[Haskell-cafe] Beginner SOS
Dear anyone,I wish to learn HASKELL. However my institution does not teach it so plus I don't have a clue how to get around with it. Everything seems so unconventional and out of place Can you help me out in getting good tutorials that will help me to learn HASKELL by myself so that I can pursue it as a serious programming languages Till now I have referred Haskell wiki and have tried everywhere but does not seem to learn it PLZ, PLZ HELP ME OUT -- Regards MANU ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Problem building hdbc-sqlite3 with ghc 6.8.2
hello, has anybody managed to build hdbc-sqlite3 with ghc 6.8.2 ? I get the following error : Macintosh:HDBC-sqlite3-1.1.3.0 manu$ runhaskell Setup.lhs build Preprocessing library HDBC-sqlite3-1.1.3.0... ghc-6.8.2: unrecognised flags: -F/Users/manu/Library/Frameworks Usage: For basic information, try the `--help' option. compiling dist/build/Database/HDBC/Sqlite3/Statement_hsc_make.c failed command was: /usr/local/bin/ghc -c -package base-3.0.1.0 -package mtl-1.1.0.0 -package HDBC-1.1.3 -I. -F/Users/manu/Library/Frameworks dist/build/Database/HDBC/Sqlite3/Statement_hsc_make.c -o dist/build/ Database/HDBC/Sqlite3/Statement_hsc_make.o if somebody has an idea... Thanks E.D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell and DB : giving up
On Nov 29, 2007, at 10:49 AM, Ketil Malde wrote: I think this is the problem, not the solution. There is a lot of DB libraries, just like there are a multitude of XML libraries, several collections, etc. Too many libraries are written as research projects or by grad students, and left to rot after release. The fragmentation also means that few libraries see any extensive testing - I was a bit surprised that apparently none of the XML libraries can handle files larger than a few megabytes, for instance. Hello My post wasn't intended as raging criticism, I can guess that developping these libraries takes a lot of (unpaid) work. And I am grateful for these libraries no matter what. However, if what is needed to install and use MySQL (or another popular DB) from Haskell could be drastically made shorter and easier, more people might use Haskell in domains where it still is largely marginal (like say... websites). Manu ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Pb building HDBC-sqlite3
Hello still, trying to use a database with ghc 6.8.1 - patience running low however :) I now have troubles installing HDBC-sqlite3 the build fails like so : $ runhaskell Setup.lhs build Preprocessing library HDBC-sqlite3-1.1.3.0... Utils.hsc:31:33: error: hdbc-sqlite3-helper.h: No such file or directory Utils.hsc: In function ‘main’: Utils.hsc:70:0: error: parse error before ‘finalizeonce’ compiling dist/build/Database/HDBC/Sqlite3/Utils_hsc_make.c failed command was: /usr/local/bin/ghc -c -package base-3.0.0.0 -package mtl-1.1.0.0 -package HDBC-1.1.3 -I. dist/build/Database/HDBC/Sqlite3/ Utils_hsc_make.c -o dist/build/Database/HDBC/Sqlite3/Utils_hsc_make.o the hdbc-sqlite3-helper.h file is nowhere to be found on my system should it be part of the package ? Thanks M ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Pb builind hdbc-sqlite3 (suite)
Hello, Still trying to build hdbc-sqlite3 it appears that the hdbc-sqlite3 package on Hackage is missing the C header file It is included with the hdbc-sqlite3 package found at http:// software.complete.org/hdbc-sqlite3/downloads however. Now I have another pb : Building HDBC-sqlite3-1.1.3.0... [3 of 7] Compiling Database.HDBC.Sqlite3.Utils ( dist/build/Database/ HDBC/Sqlite3/Utils.hs, dist/build/Database/HDBC/Sqlite3/Utils.o ) Database/HDBC/Sqlite3/Utils.hsc:74:8: parse error on input `import' manu:/Volumes/data/Downloads/HDBC/hdbc-sqlite3 manu$ line 74 is : foreign import ccall unsafe sqlite3.h sqlite3_errmsg I've checked and I have a sqlite3.h file in /usr/include what is this parse error on input `import' about ??? Thanks M___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Pb builind hdbc-sqlite3 (the end)
Hello
I should think a bit before posting to the list, sorry for the
pollution !
this error :
Database/HDBC/Sqlite3/Utils.hsc:74:8: parse error on input `import'
manu:/Volumes/data/Downloads/HDBC/hdbc-sqlite3 manu$
can be avoided by adding ForeignFunctionInterface to the extensions
in the .cabal file
I also had to add EmptyDataDecls to the extensions
and since adding PatternSignatures cause a parse error (see http://
hackage.haskell.org/trac/hackage/attachment/ticket/160/cabal-1.2.0-
extensions.patch)
I added this pragma {-# LANGUAGE PatternSignatures #-}
at the top of Statement.hsc and Connection.hs
It did build ! Victory !
M
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[Haskell-cafe] Haskell and DB : giving up
Hello I've spent a few days trying to install all the packages required to use HaskellDB with either MySQL or SQlite3 (the only 2 DB the host I was thinking about is supporting) Well, I am giving up ! I seriously regret replacing ghc-6.6 with ghc-6.8, I didn't expect that building packages would be so ... unsucessfull and time-wasting. I just thought I'd let you know what's in store for PHP-style-users- like-me who want to use a database with ghc-6.8.1 at the moment, the hurdle is high ! I hope these packages will be fixed soon (I can't figure how to fix them myself obviously). And now I'm going to stay away from my computer for a while :) cheerio M ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Haskell-Cafe Digest, Vol 51, Issue 180
I'm trying to build diverse packages from Hackage with ghc 6.8.1,
they usually fail to build because of missing language extensions.
Sometimes I am unable to determine the proper name of the extension
missing in .cabal
I tend to slap {- #OPTIONS -fglasgow-exts #-} at the top of the
troublesome file.
It works, but out of curiosity, what is the downside of such an
approach ? (bigger executables ?)
Can you list which packages failed to build out of the box?
-- Don
Well I'd say none of the packages I've tried, build out of the box,
that include :
haskelldb
haskelldb-hdbc
haskelldb-hdbc-sqlite3
HDBC
HDBC-sqlite3
Agreed some of these compile right after tweeking the build-depends:
and extensions: lines in the .cabal file
(apart from the pesky PatternSignatures which require a LANGUAGE
pragma in the source file)
haskelldb-hdbc-sqlite3 is the one that I couldn't get past...
I didn't bother with hsql-mysql-1.7 since Duncan Coutts mentioned it
required significant work (and I cannot do much)
Manu
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[Haskell-cafe] Cabal and DB packages
Hello, I'm trying to do something that should be fairly simple, installing some DB package so I can use MySQL or SQLite. However I've had troubles building HSQL, HaskellDB and Takusen before giving up (I am using ghc 6.8.1 and Cabal-1.2.2.0). -- with HSQL : Database/HSQL.hsc:66:7: Could not find module `System.Time': it is a member of package old-time-1.0.0.0, which is hidden so I added 'old-time' to the 'build-depends' line in the .cabal file but then it fails building with Building hsql-1.7... [1 of 2] Compiling Database.HSQL.Types ( Database/HSQL/Types.hs, dist/ build/Database/HSQL/Types.o ) Database/HSQL/Types.hs:134:18: Not in scope: type variable `forall' Database/HSQL/Types.hs:134:25: Not in scope: type variable `a' Database/HSQL/Types.hs:134:27: Illegal operator `.' in type `forall a . (Int - FieldDef - (FieldDef - CString - Int - IO a) - IO a)' (Use -XTypeOperators to allow operators in types) etc... At this point, it goes over my head... --- What the hell, I'll use HaskellDB and FlatDB, but then I get this message while building HaskellDB : src/Database/HaskellDB/HDBRec.hs:106:11: Illegal signature in pattern: l f a Use -XPatternSignatures to permit it when I add 'PatternSignatures' to the 'Extensions:' line in .cabal, it fails configuring with : Setup.hs: haskelldb.cabal:8: Parse of field 'extensions' failed: Jsus, nevermind, I'll try Takusen --- with Takusen : $ runhaskell Setup.hs configure Setup.hs:26:7: Could not find module `Distribution.Program': Use -v to see a list of the files searched for. I give up... Is there any simple way to do it though ? Is there any problems with Cabal that I need to work around ? Help !! Manu ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] WideFinder
Haskell is conspicuously absent from the languages used to tackle Tim Bray's Wide Finder problem (http://www.tbray.org/ongoing/When/200x/ 2007/10/30/WF-Results?updated). So far we have Ocaml, Erlang, Python, Ruby, etc... Bryan quickly wrote a program on his blog (http://www.serpentine.com/ blog/2007/09/25/what-the-heck-is-a-wide-finder-anyway/) that would place Haskell right in the second position. JoCaml is the fastest so far (http://eigenclass.org/hiki.rb?fast- widefinder)... Can Haskell do better ? Care to take a shot ? Manu ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why can't Haskell be faster?
From what I've seen of Clean it seems almost like Haskell. It even distributes a Haskell-Clean translator so the obvious question is, why is Haskell slower? It's also something I've wondered about, and I'm curious about the answer... One of the differences between Haskell and Clean is how side-effects are allowed (Uniqueness Types for Clean, and Monadic I/O for Haskell) GHC also supports a lot of extensions beyong Haskell98. Does it explain the difference in performances ? I don't know... Experts please ! Manu ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] What algorithm to use ?
Hello I am not sure it is appropriate to post to this mailing list to inquire about a peculiar algorithm, if not let me know... I was looking at one particular puzzle posted on the Facebook site, 'Wiretaps' (http://www.facebook.com/jobs_puzzles/?puzzle_id=11). Briefly, you have 26 programmers (numbers 1 to 26) which need to be assigned a job (a name to decode). Even numbered programmers spend 1.5 hours more per vowel. Odd ones spend 1 hour more per consonant. And finally, each programmer whose number share primes factors with the length of the name to decode, spend 2 hours extra per factor (For example, it takes programmer 12 -- factors of 2 and 3 -- an extra 4 hours to decode 'NORMAN') The point is to come up with the combination of (programmer, name) which minimizes the time taken overall. Now the simplest solution, conceptually, is calculating the time taken by each combination, and pick the fastest... However looking at the number of permutations (26! = 40329146112660563558400), quickly dampened my enthusiasm... There must be some algorithm (dynamic programming ?), that cuts down the number of calculations involved in order to find the right combination. But I cannot identify the proper algorithm to use... Can someone give me a tip ? Can some of the computations be parallelized ? (it's not an assignment, nor will I send anything to Facebook, I am just trying this out of curiosity) Thank you ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Suspected stupid Haskell Question
The problem there is that nub is O(n^2). Is there a place where one can look up the complexity of Standard Libraries functions ? E.D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Tiny documentation request
On Sep 11, 2007, at 9:58 PM, Miguel Mitrofanov wrote: Well, I'm not a web designer, but I did work with few of them, and it seems to me that you either create a table design in two hours or spend three days trying to create a CSS one and THEN create a table design in two hours. That's an exaggeration. It's widely accepted than tables can straightforwardly be dropped in most cases. They are intented to be used to present tabular datas, NOT for layout. (This ideas is not new, Zeldman talked about it in 2001) It does require a bit of CSS-Fu, however, as CSS support in browsers varies... But hey, you've got to occupy these HTML-CSS guys ! Emmanuel___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Tiny documentation request
On Sep 11, 2007, Simon Marlow wrote: Please, please, someone do this for me. I tried, and failed, to get the layout right for the contents list in all browsers at the same time. The semantics of CSS is beyond my comprehension. Cheers, Simon Hi Simon, On the page http://www.haskell.org/ghc/docs/latest/html/libraries/ index.html, you only need tables to display the foldable lists of modules (HTML tables were commonly used to display many things on a same line), but they can be replaced by nested lists with a bit of CSS : Check this page out : http://la.di.da.free.fr/haddock/ I can help further, if need be. Emmanuel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Tiny documentation request
Neil Mitchell wrotes : Replicating actual tables with CSS is a nightmare - you shouldn't use table's for lots of things, I agree but there are sometimes when it really is the best option. Which isn't the case here ! Nested lists would easily do the trick... Fixing up the CSS and still keeping tables is a perfectly valid option. yes it's true... E.D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Norvig's Sudoku Solver in Haskell
Daniel Fischer's modifications to my original program lead to a 400 % speed boost !!! (It now runs in 22 seconds on my machine) He avoided unecessary calls to 'length', uses Array instead of Map, refactored 'search' function (details below) I've put up his version on hpaste : http://hpaste.org/2452#a1 Manu On Aug 26, 2007, at 10:56 PM, Daniel Fischer wrote: Without much thinking I can spped it up by a factor of 4 (from 280s to 60s). The most important things are: - don't use length unless you need it instead of newV2 - case length newCell of 0 - Nothing ... and case length dPlaces of 0 - ... use case newCell of [] - Nothing [d'] - ... and case dPlaces of [] - Nothing [s'] - ... - let dPlaces = [ s' | u - lookup s units, s' - u, elem d (lookup s' newV2)] is bad let dPlaces = [s' | s' - lookup s peers, elem d (lookup s' newV2)] scans each peer only once - search is really bad, you lookup all squares several times, potentially compute all lengths multiple times... much better is search :: Grid - Maybe Grid search g = case [(l,a) | a@(_,xs) - M.assocs g, let l = length xs, l /= 1] of [] - return g ls - do let (_,(s,ds)) = minimum ls msum [assign g (s,d) = search | d - ds] (I also changed the type, and instead of foldl' you should use foldr, since some is lazy in the second argument, further, since Maybe is a MonadPlus, it's mplus and 'foldr mplus Nothing' is msum) - Maps aren't good here, too slow lookup and you know the keys, so use arrays ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Norvig's Sudoku Solver in Haskell
From: Daniel Fischer Thought it was something like that. Must check whether that beats Norvig's constraint propagation. it does ! on my machine : Jon Harrop's : 12.5 sec and Norvig's : 15 sec Manu ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Norvig's Sudoku Solver in Haskell
Hello,
After reading Peter Norvig's take on writing a Sudoku solver (http://
norvig.com/sudoku.html)
I decided that I would port his program to Haskell, without changing
the algorithm, that'll make a nice exercise I thought
and should be fairly easy... Boy, was I wrong !
Anyway, I eventually managed to tiptoe around for loops, mutable
state, etc...
However, when I run my program against the test data provided (http://
norvig.com/top95.txt),
I find it takes around 1m20 s to complete (compiled with -fvia-C and -
O2, on a MacBook Pro 2.33GHz Intel Core 2 Duo).
That's roughly 8 times longer than Norvig's Python script. That's not
what I expected !
My program is also longer than the Python version.
Being a beginner, I am convinced my implementation is super naive and
non idiomatic. A seasonned Haskeller would do much shorter and much
faster. I don't know how to improve it though !
Should I introduce more strictness ? replace lists with more
efficient data structures (ByteStrings, Arrays) ?
Here is my program, and part of the profiling (memory allocation
looks huge !)
I hope this post wasn't too long. Thanks for any advice !
Emmanuel.
{-
This is an attempt to implement in Haskell, Peter Norvig's sudoku
solver :
Solving Every Sudoku Puzzle (http://norvig.com/sudoku.html)
In Norvig's program, methods which change a grid return either a new
grid, either False (failure).
Here I use Maybe, and return Just grid or Nothing in case of failure
-}
module Main where
import Prelude hiding (lookup)
import Data.List hiding (lookup)
import qualified Data.Map as M
import Control.Monad
import Maybe
import System.IO
--
-- Types
type Digit = Char
type Square = String
type Unit = [Square]
-- We represent our grid as a Map
type Grid = M.Map Square [Digit]
--
-- Setting Up the Problem
rows = ABCDEFGHI
cols = 123456789
digits = 123456789
cross :: String - String - [String]
cross rows cols = [ r:c:[] | r - rows, c - cols ]
squares :: [Square]
squares = cross rows cols -- [A1,A2,A3,...]
unitlist :: [Unit]
unitlist = [ cross rows [c] | c - cols ] ++
[ cross [r] cols | r - rows ] ++
[ cross rs cs | rs - [ABC,DEF,GHI], cs -
[123,456,789]]
units :: M.Map Square [Unit]
units = M.fromList [ (s, [ u | u - unitlist, elem s u ]) | s -
squares ]
peers :: M.Map Square [Square]
peers = M.fromList [ (s, set [[ p | p - e, p /= s ] | e - lookup s
units ]) | s - squares ]
where set = nub . concat
--
-- Wrapper around M.lookup used in list comprehensions
lookup :: (Ord a, Show a) = a - M.Map a b - b
lookup k v = case M.lookup k v of
Just x - x
Nothing - error $ Error : key ++ show k ++ not
in map !
-- lookup k m = fromJust . M.lookup k m
--
-- Parsing a grid into a Map
parsegrid :: String - Maybe Grid
parsegrid g= do regularGrid g
foldM assign allPossibilities (zip squares g)
where allPossibilities :: Grid
allPossibilities = M.fromList [ (s,digits) | s - squares ]
regularGrid :: String - Maybe String
regularGrid g = if all (\c - (elem c 0.-123456789)) g
then (Just g)
else Nothing
--
-- Propagating Constraints
assign:: Grid - (Square, Digit) - Maybe Grid
assign g (s,d) = if (elem d digits) then do -- check that we are
assigning a digit and not a '.'
let toDump = delete d (lookup s g)
res - foldM eliminate g (zip (repeat s) toDump)
return res
else return g
eliminate :: Grid - (Square, Digit) - Maybe Grid
eliminate g (s,d) = let cell = lookup s g in
if not (elem d cell) then return g -- already
eliminated
-- else d is deleted from s' values
else do let newCell = delete d cell
newV = M.insert s newCell g --
newV2 - case length newCell of
-- contradiction :
Nothing terminates the computation
0 - Nothing
-- if there is only one
value (d2) left in square, remove it from peers
1 - do let peersOfS =
[ s' | s' - lookup s peers ]
res - foldM
eliminate newV (zip peersOfS (cycle newCell))
return res
-- else : return the new
grid
_ - return newV
-- Now check
Re: [Haskell-cafe] Norvig's Sudoku Solver in Haskell
From: Malte Milatz [EMAIL PROTECTED] Subject: Re: [Haskell-cafe] Norvig's Sudoku Solver in Haskell Your program was wrapped by your mail client, so you may want to hpaste your program for easier digestion. here it is : http://hpaste.org/2452 Your profiling output suggests that much time is consumed by the lookup function. Since you're using (fromJust . lookup) everywhere anyway, a data structure not envolving the Maybe type is probably a more succint choice. And why bother with characters and strings? no rationale except that's what the original Python script did use newV2 - case length newCell of 0 - Nothing 1 - do let peersOfS = [ s' | s' - lookup s peers ] res - foldM eliminate newV (zip peersOfS (cycle newCell)) return res _ - return newV The use of “length” here is not an actual performance problem, but unnecessary. Simply write: case newCell of [] - ... [_] - ... _ - ... The same is valid for your other use of length. Malte I see, thanks ! E.D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Building c2hs on a mac
Hello,
I'd be interested to know if anybody had managed to build c2hs on a
mac recently
because I've tried the current darcs version, c2hs-0.14.5,
c2hs-0.14.3, c2hs-0.13.6, etc...
to no avail
I get this with c2hs-0.14.5 :
./Setup.hs configure
./Setup.hs:11:57:
Couldn't match expected type
`Distribution.PackageDescription.PackageDescription'
against inferred type `LocalBuildInfo'
Probable cause: `addWrapperAndLib' is applied to too many arguments
In the `postInst' field of a record
In the first argument of `defaultMainWithHooks', namely
`defaultUserHooks {postInst = addWrapperAndLib}'
Any help appreciated, thanks
E.D
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