Have a look at the wikibook:
http://en.wikibooks.org/wiki/Haskell/Simple_input_and_output
Am 07.05.2009 um 11:46 schrieb applebiz89:
I havent done much IO at all in haskell, only within the function
itself.
However I want to get the input from the interface for the function
and
havent
Hello,
I'm trying to prove the unfold fusion law, as given in the chapter
Origami Programming in The Fun of Programming. unfold is defined
like this:
unfold p f g b = if p b then [] else (f b):unfold p f g (g b)
And the law states:
unfold p f g . h = unfold p' f' g'
with
p' = p.h
I've just uploaded a package with some functions I had lying around.
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Numbers
Am 14.04.2009 um 14:40 schrieb Niemeijer, R.A.:
Today I happened to need a large list of prime numbers. Obviously
this is a well-known problem, so I
Am 21.03.2009 um 13:30 schrieb Michael Mossey:
Thomas Davie wrote:
On 21 Mar 2009, at 00:16, Michael P Mossey wrote:
Hello, I'm totally new to Haskell. I'm thinking of using it for a
personal project, which is a gui-based musical score editor.
The rough situation of GUI programming on
You should not rely on the compiler to spot such things. As far as I
know GHC doesn't do automatic caching (in many cases that would hurt
performance, I think). Have a look at http://haskell.org/haskellwiki/
Memoization perhaps.
Am 21.03.2009 um 14:02 schrieb Michael Mossey:
I understand
http://lmgtfy.com/?q=haskell+run+length+codingl=1
But you'll learn nothing if you just copy that
Am 19.03.2009 um 03:24 schrieb THANDO NTUANE:
- Forwarded Message
From: THANDO NTUANE thandodar...@yahoo.com
To: Haskell-Cafe@haskell.org
Sent: Thursday, March 19, 2009 10:22:40 AM
Use a nested list comprehension, for example
Prelude [['a'| i - [0..n]]++\n|n - [1..3]]
[aa\n,aaa\n,\n]
Am 18.03.2009 um 07:47 schrieb Melanie_Green:
What are the limitations of list comprehension. I want to use
listcomprehension to output the pattern below. So a mixture of a's and
` alpha)
And it works as long as oplus is strict in both arguments.
Am 10.03.2009 um 21:54 schrieb John Dorsey:
Adrian Neumann wrote:
Notice that there is no difference between
foldr g a
foldl f a
(for appropriate g and f) if g and f are strict in both arguments.
Be careful... as apfelmus noted
You can use the ghci debugger
http://www.haskell.org/ghc/docs/latest/html/users_guide/ghci-
debugger.html
it can set breakpoints on exceptions.
Am 14.03.2009 um 09:39 schrieb Colin Paul Adams:
I'm getting a runtime failure Error in array index. This causes ghci
to exit.
Is there a way
Read this excellent paper:
http://www.cs.nott.ac.uk/~gmh/fold.pdf
Am 11.03.2009 um 19:24 schrieb R J:
foldl and foldr are defined as follows:
foldr:: (a - b - b) - b - [a] - b
foldr f e [] = e
foldr f e (x : xs) = f x (foldr f e xs)
foldl
You could turn on -Wall to get a whole bunch of such warnings.
Am 01.03.2009 um 14:26 schrieb Nicu Ionita:
Hi,
Today I found the following problem when writing a simple function:
-- Whole info from a word8 list to moves
movesFromWord8s :: [Word8] - [Move]
movesFromWord8s (f:t:ws) = (f, t) :
Am 05.02.2009 um 09:10 schrieb Andrew Coppin:
And so, inspired by the marketing litrature, I just spent £££ on a
very expensive new GPU that supports CUDA. The only problem is... I
can't seem to get any software to use it.
Does anybody know how to make this stuff actually work?
(Also...
Hello,
it is my pleasure to announce the DecisionTree package. It provides
an implementation of the ID3 algorithm [1] and can be used to
classify data with discrete valued attributes.
You can get it from
* hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/
DecisionTree
There was a thread about that:
http://www.haskell.org/pipermail/haskell-cafe/2007-September/
031402.html
Am 20.01.2009 um 11:07 schrieb Jim Burton:
Hi, I will be a TA on a comparative PL course and I'm looking for
small examples (ammunition) which motivate the use of Haskell and
functional
You need some type constructor:
data Tree a = Leaf a | Branch (Tree a) (Tree a)
Am 01.01.2009 um 08:32 schrieb Max.cs:
hi all, I want to define a data type Tree a that can either be a
or Branch (Tree a) (Tree a)?
I tried
data Tree a = a | Branch (Tree a) (Tree a) deriving Show
but it
Better would be
[] = 0
['a'] = 1
['b'] = 2
...
['z'] = 26
['a','a'] = 27
['a','b'] = 28
(asuming Char = ['a'..'z'])
Am 30.12.2008 um 04:25 schrieb JustinGoguen:
I am having difficulty making [Char] an instance of Enum. fromEnum
is easy
enough: map fromEnum to each char in the string and
Hello Haskell-Cafe,
lately I've been playing around with sorting. I discovered that
Data.List.sort is not as optimized I thought. At least not for random
lists. I think we should consider adding a Data.List.Sort package to
hackage (Similar to Data.List.Split) that offers a wide variety of
schrieb Bayley, Alistair:
From: haskell-cafe-boun...@haskell.org
[mailto:haskell-cafe-boun...@haskell.org] On Behalf Of Adrian Neumann
I don't consider myself to be a very advanced Haskell
programmer, but
I could come up with a Mergesort that beats List.sort, time- and
spacewise.
http://hpaste.org
Am 23.12.2008 um 15:16 schrieb Hans van Thiel:
Hello All,
I just saw somewhere that one of the purposes of monads is to capture
side effects. I understand what a side effect is in C, for example.
Say
you want to switch the contents of two variables. Then you need a
third
temporary
Hi,
I have a strange problem with interact on OS X (ghc 6.10.1). It
seems to garble stdin.
I have some code here http://hpaste.org/13135#a2 , for testing purpose:
*Main main
1
1.0
2
1.5
3
2.0
*Main setNonBlockingFD: invalid argument (Bad file descriptor)
11:40:45 ~/Desktop
(I hit
Am 27.11.2008 um 09:23 schrieb Don Stewart:
allbery:
On 2008 Nov 26, at 16:58, Matthias Kilian wrote:
On Wed, Nov 26, 2008 at 09:35:01PM +, Andrew Coppin wrote:
It is a fork of the JHC compiler, which should be easier to
look up.
There is also Hugs, as you mentioned. In addition, you
Hugs has, afaik, a output reduction count option somewhere. At
least it had one the last time I used it.
- Adrian
Am 22.11.2008 um 06:22 schrieb kk08:
Thanks.
I heard that a Gofer compiler (a Haskell dialect) supports counting
the Beta
reductions.
Hence I thought GHC/Hugs would have a
Thank you for your work! I just glanced over it but I'll suggest it
to be linked to from the homepage of my university's functional
programming course.
However, thirteen pages can hardly be called cheatsheet. It's more
like a quick reference.
You could add [100,99..] infinite liste of
of the
line is equal.
Does this work with more than two colours? i.e. can I recursively
subdivide the halves into quarters with another cut?
Am 01.10.2008 um 15:33 schrieb Dominic Steinitz:
Adrian Neumann aneumann at inf.fu-berlin.de writes:
I often wonder how many cuts you need
I often wonder how many cuts you need to divide a steak in n pieces.
You can obviously get n pieces with (sqrt n) cuts by cutting a grid.
But I'm sure some smart mathematician thought of a (log n) way.
Adrian
Am 29.09.2008 um 21:43 schrieb Andrew Coppin:
The other day, I sat down to eat a
There is the State Monad which is build just for that kind of purpose, I
believe:
http://www.haskell.org/all_about_monads/html/statemonad.html
That would safe you from passing around the State
Jefferson Heard schrieb:
Working with HOpenGL and GLUT, I find myself approaching a common
problem
Hello,
I think it'd be nice if the compiler could warn me if there are any
exceptions which I'm not catching, similar to checked exceptions in
Java. Does anyone know of a possibility to do that in Haskell?
Adrian
PGP.sig
Description: Signierter Teil der Nachricht
Maybe your image isn't strict enough and the computations are forced
when the image gets written to disc?
Am 20.07.2008 um 14:13 schrieb Mitar:
Hi!
Profiling says that my program spends 18.4 % of time (that is around
three seconds) and 18.3 % of allocations in this function which is
saving
Hello,
while studying for a exam I came across this little pearl:
Y = (L L L L L L L L L L L L L L L L L L L L L L L L L L L L)
where
L = λabcdefghijklmnopqstuvwxyzr. (r (t h i s i s a f i x e d p o i n
t c o m b i n a t o r))
posted by Cale Gibbard to this list. Now I'm wondering how
I would assume -O0, that is, turning off all optimizations, should
make compilation faster
Adrian
Am 17.06.2008 um 14:19 schrieb Samuel Silva:
Hello
I'm using GHC to compile around 700K of Haskell Code generated by
HaXml.
How I compile this code.
My machine is Windows-XP(512MB RAM,
{- I downloaded the source and put my file in the same directory
You may need to adjust the imports -}
module Main where
import Picture
import Draw -- change xWin to 1000 and yWin to 700 for this to work
import EnableGUI -- I use a Mac
import SOE hiding (Region)
import qualified SOE as G
I screwed up the email, sorry about that. What I wanted to say was:
Hello,
as homework I was assigned to design and draw an image using the
SOE Graphics library [1]. In order to impress my classmates I decided
to draw a bush-like thingy using a Lindenmayer-System. It turns out
quite nice
I think you need to put liftIO in front of the IO actions you want to
do inside the CGI Monad. Like in this example
http://www.haskell.org/haskellwiki/
Practical_web_programming_in_Haskell#File_uploads
(Why did I need to use google to find that? The wiki search in awful.
Searching for
Isn't fast IO what ByteStrings where invented for?
Adrian
Tom Harper schrieb:
I'm trying to implement some file I/O where I can read in a file to an
array, but do so without having to know how much space I will need.
(Before you suggest it, lists are too slow/space consuming.) I was
thinking
Hello,
I was wondering how expensive appending something to a list really is.
Say I write
I'd say longList ++ [5] stays unevaluated until I consumed the whole
list and then appending should go in O(1). Similarly when concatenating
two lists.
Is that true, or am I missing something?
Yes
http://hpaste.org/6990
Am 14.04.2008 um 19:07 schrieb Adam Smyczek:
Is form based file upload supported in HTTP module (HTTP-3001.0.4)?
Adam
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
Is there any Haskell compiler for Windows CE on a XScale platform? I
googled around a bit and found references to a Hugs implementation but
couldn't find any place to download it.
I have the opportunity to program a teledrive[1] and would very much
like to avoid something disfunctional like
Hi,
I wrote a CGI program to access a Postgres database using HDBC. The
database stores books and I want to display those from a certain
author. Everything works fine, unless I search for someone with an
umlaut in his name. Böll, for example. I have a function like this
bookByAuthor ::
Hello Haskell-Cafe!
I've read about Control.Parallel and wanted to give it a try. Here's
what I wrote:
---
import Control.Parallel
import Data.List
splitList :: [Integer] - [[Integer]]
splitList = unfoldr f where
f [] = Nothing
f ~x = Just (splitAt 3 x)
map' :: (a-b) -
Hello haskell-cafe!
After making data Number = Zero | Succ Number an instance of
Integral, I wondered how I could do the same with galois fields. So
starting with Z mod p, I figured I'd need something like this
data GF = GF Integer Integer
so that each element of the finite field would
Good morning,
as an exercise for my Algorithms and Programming course I have to
program a couple of simple functions over trees. Until now everything
we did in Java could be done in Haskell (usually much nicer too)
using the naive
data Tree a = Leaf a | Node a [Tree a]
But now the
-BEGIN PGP SIGNED MESSAGE-
Hash: RIPEMD160
I heard only rumors, but isn't Lisp supposed to be just that? A
programmable programming language?
Peter Verswyvelen schrieb:
This is all very cool stuff, but sometimes I wander if it isn't possible
to drop the special languages for fiddling
-BEGIN PGP SIGNED MESSAGE-
Hash: RIPEMD160
I try to write a Windows Bitmap File using Data.Binary, but I have some
trouble.
For example, the internet states, that the magic number, that puts 'BM'
in the first two bytes of the file is 19778. But when I
put (19778::Word16)
I get 'MB'
-BEGIN PGP SIGNED MESSAGE-
Hash: RIPEMD160
I'm toying around with web programming in Haskell. I'm trying to write a
script which GETs an id and returns a couple of random numbers.
Something like this:
cgiMain :: CGI CGIResult
cgiMain = do
inp - getInput id
let gen = parse
-BEGIN PGP SIGNED MESSAGE-
Hash: RIPEMD160
Hi,
I wrote a brute-force sudoku solver. It takes a [[Int]] and spits out
the first solution it finds.
Why is it, that
[0,0,0,7,0,6,9,0,0]
[9,0,0,0,0,4,7,0,0]
[7,0,0,0,0,0,4,0,0]
[0,2,7,0,3,5,8,0,0]
[6,9,5,8,2,0,0,0,0]
[0,8,0,0,0,0,5,0,0]
-BEGIN PGP SIGNED MESSAGE-
Hash: RIPEMD160
Hi,
I installed the Network.CGI package and tried to compile the Hello World
example on my Ubuntu machine.
ghc cgi.hs -o cgi
gives me
cgi.o: In function `r1hk_info':
(.text+0x56): undefined reference to
-BEGIN PGP SIGNED MESSAGE-
Hash: RIPEMD160
Are there any good books about intermediate to advanced Haskell? The
descriptions here http://haskell.org/haskellwiki/Books_and_tutorials
aren't very helpful.
Adrian
-BEGIN PGP SIGNATURE-
Version: GnuPG v1.4.7 (MingW32)
Comment: Using
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA512
I've read this blogpost about the trivial monad
http://sigfpe.blogspot.com/2007/04/trivial-monad.html, because I still
don't understand what this monad thingy is all about.
The author defines three functions:
data W a = W a deriving Show
return
-BEGIN PGP SIGNED MESSAGE-
Hash: RIPEMD160
Hello,
I defined an enumeration datatype like this
data MyType = One | Two | Four | Eight
and want to make it an instance of the class Enum. deriving Enum won't
do what I want, as it labels the items 0,1,2,3. Is there a better way to
do this
49 matches
Mail list logo
