Re: [Haskell-cafe] Bug in writeArray?
2009/9/23 Bulat Ziganshin bulat.zigans...@gmail.com: Hello Grzegorz, Wednesday, September 23, 2009, 7:19:59 PM, you wrote: This seems like a bug in the implementation of writeArray: when passed let (l,u) = ((0,10),(20,20)) writeArray computes raw index (from 0 to total number of array elements) and check that this index is correct. with multi-dimensional arrays this approach may lead to wrong results, as you mentioned. it's known problem that isn't fixed for a long time probably due to efficiency cautions. Hmm, I understand that efficiency is an issue, but in that case shouldn't unsafe writing be provided by and unsafeWriteArray function, while writeArray does proper range checking? Or at least this problem with writeArray should be clearly indicated in the documentation. I for one spent several hours debugging before finding out about this lack of proper range checks so it's not an imaginary problem. -- Grzegorz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Bug in writeArray?
Hi all, This seems like a bug in the implementation of writeArray: when passed an out-of-range index it silently writes to an incorrect index in the array. -- import Data.Array.IO import Data.Array.Unboxed main = do let (l,u) = ((0,10),(20,20)) marr - newArray (l,u) 0 :: IO (IOUArray (Int,Int) Int) let badi = (10,9) print (inRange (l,u) badi) writeArray marr badi 1 arr - freeze marr :: IO (UArray (Int,Int) Int) print . filter ((/=0) . snd) . assocs $ arr -- Grzegorz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Data.Binary.encode slower than show
Hi all, I have a piece of code where I'm serializing a datastructure with the following type [(Int, (Map DType (IntMap Int)))], using Binary.encode The thing is it is very slow: actually quite a bit slower than just using show. This seems rather suspicious. Any idea what could be going on? import qualified Data.Map as Map import qualified Data.IntMap as IntMap import Data.IntMap ((!)) import Vector import Atom import Control.Monad.State import Indexing (indexBy) import Data.List (foldl') import System import System.IO import Debug.Trace import qualified Data.Binary as Binary import qualified Data.ByteString.Lazy as BS data DType = Fol | For | Sol | Sor deriving (Eq,Enum,Ord,Show,Read) instance Binary.Binary DType where get = do x - Binary.get return (toEnum x) put x = Binary.put (fromEnum x) type Word = Int type Count = Int type WordMap = IntMap.IntMap find = IntMap.findWithDefault IntMap.empty distReps :: Map.Map (Word,Word) Count - [(Int, (Map.Map DType (WordMap Count)))] distReps bidict = let bigrams = Map.toList bidict for = indexBy id bigrams fol = indexBy swap bigrams ws = map (fst . fst) bigrams r = flip map ws $ \w - (w,Map.fromList [ (Fol , find w fol) , (For , find w for) , (Sol , sox for fol w ) , (Sor , sox fol for w ) ]) in trace (show $ r == r) r sox :: WordMap (WordMap Count) - WordMap (WordMap Count) - Word - WordMap Count sox fox foy w = let xs = IntMap.keys (find w fox) f !z x = let xv = find x foy in xv == xv `seq` z `plus` xv in foldl' f IntMap.empty xs swap (!a,!b) = (b,a) readBigrams = fmap (map (\ [w,w',c] - ((w,w'),read c)) . map words . lines ) getContents main = do [f] - getArgs bigrams - readBigrams let (bigrams',as) = flip runState empty (atomize bigrams) dr = distReps (Map.fromList bigrams') write f dr hPutStrLn stderr Done this write (f++.atom) as --write f d = writeFile f (show d) write f d = BS.writeFile f (Binary.encode d) atomize xs = mapM f xs where f ((w,w'),!i) = do !i_w - toAtom w' !i_w' - toAtom w let r = ((i_w,i_w'),i) r == r `seq` return r -- Grzegorz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Implicit params and typeclasses
Hi all,
When I try to compile the following in GHC (v 6.6) (with
-fno-monomorphism-restriction -fimplicit-params)
class Configuration a where
thestring:: a - String
foo c = let { ?c = c } in bar
bar = thestring ?c
I get:
Ambiguous type variable `a' in the constraint:
`Configuration a'
arising from use of `thestring' at /home/grzegorz/Foo.hs:9:6-17
Possible cause: the monomorphism restriction applied to the following:
bar :: (?c::a) = String (bound at /home/grzegorz/Foo.hs:9:0)
foo :: a - String (bound at /home/grzegorz/Foo.hs:8:0)
Probable fix: give these definition(s) an explicit type signature
or use -fno-monomorphism-restriction
Adding the type signature bar :: (Configuration a,?c :: a) = String
the compiler says:
Ambiguous constraint `Configuration a'
At least one of the forall'd type variables mentioned by the constraint
must be reachable from the type after the '='
In the type signature for `bar':
bar :: (Configuration a, ?c :: a) = String
Similar code without use of implicit params compiles fine:
class Configuration a where
thestring:: a - String
foo c = thestring c
Why do implicit params cause this error and is there a way to make it work?
Thanks,
--
Grzegorz
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Re: [Haskell-cafe] Haskell as embedded DSL
Perhaps Functional Morphology http://www.cs.chalmers.se/~markus/FM/, a toolkit for morphology development would be of interest. -- Grzegorz On 7/5/06, Joel Reymont [EMAIL PROTECTED] wrote: Folks, Do you have examples of using Haskell as a DSL in an environment NOT targeted at people who know it already? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
