On Fri, Jun 5, 2009 at 4:45 AM, wren ng thornton w...@freegeek.org wrote:
Johan Tibell wrote:
Could you be so kind to give an example for each?
In OOP you mean?
This cleared things up for me. Thanks!
-- Johan
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Evan Klitzke wrote:
I'm writing code with hslogger, and I'm finding myself frequently
writing things like this:
infoM $ printf %s saw %s with %s (show x) (show y) (show z)
Indeed writing these `show' is tedious. Fortunately, we can get rid of
them, still remaining in Haskell98. The
Hello Eric,
Friday, June 5, 2009, 12:17:42 AM, you wrote:
I'm using ghc 6.10.2 on Win XP. Are there any known solutions for this
problem?
Your question has inspired me to add a System.Environment.UTF8 module
to utf8-string 0.3.5
This module behaves like the System.IO.UTF8 wrapper.
it is
o...@okmij.org wrote:
Still, the code is a bit unsatisfactory because of the appearances of
error in pr_aux functions. The errors like passing too many or too
few arguments to printf (as demanded by the format specification) are
caught only at run-time. We can certainly do better.
I'd love
Bartosz Wójcik bar...@sudety.it writes:
myConcat' :: (Integral a) = Integer - [a] - [Integer]
:
myConcat' acc (x:xs) = case x `mod` 16 of
:
10 - fail $ show acc
11 - fail $ show acc
14 - fail $ show acc
Hi all,
I have some sample code:
full = do
let myOrder = initOrder
{ item = Just initItem
{ itemId = Something
}
, operation = Just Buy
}
putStrLn $ show myOrder
return ()
This is just a test project,
Hello,
Suppose I have two projects: 1) one that defines a monad transformer and
an accompanying type class that captures my monad-specific operations
and 2) one that uses the other project, combining the monad transformer
with, say, Parsec.
Now while writing my Parsec parser I want to use
Günther Schmidt gue.schm...@web.de writes:
I need a data structure as in my example without the [] being possible
to be empty.
Well, a list can by definition be empty, so this is clearly
impossible. The best you can do is to hide the constructors and have
smart constructor functions that
Hi John,
John Ky wrote:
full = do
let myOrder = init -- [1]
{ item = Just init
{ itemId = Something
}
, operation = Just Buy
}
putStrLn $ show myOrder
return ()
Where initOrder and initItem
From what I understand, the current best practices are to build your
package dependencies like so:
ParsecMyMonadT
MyMonadT_Parsec -- orphan instances go here
ProjectPackage
This does mean splitting up your project into three packages, but
decouples the orphan instance into its own
Hi,
it's alomost the same problem when you're writing a library with
optional quickcheck test cases: Where to put the Arbitrary instances?
- You can't put them into quickcheck
- You don't want to put them in the library (because of the quickcheck
dependency)
- So you have to declare them
Thomas ten Cate wrote:
Possible, yes.
Efficient, not really.
inTwain = foldr (\x (ls, rs) - if length ls == length rs then (x:ls, rs) else
(x:(init ls), (last ls):rs)) ([], [])
But this uses length and init and last all of which are recursive
functions. I consider that cheating: only
From what I understand, the current best practices are to build your
package dependencies like so:
ParsecMyMonadT
MyMonadT_Parsec -- orphan instances go here
ProjectPackage
This does mean splitting up your project into three packages, but
decouples the orphan instance into its own package
Geoffrey Marchant wrote:
The linked paper appears to show the right style.
This appears to satisfy the conditions, however:
inTwain as = let (x,y,_) = foldr (\a (r,s,t) - case (t) of {b:(b':bs)
- (r,a:s,bs); _ - (a:r,s,t)}) ([],[],as) as in (x,y)
This one is very interesting. Thanks. :-) It
Martijn van Steenbergen mart...@van.steenbergen.nl writes:
inTwain = foldr (\x (ls, rs) - if length ls == length rs then (x:ls, rs)
else (x:(init ls), (last ls):rs)) ([], [])
But this uses length and init and last all of which are recursive
functions. I consider that cheating: only foldr
Martijn van Steenbergen mart...@van.steenbergen.nl writes:
inTwain as = let (x,y,_) = foldr (\a (r,s,t) - case (t) of
{b:(b':bs) - (r,a:s,bs); _ - (a:r,s,t)}) ([],[],as) as in (x,y)
This one is very interesting.
Yes, neat.
I'm not too happy with the whole list as part of the initial
module IOStream where
import System.IO
import System.IO.Unsafe
class Out a where
out :: a → String
instance Show a ⇒ Out a where
out = show
instance Out String where
{-# SPECIALISE out :: String → String #-}
out = id
instance Out Char where
{-# SPECIALISE out :: Char → String #-}
On Fri, Jun 5, 2009 at 7:25 AM, Claus Reinke claus.rei...@talk21.com wrote:
If ProjectPackage actually depends on the existence of those orphan
instances, plan B is to delay instance resolution, from library to clients,
so instead of importing the orphan instances
module ProjectPackage where
Do you really need a class? Maybe, a simple data type would do?
So, instead of
class MyMonad m where
myVal1 :: m a
myVal2 :: m a - m [a]
instance Monad m = MyMonad (MyMonadT m) where
myVal1 = foo
myVal2 = bar
you can write (in your first package) something like
data MyMonad m
Miguel Mitrofanov wrote on 05.06.2009 16:53:
myMonadT :: Monad m = MyMonad m
Sorry, I've meant
myMonadT :: Monad m = MyMonad (MyMonadT m)
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| bar :: (C T) = T
| *Main :t bar
|
| interactive:1:0:
| No instance for (C T)
| arising from a use of `bar' at interactive:1:0-2
| Possible fix: add an instance declaration for (C T)
| In the expression: bar
I'm not sure where that comes from, but it does seem to be an
Now there's also a stackoverflow question for this:
http://stackoverflow.com/questions/955711/specialization-in-type-classes-using-ghc
Any help highly appreciated!
2009/6/5 Cetin Sert cetin.s...@gmail.com
module IOStream where
import System.IO
import System.IO.Unsafe
class Out a where
Martijn van Steenbergen mart...@van.steenbergen.nl wrote:
But this uses length and init and last all of which are recursive
functions. I consider that cheating: only foldr may do the recursion.
I think the key is to pick your intermediate data-structure wisely. A
pair of queues would be my
Hi folks
data NE x = x : Maybe (NE x)
?
It's Applicative in at least four different
ways. Can anyone find more?
Conor
On 5 Jun 2009, at 01:34, Edward Kmett wrote:
Günther,
Miguel had the easiest suggestion to get right:
Your goal is to avoid the redundant encoding of a list of one
Comrades
I'm in a perplexing situation and I'd like to appeal to the
sages.
I've never written anything other than static HTML in my life,
and I'd like to make a wee web service: I've heard some
abbreviations, but I don't really know what they mean.
I've got a function (possibly the identity,
On Fri, Jun 5, 2009 at 5:18 PM, Conor McBrideco...@strictlypositive.org wrote:
Will I need to ask systems support to let me install some
haskelly sort of web server? Looks likely, I suppose.
In general, what's an easy way to put a web front end on
functionality implemented in Haskell?
For
On Fri, Jun 5, 2009 at 8:18 AM, Conor McBride co...@strictlypositive.orgwrote:
Comrades
I'm in a perplexing situation and I'd like to appeal to the
sages.
I've never written anything other than static HTML in my life,
and I'd like to make a wee web service: I've heard some
abbreviations,
I bet they have PHP on the server already. Write your program so it
takes input from standard in and writes to standard out. Then just
run your executable from PHP and write to its pipe. Instant web
service!
On Fri, Jun 5, 2009 at 8:18 AM, Conor McBrideco...@strictlypositive.org wrote:
Comrades
The SPECIALIZE pragma doesn't do what you think; those implementations
are already as specialized as they get.
You can enable OverlappingInstances, but the big problem is that it
doesn't really work; consider this function:
foo :: Show a = a - String
foo x = out x
question = foo hello
What
Hello,
The following is a fragment in my cabal file:
Executable GraphPartitionTest
Main-Is:Swish.HaskellRDF.GraphPartitionTest.hs
Other-modules: Swish.HaskellRDF.GraphPartition
Swish.HaskellRDF.GraphClass
On Fri, 2009-06-05 at 16:18 +0100, Conor McBride wrote:
I've got a function (possibly the identity, possibly const ,
who knows?)
assistant :: String - String
and I want to make a webpage with an edit box and a submit
button. If I press the submit button with the edit box
containing
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA512
On Fri, Jun 5, 2009 at 3:33 PM, Vasili I. Galchin wrote:
Hello,
The following is a fragment in my cabal file:
Executable GraphPartitionTest
Main-Is:Swish.HaskellRDF.GraphPartitionTest.hs
Other-modules:
Packed Decimal downloaded on pc is just a stream of bytes without any comma. I
was supposed to reformat data. If I undersdand bytestring-csv library, it
parses csv format data.
Thanks for the hint. I'll investigate next time when I have to deal with huge
files.
Bartek
On Thursday 04 June 2009
Integer was on purpose. One of the fields was 14 digits number.
Usually I parse EBCDIC directly on mainframe. This time it was exception.
Bartek
On Thursday 04 June 2009 22:38:53 Michael Snoyman wrote:
I *do* know what Packed Decimal is; at my previous job, I actually had a
whole Haskell
Hi,
please write to the whole list, not just me. There are a lot of people
around who can help you.
MH wrote:
Rendel do you mind to explain to me how Container a = Many a
(Container [a]) prevents user from creating an empty list?
I did try the following:
let a = Many string
a :: Container
for directory structure I Swish-0.2.1/Swish/HaskellRDF and
Swish-0.2.1/Swish/HaskellUtils ... there are deeper directories but that
distract from the discussion ... to make things concete:
1) swish.cabal is directly under Swish-0.2.1
2) GraphPartitionTest.hs is under
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA512
On Fri, Jun 5, 2009 at 4:10 PM, Vasili I. Galchin wrote:
for directory structure I Swish-0.2.1/Swish/HaskellRDF and
Swish-0.2.1/Swish/HaskellUtils ... there are deeper directories but that
distract from the discussion ... to make things concete:
At work I am using Windose ... so I use runhaskell .. I don't have build
Vasili
On Fri, Jun 5, 2009 at 3:28 PM, Gwern Branwen gwe...@gmail.com wrote:
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA512
On Fri, Jun 5, 2009 at 4:10 PM, Vasili I. Galchin wrote:
for directory structure I
getting farther .
Executable GraphPartitionTest
Hs-source-dirs: Swish/ added this
Main-Is:HaskellRDF/GraphPartitionTest.hschanged to a real
filesystem path
Other-modules: HaskellRDF.GraphPartition
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA512
On Fri, Jun 5, 2009 at 4:49 PM, Vasili I. Galchin wrote:
getting farther .
Executable GraphPartitionTest
Hs-source-dirs: Swish/ Main-Is:
HaskellRDF/GraphPartitionTest.hsfilesystem path
If your module statements say Swish in them, e.g.
module Swish.HaskellUtils.TestHelpers where
then you should probably have no hs-source-dirs (or hs-source-dirs: .)
and then use Swish.HaskellUtils.TestHelpers.
But leave Main-Is: as you have it.
-Ross
On Jun 5, 2009, at 4:49 PM,
{-# LANGUAGE TypeFamilies #-}
module PeanoArith
data Z = Z
data S n = S n
So, this type family works just fine:
type family Plus a b
type instance Plus Z b = b
type instance Plus (S a) b = S (Plus a b)
As does this one:
type family Minus a b
type instance Minus a Z = Z
type instance
On Fri, Jun 05, 2009 at 01:58:33PM -0700, Ryan Ingram wrote:
I tried several different implementations for Times but I was unable
to come up with one that passed the type family termination checker.
Is there a way to do so?
Here is a solution. I don't understand exactly why this works while
Hi Conor,
As someone pointed out, CGI is one way to go.
Another option is to write a small Haskell web server. This path is
better if you have an app that needs to keep state, ans uses the
browser mostly as a GUI.
I have just made a package that should make doing this fairly easy. I
have not
This is a bit beyond my normal level of expertise, but if I understand
it correctly the type checker is normally limited to type functions that
are primitive recursive
(http://en.wikipedia.org/wiki/Primitive_recursive_function). This means
that they are guaranteed to terminate, but on the
I actually meant
data Container a = Many a(Container a)
but here is what I don't understand (fyi, I am a beginner) how can you
construct this container? I can do
let a = Many somestring - and I will get back a function but I can not do
let a = Many 'a' somestring - because the second param is
MH mha...@gmail.com writes:
data Container a = Many a(Container a)
but here is what I don't understand (fyi, I am a beginner) how can you
construct this container? I can do
let a = Many somestring - and I will get back a function but I can not do
let a = Many 'a' somestring - because the
On Fri, Jun 5, 2009 at 2:58 PM, MH mha...@gmail.com wrote:
I actually meant
data Container a = Many a(Container a)
but here is what I don't understand (fyi, I am a beginner) how can you
construct this container? I can do
I think I saw the above definition described as a coalgebra or
On Fri, Jun 5, 2009 at 4:13 PM, Jason Dagit da...@codersbase.com wrote:
On Fri, Jun 5, 2009 at 2:58 PM, MH mha...@gmail.com wrote:
I actually meant
data Container a = Many a(Container a)
but here is what I don't understand (fyi, I am a beginner) how can you
construct this container? I
Martijn van Steenbergen wrote:
Hello,
Suppose I have two projects: 1) one that defines a monad transformer and
an accompanying type class that captures my monad-specific operations
and 2) one that uses the other project, combining the monad transformer
with, say, Parsec.
Now while writing
I just watched http://video.google.com/videoplay?docid=810232012617965344
It's a great talk that is suprisingly relevant to Haskell programming
(although at first blush it looks a bit unrelated). (It refs a lot of
older work that actually led me to Haskell in the first place by way of
On Fri, Jun 5, 2009 at 6:38 PM, wren ng thorntonw...@freegeek.org wrote:
4) Define a newtype of MyMonadT Parsec and declare instances of MyMonad and
Parsec for it.
Yes, I know Parsec is (an alias for) a data type, not a type class. But for
the general problem, using newtype wrappers is
Tim Newsham news...@lava.net wrote in article
pine.bsi.4.64.0906051510070.14...@malasada.lava.net in
gmane.comp.lang.haskell.cafe:
his language also
supports an interesting imperative primitive that lets you pick the first
available value from a set of channels which isn't available in pure
Hi all,
Malcom Wallace wrote:
Martijn van Steenbergen mart...@van.steenbergen.nl wrote:
But this uses length and init and last all of which are recursive
functions. I consider that cheating: only foldr may do the recursion.
I think the key is to pick your intermediate data-structure
Tim Newsham news...@lava.net wrote in article
pine.bsi.4.64.0906051510070.14...@malasada.lava.net in gmane.comp.lang.haskell.cafe:
his language also
supports an interesting imperative primitive that lets you pick the first
available value from a set of channels which isn't available in pure
Hi all,
I'm trying to compile the binary-strict module from hackage and I'm
getting the exact same error as in the hackage build log:
http://hackage.haskell.org/packages/archive/binary-strict/0.4.2/logs/failure/ghc-6.10
src/Data/Binary/Strict/IncrementalGet.hs:106:11:
parse error on
On Fri, Jun 5, 2009 at 8:14 PM, Tim Newsham news...@lava.net wrote:
I just watched http://video.google.com/videoplay?docid=810232012617965344
It's a great talk that is suprisingly relevant to Haskell programming
(although at first blush it looks a bit unrelated). (It refs a lot of older
work
According to the Report:
nubBy:: (a - a - Bool) - [a] - [a]
nubBy eq [] = []
nubBy eq (x:xs) = x : nubBy eq (filter (\y - not (eq x y)) xs)
Hence, we should have that
nubBy () (1:2:[])
= 1 : nubBy () (filter (\y - not (1 y)) (2:[]))
= 1 : nubBy () []
= 1 : []
However
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