check whereas
Tom (as well as GHC) favors
an *optimistic* ambiguity check.
By pessimistic I mean that we immediately reject a program/type if
there's a potential
unambiguity. For example,
class Foo a b
forall a b. Foo a b => b -> b
Hello Hans,
Tuesday, April 8, 2008, 12:17:38 PM, you wrote:
> "deriving" which I think is not used elsewhere. It will break a lot
> of code, but it is easy to change, and also easy to make a
> compatibility mode.
it's also easy to replace all the books, update all code repositories
and reteach
Thanks Chris,
When I looked at the Fortran alphaNum operators (.and. .or. etc.) I had
hoped that supplying Parsec's "opStart" with a dot would have been
hitting the nail on the head. Oh well.
I have noticed something interesting though. If I simply omit the "a"
from "opLetter", the problem is gon
On 8 Apr 2008, at 00:30, Bulat Ziganshin wrote:
At least Hugs complains if one does not indent "deriving ...", but I
do not know what the standard says. If is required, then it can be
changed.
deriving is a part of data clause and indentation just allows us to
continue clause from prev. line. i
"Galchin, Vasili" <[EMAIL PROTECTED]> writes:
> What are some examples of libraries in HackageDB that use either Quick
> Check (pure side) or Monad testing? Is there a way to use "darcs" to answer my
> question?
I used the ByteString library as a guideline when developing testing
(and to a
Hi
> You got it right. The issue is that in TagSoup.hs there is a line like
> 'parseTagsOptions (options { foo =...}'. That's invalid syntax AFAIK;
It's just record syntax, which is very handy.
> more importantly, it's using functions from ndm's TagSoup library. TagSoup,
> with version 0.5, r
Hi Tom,
It seems we are thinking of different things. I was referring to
the characterization of a type of the form P => t as being "ambiguous"
if there is a type variable in P that is not determined by the
variables in t; this condition is used in Haskell to establish
coherence (i.e., to show t
Hello,
What are some examples of libraries in HackageDB that use either Quick
Check (pure side) or Monad testing? Is there a way to use "darcs" to answer
my question?
Thanks, vasili
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Manuel Chakravarty wrote:
>Ganesh Sittampalam:
>> On Mon, 7 Apr 2008, Manuel M T Chakravarty wrote:
>>
>>> Ganesh Sittampalam:
The following program doesn't compile in latest GHC HEAD, although
it does if I remove the signature on foo'. Is this expected?
>>>
>>> Yes, unfortunately, this
Ganesh Sittampalam:
On Mon, 7 Apr 2008, Manuel M T Chakravarty wrote:
Ganesh Sittampalam:
The following program doesn't compile in latest GHC HEAD, although
it does if I remove the signature on foo'. Is this expected?
Yes, unfortunately, this is expected, although it is very
unintuitive.
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