Hello cafe,
When I want to locally install my own package through cabal install it
tries to reinstall dependencies convertible-1.0.9.1, HDBC-2.2.6.1 and
HDBC-mysql-0.6.3 even though they are already installed (and work fine).
Why does it do this?
cabal-install version 0.8.2
using version
Dear cafe,
Following the instructions at
http://matt.freels.name/2010/hdbc-mysql-os-x.html I successfully
installed HDBC-mysql on my Mac!
However when doing a cabal install in a local package which depends on
HDBC-mysql, cabal proceeds to reinstall HDBC-mysql (is this a bug? see
my other
Hi Mark, Chris,
I had trouble as well but just found this pretty recent blog post by @freels
which worked like a charm for me:
http://matt.freels.name/2010/hdbc-mysql-os-x.html
I hope it works for you as well!
I've added Chris to the list of recipients because maybe he can incorporate
the fix
I have just booked 5 beds in Hostel 47 in Ghent for our group. We will
be staying in a 6-bed room, so there is still one bed available. If
anyone is still looking for a bed in Ghent and wants to share a room
with fellow Haskellers, that one bed might be an interesting choice. I
told them we
Are you saying that GHC complains about an unused import that is in fact
used? Perhaps you've run into this bug:
http://hackage.haskell.org/trac/ghc/ticket/1148
Are you using a recent version of GHC?
Groetjes,
Martijn.
On 8/10/10 22:22, Lyndon Maydwell wrote:
Hi Cafe.
I have written some
On 8/2/10 7:09, Ertugrul Soeylemez wrote:
Given the definition of a Haskell function, Haskell is a pure language.
The notion of a function in other languages is not:
int randomNumber();
The result of this function is an integer. You can't replace the
function call by its result without
On 8/10/10 23:27, Felipe Lessa wrote:
If we had in C:
return (randomNumber(10, 15) + randomNumber(10, 15))
That would not be the same as:
int x = randomNumber(10, 15)
return (x + x)
That's not fair. You're comparing C's '=' with Haskell's '='. But you
should be comparing C's '='
On 8/10/10 23:53, Felipe Lessa wrote:
and the result is IO Int. When we replace the function call by its
result, I think it is fair to replace the C function call by an int
and the Haskell function call by an IO Int, because that is what
those functions return.
Fair enough. :-)
Also, a
Dear café,
Given:
instance Category C
y :: forall r. C r (A - r)
I am looking for the types of x and z such that:
x . y :: forall r. C r r
y . z :: forall r. C r r
Can you help me find such types? I suspect only one of them exists.
Less importantly, at least to me at this moment: how do I
On 7/30/10 9:29, Stefan Holdermans wrote:
Jason,
There is one case where you can break out of a monad without knowing which
monad it is. Well, kind of. It's cheating in a way because it does force the
use of the Identity monad. Even if it's cheating, it's still very clever and
On 7/30/10 12:29, Tillmann Rendel wrote:
C K Kashyap wrote:
I am of the
understanding that once you into a monad, you cant get out of it?
That's not correct.
There are many monads, including Maybe, [], IO, ... All of these monads
provide operations (=), return and fail, and do notation
On 7/28/10 14:53, S. Doaitse Swierstra wrote:
see: file:///Users/doaitse/.cabal/share/doc/uu-parsinglib-2.4.2/html/index.html
Readers might have more luck with the following URLs:
http://hackage.haskell.org/package/uu-parsinglib
On 7/27/10 9:58, Sebastian Fischer wrote:
On Jul 27, 2010, at 9:15 AM, Sjoerd Visscher wrote:
Oh, by the way, with noMatch, eps, alt and seq_ RegExp is itself a
Semiring,
Yes, but it's hard to define an Eq instance for arbitrary regular
expressions that reflects equivalence of regexps.
On 7/21/10 12:48, José Romildo Malaquias wrote:
Hello.
I have noticed that I do not receive duplicate copies of messages from
haskell-cafe, although Avoid duplicate copies of messages? is set to
No in the mailing list membership configuration.
I want the copies because I archive all the
On 7/8/10 21:36, Stephen Tetley wrote:
Hello
I suspect you will have to choose single examples for each of the
patterns/ abstractions you are interested in.
Doaitse Swierstra's library UU.Parsing is the originator or the
Applicative style. Its latest incarnation is the library
uu-parsinglib.
On 6/14/10 10:39, Ivan Lazar Miljenovic wrote:
By being told that using them would solve some problem you're
complaining about on #haskell or the mailing lists, you look at
examples, read up on them, etc.
Short version: don't worry about advanced concepts until you have to.
If all else fails,
On 6/14/10 0:10, Roman Cheplyaka wrote:
Of course most parsers don't consume trailing newlines. But I was
writing general function to use in many places in the code which would
recover the end location. In most cases it just subtracts 1 from the
column number, but what if it just happened so
On 5/3/10 23:46, Jason Dagit wrote:
This happened to a co-worker on her mac. We used gdb to track the bus
errors to the network library. Once we tracked it down to there, we did
some combination of deleting $HOME/.cabal, building/installing the
latest version of Network and then relinking
Thanks! That's great news. Yes, all seems fine now. :-)
It was a very interesting bug to isolate. At one point I was in the
situation where compiling with -O2 fixed the problem and -O0 didn't,
seemingly consistently.
By the way, I got two warnings while compiling:
* Warning: Fields of
On 4/6/10 15:31, Heinrich Apfelmus wrote:
In fact, it doesn't actually work for monads, I think you have to wrap
it in a newtype. :D The same effect can be achieved with `ap` , though:
Fortunately, by now most (standard) monads are also applicatives. :-)
Besides generalizing to an arbitrary
Dear café (CC John and Chris),
I'm having some trouble with getting positional parameters in HDBC-mysql
to work. Most of the time they work fine, but sometimes (and often
enough that it's a serious bother) the parameters don't reach the server
correctly.
Let me first describe my setup:
*
+1 for lifting this restriction.
On 4/4/10 23:28, David House wrote:
An issue came up on #haskell recently with Hackage accounts requiring
real names.
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On 3/31/10 12:44, Heinrich Apfelmus wrote:
go Next (Single x t1) = liftM (Single x) (rewrite f t1)
go Next (Fork t1 t2 ) = liftM2 Fork (rewrite f t1)
(rewrite f t2)
In particular, liftM and liftM2 make it apparent that we're
Tom Schrijvers wrote:
data EvalDict sem = EvalDict { val :: Int - sem Int, add :: sem Int
- sem Int - sem Int }
An alternative option is to capture the structure in a GADT:
data Eval a where
Val :: Int - Eval Int
Add :: Eval Int - Eval Int - Eval Int
And then write what were instances
Ivan Miljenovic wrote:
On 16 February 2010 08:35, Don Stewart d...@galois.com wrote:
Enjoy the new decade of flexible, fusible, fast arrays for Haskell!
/me points out that 2010 is actually the last year of the decade, and
not the first year of a new decade...
There certainly is /a/ decade
Ryan Ingram wrote:
Unfortunately, this makes things like
infinite_xs - sequence (repeat arbitrary)
no longer work, since the state never comes out the other side.
You're asking to execute an infinite number of monadic actions. How can
this ever terminate at all?
Martijn.
Edward Kmett wrote:
Functional references let you both read and write 'attributes' in a
structure. These can be chained to access members of members.
You can also use them to build bidirectional views on fields (and
compose those again as well).
Martijn.
Antoine Latter wrote:
getResponse = do
require 256
x - getX
len - getWord16be
y - getY
z - getZ
require (fromIntegral len * 8)
a - getA
b - getB
return $ Response x y z a b c
This looks like code that could be written in applicative style, in
which case you could analyze the
Dear café,
I am deeply impressed with Vacuum[1][2], Ubigraph[3] and especially
their combination[4]. I can trivially and beautifully visualize the ASTs
that my parser produces. I can visualize zippers of the ASTs and confirm
that sharing is optimal.
Ubigraph is also able to animate graph
Niklas Broberg wrote:
Haskell '98 apparently features 25 reserved words. (Not counting forall
and mdo and so on, which AFAIK are not in Haskell '98.)
21 actually. case, class, data, default, deriving, do, else, if,
import, in, infix, infixl, infixr, instance, let, module, newtype, of,
then,
Günther Schmidt wrote:
Hi,
when I cabal-installed the iteratee package, the transformers package
was also installed as a dependency.
Now when I run applications that import Control.Monad.Transformers I get
this:
Could not find module `Control.Monad.Trans':
it was found in
Hello,
Above error is one of those that appear when using GHC on the 64-bit
Snow Leopard. I've already patched my /usr/bin/ghc to mention -optc-m32
-opta-m32 -optl-m32. However, the error still occurs when doing 'cabal
haddock' in *some* packages.
For example, a local project of mine builds
Gregory Collins wrote:
Martijn van Steenbergen mart...@van.steenbergen.nl writes:
Hello,
Above error is one of those that appear when using GHC on the 64-bit Snow
Leopard. I've already patched my /usr/bin/ghc to mention -optc-m32 -opta-m32
-optl-m32. However, the error still occurs when doing
Max Cantor wrote:
That stuffed me up for a bit. I wrote some ugly template haskell a while back
to automatically generate XmlPickler instances. can send to you if you want
I recall typLAB writing about generic XML picklers:
http://blog.typlab.com/2009/11/writing-a-generic-xml-pickler/
Radek Micek wrote:
Hi,
thank you for your reply but your MulExpr
does not support expressions like
(2*3)+5
Oh! You're right, how silly of me.
Martijn.
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Eugene Kirpichov wrote:
Hello.
Consider the type: (forall a . a) - String.
On one hand, it is rank-2 polymorphic, because it abstracts over a
rank-1 polymorphic type.
On the other hand, it is monomorphic because it isn't actually
quantified itself: in my intuitive view, a parametrically
Don Stewart wrote:
vandijk.roel:
On Wed, Dec 2, 2009 at 11:44 PM, Gregory Crosswhite
gcr...@phys.washington.edu wrote:
On a more serious note, Download Haskell /= Download Haskell Platform, so if I were glancing
down the sidebar looking for a link to download the Haskell Platform then the
Luke Palmer wrote:
On Fri, Dec 4, 2009 at 10:26 AM, Radek Micek radek.mi...@gmail.com wrote:
Hello.
I have two types for expression:
data Expr = Add Expr Expr | Mul Expr Expr | Const Int
data AExpr = AAdd AExpr AExpr | AConst Int
The first one supports addition and multiplication and the
Hi Radek,
Radek Micek wrote:
I can write a function to simplify the first expression:
simplify :: Expr - Expr
simplify = {- replaces:
a*1 and 1*a by a,
a+0 and 0+a by a -}
And I would like to use the function simplify for the second type
AExpr. What can I do is to convert AExpr to Expr,
So here's a totally wild idea Sjoerd and I came up with.
What if newtypes were unwrapped implicitly?
What advantages and disadvantages would it have?
In what cases would this lead to ambiguous code?
Thanks,
Martijn.
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Hello,
I have a type family and a type class:
type family ErrorAlg (f :: (* - *) - * - *) e ix :: *
class MkErrorAlg f where
mkErrorAlg :: ErrorAlg f e a - f (K0 a) ix - Either e a
Instances for these two really go hand in hand, so I thought I would
move the type family into the type
Sebastian Fischer wrote:
Does anyone know why types and values are in separate namespaces but
classes and types are not?
Good question. I don't know the answer, but it is interesting to note
that the report explicitly mentions this decision (but provides no reason):
An identifier must not
zaxis wrote:
then how to use `X` ? Would you mind explaining the newtype X in detail ?
You can just think of a newtype as a normal datatype:
data X a = X (ReaderT XConf (StateT XState IO) a)
I.e. construction and pattern matching work indentically.
Every newtype you will find will have
Hi Sean,
Sean Leather wrote:
Perhaps this isn't answering your question, but you can turn the above
into an associated type as follows.
class MkErrorAlg f where
type ErrorAlg (f :: (* - *) - * - *) :: * - * - *
mkErrorAlg :: ErrorAlg f e a - f (K0 a) ix - Either e a
That is
Simon Peyton-Jones wrote:
It used to be, because GHC used to implement so-called deep skolemisation.
See Section 4.6.2 of
http://research.microsoft.com/en-us/um/people/simonpj/papers/higher-rank/putting.pdf
Deep skolemisation was an unfortunate casualty of the push to add impredicative
Hello,
Are there currently any known problems that would hinder the
implementation of kind polymorphism [1], e.g. unresolved inelegancies or
technical limitations, or is it only a matter of finding the time to
implement it?
Thanks,
Martijn.
[1]
Tony Morris wrote:
I have two projects that I intend to put on hackage soon. One depends
on the other. I have cabaled both. I am wondering how others work
with this kind of set up where changes are made to both libraries as
they work.
You just update and re-upload the packages as necessary. It
Henning Thielemann wrote:
On Wed, 4 Nov 2009, Sjoerd Visscher wrote:
On Nov 4, 2009, at 3:21 PM, Twan van Laarhoven wrote:
I looked on hackage but I was surprised that I couldn't find
this simple
monad. The package level-monad does look very similar, only it
uses a
Louis Wasserman wrote:
+1 on Control.Monad.Omega. In point of fact, your diagN function is simply
diagN = runOmega . mapM Omega
You'll find it an interesting exercise to grok the source of
Control.Monad.Omega, obviously, but essentially, you're replacing
concatMap with a fair (diagonal)
Dear café,
I am looking for a function that does an N-dimensional diagonal
traversal. I want the traversal to be fair: the sum of the indices of
the produced combinations should be non-decreasing. Let me illustrate
with an example.
The type of a 2-dimensional traversal would look like this:
Magnus Therning wrote:
IIRC James Gosling once said that if he were to design Java today he would
leave out classes. I suppose partly due to many of the issues with data
inheritance.
This sounds interesting. Can you link us to an article, please?
Thanks,
Martijn.
Yusaku Hashimoto wrote:
Hello cafe,
Do you know any data-type which is Applicative but not Monad?
The Except datatype defined in the Applicative paper.
Some parsers are not monads, allowing for optimizations.
Martijn.
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Hi Ozgur,
Ozgur Akgun wrote:
pKeyword_Int = ( \ _ _ _ - int ) $ pSym 'i' * pSym 'n' * pSym 't'
pKeyword_Float = ( \ _ _ _ _ _ - float ) $ pSym 'f' * pSym 'l'
* pSym 'o' * pSym 'a' * pSym 't'
As you can see there is an obvious pattern if you try to capture a
keyword. If there were a function
Hello!
I'm happy to announce the first release of HoleyMonoid, a datatype that
helps you build monoids with holes in them. The holes are filled in
later using normal function application. For example:
let holey = now x =
. later show
. now , y =
.
Anton van Straaten wrote:
On the plus side, this does make for a slogan with high market appeal:
Haskell: Kittens inside
Thanks. Now I have trouble getting this image of lambda-shaped bonsai
kittens out of my head.
;-)
Martijn.
___
Thanks for all the pointers, guys. You've been very helpful.
I also found Type-indexed data types (Hinze et al) to be a good source.
Much appreciated!
Martijn.
Martijn van Steenbergen wrote:
data ExprF r
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Haskell
Niklas Broberg wrote:
Actually, it seems something went awry. I got a 500 Internal Server
Error on my cabal upload, the package is there on hackage but it seems
it was never added to the list of packages. This means cabal update
doesn't know about it, nor is it listed on the What's New page.
Bonjour café,
data ExprF r
= Add r r
| Sub r r
| Mul r r
| Div r r
| Num Int
This is a well-known pattern that for example allows nice notation of
morphisms. But what is it called? I've heard fixed-point view, open
datatypes and some others, but I'm curious where
Waldemar Biernacki wrote:
Is there the eval function like in imperative languages?
You mean like in interpreted languages?
I'd like to write an application which has to be compiled to exec file. It is
neccessary to performe some additional procedures which are unknown at the
moment of the
Peter Verswyvelen wrote:
For learning, I would like to develop my own implementation of type
inference, based on the paper Typing Haskell in Haskell.
At first sight, the source code of THIH contains a small number of
tests, but I was wandering if a large test set exist?
I'm pretty sure GHC
David Virebayre wrote:
Taking the opportunity to thank very much both Simons and Ian for the
work they do and the enthusiasm they show. You guys rock.
I heartily second that!
Martijn.
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Dear café,
{-# LANGUAGE Rank2Types #-}
{-# LANGUAGE ImpredicativeTypes #-}
type Void = forall a. a
newtype Mono a = Mono { runMono :: [Void] }
beep :: Mono a - Mono a
beep (Mono vs) = Mono (map undefined vs)
Compiling this with GHC results in:
Monotype.hs:9:28:
Cannot match a
Hello café,
I've never written an Alternative instance for a newtype yet that
doesn't look like this:
instance Alternative T where
empty = T empty
T x | T y = T (x | y)
Why does newtype deriving not work for Alternative? (It works fine for
Monoid.)
Thanks,
Martijn.
You guys are right. I was being silly. Thanks. :-)
Ryan Ingram wrote:
Works for me on GHC6.10.4:
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It doesn't work for this one:
newtype Split a = Split { runSplit :: [Either a (Char, Split a) ]}
But my handwritten instance remains identical.
Groetjes,
Martijn.
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Brandon S. Allbery KF8NH wrote:
My fix would be to have myPrefixOf require the prefix be terminated in
whatever way is appropriate (end of input, white space, operator?)
instead of simply accepting as soon as it gets a prefix match regardless
of what follows.
Maybe you can use notFollowedBy
Erik de Castro Lopo wrote:
However after reading the hackage descriptions of both Transformers and
MTL, it seems that they share a very similar heritage. I therefore hacked
the iteratee.cabal file and replaced the build-depends on transformers
with one on mtl and the package built quite happily.
Daryoush Mehrtash wrote:
I am trying to learn more about concurrent applications in Haskell by
studying an existing a real application source code. I would very much
appreciate if you can recommend an application that you feel has done a
good job in implementing a real time application in
Hallo café,
Can anyone think of datatypes that are Foldable but not Traversable?
If not, what is the purpose of having a separate Foldable class?
Thanks,
Martijn.
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Ross Paterson wrote:
On Fri, Oct 09, 2009 at 04:41:05PM +0200, Martijn van Steenbergen wrote:
Can anyone think of datatypes that are Foldable but not Traversable?
Set
Nice! Thank you all for your answers.
Martijn.
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Felipe Lessa wrote:
which unfortunately needs {-# LANGUAGE RecursiveDo #-} or
some ugliness from mfix
But mdo/mfix is awesome! :-(
Martijn.
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minh thu wrote:
Also, I'd like to know why
id id True
is permitted but not
(\f - f f True) id
Because this requires rank-2 types:
Prelude :set -XScopedTypeVariables
Prelude :set -XRank2Types
Prelude (\(f :: forall a. a - a) - f f True) id
True
HTH,
Martijn.
Bas van Dijk wrote:
Comments and patches are highly welcome.
I tried to install on my Mac but bindings-common choked on:
cabal install bindings-common
Resolving dependencies...
cabal: Error: some packages failed to install:
bindings-common-1.1 failed while unpacking the package. The
Roel van Dijk wrote:
Yes, that happens. I don't now the cause but the work-around is easy.
Simply download the package manually from hackage, unpack and install
using cabal.
At least the following packages suffer from this problem:
bindings-common
bindings-libusb
bindings-posix
Perhaps
wren ng thornton wrote:
Another nice
thing this suggests is the ability to use underscore as a pattern for
when you know the compiler will infer the type but it's too complex to
want to write out (e.g. while experimenting).
I'd love this!
M.
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Bulat Ziganshin wrote:
in case you not seen this and may be interested:
http://okmij.org/ftp/Haskell/types.html#partial-sigs
Yes, I know there are workarounds (and I use them sometimes). It'd be
nice if there was direct support for them. :-)
Thanks,
Martijn.
Hi Michael,
Michael Shulman wrote:
Is there a way to make it automatically update a single contents page
with links to the documentation of all installed packages?
See:
http://thread.gmane.org/gmane.comp.lang.haskell.cafe/53531/focus=53560
David Menendez wrote:
I'm reminded of the parameterized monad of continuations that Oleg
mentioned a few years back.
http://www.haskell.org/pipermail/haskell/2007-December/020034.html
This is all very interesting, thank you both for the pointers!
I was trying to get rid of the newtypes but
Hello cafe,
Inspired by Sean Leather's xformat package [1] I built a datatype with
which you can build a monoid with holes, yielding a function type to
fill in these holes, continuation-passing style. Here are some
primitives and their types:
now :: m - ContSt m r r
later :: (a - m) -
brian wrote:
yep I had some trouble too, although interestingly less than on linux pc.
can you provide some error messages and we can see if your problems are
the same one's I saw.
If this helps, here is the error message I got:
Configuring hmatrix-0.5.2.2...
Checking foreign libraries...
You can use the error function. It accepts a string that is displayed
when the error is evaluated:
GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer ... linking ... done.
Loading package base ... linking ...
Hi Serge,
Serge LE HUITOUZE wrote:
I'm asking some advice on a small piece of code representing a
simplified version of a treatment I need to perform.
I have a line-oriented string/file, from which I want to extract
only a substring of those lines starting with char '+' (the detail
of the
Job Vranish wrote:
A simple but powerful implementation of function lenses (aka functional
references, accessors, etc..).
Nice! I will definitely give it a whirl when I pick up my MUD again. I'm
currently using accessors there. I see your functions are limited to use
in the state
Hi Colin,
Colin Adams wrote:
I'm trying to add a state monad onto the IO monad for use in a
happstack application. I thought this should involve using StateT and
Happstack.Server.SimpleHTTP.simpleHTTP', but I can't figure out how to
plumb it all together. Any tips will be welcome.
I'm not
Jason Dusek wrote:
Say we have a nice thread on this and we all realize that the
precedence of `do` and `case` could be changed (and changing
`if` would be nice but we can't have everything). How many
months/years would it take for any change in that direction to
occur?
Seven!
Right. How about:
f = map ((`div` 3) . sum . take 3) . tails
You probably want to do filter out some of the tails. Not sure where
transpose comes into play, but tails is your friend here.
Martijn.
Miguel Mitrofanov wrote:
transpose tails, I guess.
Jeremy Shaw wrote:
What I would prefer is:
instance (Monad f, Applicative f) = Applicative (ReaderT r f) where
pure a = ReaderT $ const (pure a)
f * a = ReaderT $ \r -
((runReaderT f r) * (runReaderT a r))
Right. This doesn't only go for ReaderT, it already goes for
David Menendez wrote:
data SomeNat where SomeNat :: (Nat n) = n - SomeNat
toPeano :: Int - SomeNat
or, equivalently, by using a higher-order function.
toPeano :: Int - (forall n. Nat n = n - t) - t
Nice! I thought the only way to create them was with a new datatype,
but this
Thanks for your replies.
Job Vranish wrote:
Martijn, how did you encounter this problem?
My list of input symbols contains some extra information and I was using
lookahead to query for that information before doing the actual parsing.
I was using it in various places, including a list of
Goedemiddag café,
Consider the following function, using parsec-3.0.0:
la :: Parsec String () (Maybe Char)
la = lookAhead (optionMaybe anyChar)
*Lookahead parseTest (char 'a' | char 'b') a
'a'
*Lookahead parseTest (char 'a' | char 'b') b
'b'
*Lookahead parseTest (la * char 'a' | char 'b') a
Sven Panne wrote:
and simply pass the unknown button numbers via this case. I am not so sure
about a nice name for this constructor: AdditionalButton? GenericButton? Or
simply MouseButton, just like the type itself?
How about OtherButton?
Martijn.
I suggest you all add your name and vote here:
http://doodle.com/4yrfd7qaw5man3rm
Perhaps we'll find one of the options is clearly in favor.
Martijn.
Bryan O'Sullivan wrote:
I've thought for a while that it would be very nice indeed if the Monoid
class had a more concise operator for
Ross Paterson wrote:
Generalizing (++) will break some Haskell 98 code, e.g.
append = (++)
I think that's a show-stopper.
Is the monomorphism restriction the only situation in which stuff breaks?
Martijn.
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Thomas Schilling wrote:
Haddock should allow documentation on instance
declarations...
+1!
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Tony Morris wrote:
Is there a canonical function for traversing the spine of a list?
I could use e.g. (seq . length) but this feels dirty, so I have foldl'
(const . const $ ()) () which still doesn't feel right. What's the
typical means of doing this?
(seq . length) doesn't sound that bad to
Jochem Berndsen wrote:
My default is to start developing, then adding -Wall -Werror and make it
compile again.
That and hlint!
Martijn.
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Hi Michael,
michael rice wrote:
as opposed to an inferred type?
Can you deduce from the following example?
Prelude let foo = () :: Int
interactive:1:10:
Couldn't match expected type `Int' against inferred type `()'
In the expression: () :: Int
In the definition of `foo': foo =
Richard Silverman wrote:
I'm puzzled by something. Suppose I have some code that does lots of IO,
and also occasionally refers to some global state. No problem, use
ReaderT for the state, combining with the IO monad. Except... since IO
is on the bottom, simple uses of do-notation such as foo -
Magicloud Magiclouds wrote:
61 threadDelay 1 -- ten seconds, but it just refresh crazy!
That's because threadDelay expects microseconds, not milliseconds. Try
multiplying your delay by 1000.
HTH,
Martijn.
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Benjamin L.Russell wrote:
image of new Haskell logo
image of Amtrak logo
ouch
The two logos do look disturbingly similar
This is nothing new. From [1]:
Amtrak changed their logo in 2000; the old logo looked like =.
Martijn.
[1]
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