- Haskell-Cafe - Haskell.org

Same compiled program behaving differently when called from ghci and shell
by Bruno Damour 21 Nov '10

21 Nov '10

Hello, I have a very strange (for me) problem that I manage to reduce to this : I have a small program that reads a file with 1 only character (è = e8) The program is ftest2.hs : import IO import Data.Maybe tfind s = lookup (head s) $ zip ['\xe8', '\xde'] "12" main = do h<- readFile "g:\\CODE\\rlib\\test.txt" putStrLn h print $ tfind h I compile it from command line : ghc --make ftest2.hs Now the weird results : 1/ cmd line: ftest2.exe è Just '2' 2/ ghci Prelude> :!ftest2.exe è Just '2' 3/WinGHci Prelude> :! ftest2.exe è Just '1' I tested different variants, there is always a difference. Any idea to help me trace this behaviour ?

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OT: Mailing list for testing email
by Alexander Solla 21 Nov '10

21 Nov '10

Hi everybody This is kind of off topic, but mailing list related. I've been messing around with my email server, to help fix some issues with the new version of Postfix (with regards to my old configuration). I seem to be receiving email intermittently. Does anybody know of a mailing list for email testing? I mean, I would like to be able to "spam" the mailing list with test messages and receive other people's test messages, until I'm sure my configuration is working right, without bothering the Cafe (or any other topic specific list). I know there used to be usenet groups for this purpose, but that's usenet, not email. I guess it would be nice if somebody sent me a quick pong in response to my ping, but I don't want to make too much noise here. Thanks

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Catching up on Time and Directory
by Jon Fairbairn 21 Nov '10

21 Nov '10

I'm probably terribly out of date with this, so I wonder if anyone can save me the bother of working out what the /preferred/ libraries are for (a) determining the last-modified-time of a file or directory and (b) manipulating the resulting time datum. I can find System.Directory.getModificationTime and Data.Time.formatTime, but using them together seems unduly awkward. -- Jón Fairbairn Jon.Fairbairn(a)cl.cam.ac.uk http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2010-09-14)

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Codec.Crypto.RSA question
by Charles-Pierre Astolfi 21 Nov '10

21 Nov '10

Hi -cafe, I have a question about Codec.Crypto.RSA: how to enforce that (informally) decrypt . encrypt = id Consider this code: encrypt2 :: String -> ByteString encrypt2 = fst . encrypt (mkStdGen n) pubKey encode decrypt2 :: ByteString -> String decrypt2 = toString . decrypt privKey Since decrypt2 takes a bytestring which size is a multiple of the modulus, I've guessed that the encrypted bytestring is padded with '\NUL' characters. But then some strange stuff shows up: decrypt2 $ encrypt2 "haskell" returns "\NUL\NUL\NUL\NUL\EOThaskell" decrypt2 $ encrypt2 "foobar" returns "\NUL\NUL\NUL\NUL\65533foobar" I may use dropWhile to get rid of the NUL-padding, but can I assume that I'll always get a random character between my string and the padding? I tried to pad myself with NUL characters but I got almost the same results (the "random char" went to the head of the string) -- Cp

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Making HList's field access operators (#) and (.!.) left-associative?
by Josh Triplett 21 Nov '10

21 Nov '10

Hello, In experimenting with HList's very impressive extensible records, I discovered that the field access operators (#) and (.!.) have right associativity; this means I can't write (r # f1 # f2) to access field f2 of the record stored in field f1 of r. If (#) and (.!) had left-associativity instead, then I could write such nested record operations. As far as I can tell, the right-associative binding would only make sense if attempting to store field labels inside a record, which seems much more unlikely. I wrote to the author of HList about this issue, and he agreed that this sounded reasonable, but he wanted me to confirm via haskell-cafe that nobody had code which relied on the existing behavior. Comments? Objections? Thanks, Josh Triplett

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Tooltips on tree view rows
by José Romildo Malaquias 21 Nov '10

21 Nov '10

Hello. I need the gtk_tree_view_set_tooltip_column from Gtk+, but it seems tht it has not been ported to gtk2hs. Is it the case? How can I easily add tooltips to rows in a TreeView? Regards, Romildo

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trouble with HDBC-mysql on Mac OS X
by Mark Lentczner 21 Nov '10

21 Nov '10

I'm having trouble with HDBC-mysql on Mac OS X (10.6, Snow Leopard). It compiles and builds fine, but when loaded (into ghci), the dynamic loader complains about not being able to find libmygcc.dylib. The issue is, MySQL's libmygcc is a static lib, not a dynamic one, so of course it won't find it. I've checked the build sequence that HDBC-mysql uses, and it calls upon mysql_config to generate the lib options. I've checked those and they are correct, expressly listing libmygcc statically (!). I've tried building against both the 64bit and 32bit versions of MySQL libs. (Suspect that only the 32bit should work.) Anyone have HDBC-mysql running on 10.6? Any ideas for me to try would be appreciated. - Mark Mark Lentczner http://www.ozonehouse.com/mark/ IRC: mtnviewmark

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ghc panic when compiling blaze-builder
by José Romildo Malaquias 21 Nov '10

21 Nov '10

When compiling blaze-builder-0.2.0.1 with ghc-7.0.1 on my ~amd64 gentoo system, I am getting the shown below. Any clues? Romildo [...] Building blaze-builder-0.2.0.1... [1 of 8] Compiling Blaze.ByteString.Builder.Internal ( Blaze/ByteString/Builder/Internal.hs, dist/build/Blaze/ByteString/Builder/Internal.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.0.1 for x86_64-unknown-linux): dsLet: unlifted AbsBinds [b{tv aUH} [sk]] [] [pe{v axd} [lid] <= [b{tv aUH} [sk]] pe{v aUG} [lid]] pe{v axd} [lid] :: forall b{tv aUH} [sk]. base:GHC.Ptr.Ptr{tc 33A} b{tv aUH} [sk] [LclId] { {273:19-54} {273:19-54} !((pe{v aUG} [lid] :: base:GHC.Ptr.Ptr{tc 33A} b{tv aUH} [sk])) = {273:30-54} {273:33-41} (base:GHC.Ptr.plusPtr{v r4X} [gid]) @ base:GHC.Word.Word8{tc 32U} @ b{tv aUH} [sk] pf{v axc} [lid] firstBufSize{v arR} [lid] } EvBinds{{}} base:GHC.Base.>>={v 01P} [gid[ClassOp]] @ <nt>ghc-prim:GHC.Types.IO{tc 32I} $dMonad{v aUI} [lid] @ blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BuildSignal{tc rre} @ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5} (step0{v arY} [lid] pf{v axc} [lid] (pe{v axd} [lid] @ base:GHC.Word.Word8{tc 32U})) (\ (next{v axT} [lid] :: blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BuildSignal{tc rre}) -> let { ds_d15b{v} [lid] :: blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BuildSignal{tc rre} [LclId] ds_d15b{v} [lid] = next{v axT} [lid] } in case ds_d15b{v} [lid] {ghc-prim:GHC.Types.IO{tc 32I} bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}} of (wild_B1{v} [lid] :: blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BuildSignal{tc rre}) { blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.Done{d rrk} (rb_d15l{v} [lid] :: ghc-prim:GHC.Prim.Addr#{(w) tc 33}) -> let { pf'{v axU} [lid] :: base:GHC.Ptr.Ptr{tc 33A} base:GHC.Word.Word8{tc 32U} [LclId] pf'{v axU} [lid] = base:GHC.Ptr.Ptr{v rcP} [gid[DataCon]] @ base:GHC.Word.Word8{tc 32U} rb_d15l{v} [lid] } in let { fail_d15c{v} [lid] :: ghc-prim:GHC.Prim.State#{(w) tc 32q} ghc-prim:GHC.Prim.RealWorld{(w) tc 31E} -> ghc-prim:GHC.Types.IO{tc 32I} bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5} [LclId] fail_d15c{v} [lid] = \ (ds_d15d{v} [lid] :: ghc-prim:GHC.Prim.State#{(w) tc 32q} ghc-prim:GHC.Prim.RealWorld{(w) tc 31E}) -> base:GHC.Base.${v 019} [gid] @ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5} @ (ghc-prim:GHC.Types.IO{tc 32I} bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}) (base:GHC.Base.return{v 01T} [gid[ClassOp]] @ <nt>ghc-prim:GHC.Types.IO{tc 32I} $dMonad{v aUN} [lid] @ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}) (bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.$WChunk{v reF} [gid[DataConWrapper]] (mkbs{v axe} [lid] @ base:GHC.Word.Word8{tc 32U} pf'{v axU} [lid]) k{v arT} [lid]) } in case base:GHC.Classes.=={v 01L} [gid[ClassOp]] @ (base:GHC.Ptr.Ptr{tc 33A} base:GHC.Word.Word8{tc 32U}) $dEq{v aUK} [lid] pf'{v axU} [lid] pf{v axc} [lid] {ghc-prim:GHC.Types.IO{tc 32I} bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}} of (wild_B1{v} [lid] :: ghc-prim:GHC.Bool.Bool{(w) tc 3c}) { ghc-prim:GHC.Bool.False{(w) d 68} -> fail_d15c{v} [lid] ghc-prim:GHC.Prim.realWorld#{(w) v 0o} [gid]; ghc-prim:GHC.Bool.True{(w) d 6u} -> base:GHC.Base.return{v 01T} [gid[ClassOp]] @ <nt>ghc-prim:GHC.Types.IO{tc 32I} $dMonad{v aUL} [lid] @ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5} k{v arT} [lid] }; blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BufferFull{d rri} (rb_d15n{v} [lid] :: ghc-prim:GHC.Prim.Int#{(w) tc 3G}) (rb_d15o{v} [lid] :: ghc-prim:GHC.Prim.Addr#{(w) tc 33}) (nextStep{v axX} [lid] :: blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BuildStep{tc rrc}) -> let { newSize{v axV} [lid] :: ghc-prim:GHC.Types.Int{(w) tc 3J} [LclId] newSize{v axV} [lid] = ghc-prim:GHC.Types.I#{(w) v 6d} [gid[DataCon]] rb_d15n{v} [lid] } in let { pf'{v axW} [lid] :: base:GHC.Ptr.Ptr{tc 33A} base:GHC.Word.Word8{tc 32U} [LclId] pf'{v axW} [lid] = base:GHC.Ptr.Ptr{v rcP} [gid[DataCon]] @ base:GHC.Word.Word8{tc 32U} rb_d15o{v} [lid] } in let { l{v aUP} [lid] :: ghc-prim:GHC.Types.Int{(w) tc 3J} [LclId] l{v aUP} [lid] = base:GHC.Ptr.minusPtr{v r4U} [gid] @ base:GHC.Word.Word8{tc 32U} @ base:GHC.Word.Word8{tc 32U} pf'{v axW} [lid] pf{v axc} [lid] } in case l{v aUP} [lid] {ghc-prim:GHC.Types.IO{tc 32I} bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}} of (l{v aUP} [lid] :: ghc-prim:GHC.Types.Int{(w) tc 3J}) { __DEFAULT -> let { l{v axY} [lid] :: ghc-prim:GHC.Types.Int{(w) tc 3J} [LclId] l{v axY} [lid] = l{v aUP} [lid] } in base:GHC.Base.${v 019} [gid] @ blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BuildStep{tc rrc} @ (ghc-prim:GHC.Types.IO{tc 32I} bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}) (fillNewBuffer{v arW} [lid] (base:GHC.Classes.max{v rG} [gid[ClassOp]] @ ghc-prim:GHC.Types.Int{(w) tc 3J} $dOrd{v aUQ} [lid] (base:GHC.Num.+{v r24} [gid[ClassOp]] @ ghc-prim:GHC.Types.Int{(w) tc 3J} $dNum{v aY6} [lid] l{v axY} [lid] newSize{v axV} [lid]) minBufSize{v arQ} [lid])) (\ (pfNew{v axZ} [lid] :: base:GHC.Ptr.Ptr{tc 33A} base:GHC.Word.Word8{tc 32U}) (peNew{v ay0} [lid] :: base:GHC.Ptr.Ptr{tc 33A} base:GHC.Word.Word8{tc 32U}) -> base:GHC.Base.>>{v 01Q} [gid[ClassOp]] @ <nt>ghc-prim:GHC.Types.IO{tc 32I} $dMonad{v aY7} [lid] @ ghc-prim:GHC.Unit.(){(w) tc 40} @ blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BuildSignal{tc rre} (base:Foreign.Marshal.Utils.copyBytes{v r4c} [gid] @ base:GHC.Word.Word8{tc 32U} pfNew{v axZ} [lid] pf{v axc} [lid] l{v axY} [lid]) (nextStep{v axX} [lid] (base:GHC.Ptr.plusPtr{v r4X} [gid] @ base:GHC.Word.Word8{tc 32U} @ base:GHC.Word.Word8{tc 32U} pfNew{v axZ} [lid] l{v axY} [lid]) peNew{v ay0} [lid])) }; blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.ModifyChunks{d rrg} (rb_d15q{v} [lid] :: ghc-prim:GHC.Prim.Addr#{(w) tc 33}) (bsk{v ay2} [lid] :: bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5} -> bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}) (nextStep{v ay3} [lid] :: blaze-builder-0.2.0.1:Blaze.ByteString.Builder.Internal.BuildStep{tc rrc}) -> let { pf'{v ay1} [lid] :: base:GHC.Ptr.Ptr{tc 33A} base:GHC.Word.Word8{tc 32U} [LclId] pf'{v ay1} [lid] = base:GHC.Ptr.Ptr{v rcP} [gid[DataCon]] @ base:GHC.Word.Word8{tc 32U} rb_d15q{v} [lid] } in let { fail_d15g{v} [lid] :: ghc-prim:GHC.Prim.State#{(w) tc 32q} ghc-prim:GHC.Prim.RealWorld{(w) tc 31E} -> ghc-prim:GHC.Types.IO{tc 32I} bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5} [LclId] fail_d15g{v} [lid] = \ (ds_d15h{v} [lid] :: ghc-prim:GHC.Prim.State#{(w) tc 32q} ghc-prim:GHC.Prim.RealWorld{(w) tc 31E}) -> base:GHC.Base.${v 019} [gid] @ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5} @ (ghc-prim:GHC.Types.IO{tc 32I} bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}) (base:GHC.Base.return{v 01T} [gid[ClassOp]] @ <nt>ghc-prim:GHC.Types.IO{tc 32I} $dMonad{v aYc} [lid] @ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}) (bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.$WChunk{v reF} [gid[DataConWrapper]] (mkbs{v axe} [lid] @ base:GHC.Word.Word8{tc 32U} pf'{v ay1} [lid]) (bsk{v ay2} [lid] (base:GHC.Base.${v 019} [gid] @ (ghc-prim:GHC.Types.IO{tc 32I} bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}) @ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5} (bytestring-0.9.1.8:Data.ByteString.Internal.inlinePerformIO{v riV} [gid] @ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}) (fillNewBuffer{v arW} [lid] bufSize{v arP} [lid] nextStep{v ay3} [lid])))) } in case base:GHC.Classes.=={v 01L} [gid[ClassOp]] @ (base:GHC.Ptr.Ptr{tc 33A} base:GHC.Word.Word8{tc 32U}) $dEq{v aY9} [lid] pf'{v ay1} [lid] pf{v axc} [lid] {ghc-prim:GHC.Types.IO{tc 32I} bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}} of (wild_B1{v} [lid] :: ghc-prim:GHC.Bool.Bool{(w) tc 3c}) { ghc-prim:GHC.Bool.False{(w) d 68} -> fail_d15g{v} [lid] ghc-prim:GHC.Prim.realWorld#{(w) v 0o} [gid]; ghc-prim:GHC.Bool.True{(w) d 6u} -> base:GHC.Base.${v 019} [gid] @ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5} @ (ghc-prim:GHC.Types.IO{tc 32I} bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}) (base:GHC.Base.return{v 01T} [gid[ClassOp]] @ <nt>ghc-prim:GHC.Types.IO{tc 32I} $dMonad{v aYa} [lid] @ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}) (bsk{v ay2} [lid] (base:GHC.Base.${v 019} [gid] @ (ghc-prim:GHC.Types.IO{tc 32I} bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}) @ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5} (bytestring-0.9.1.8:Data.ByteString.Internal.inlinePerformIO{v riV} [gid] @ bytestring-0.9.1.8:Data.ByteString.Lazy.Internal.ByteString{tc rg5}) (fillNewBuffer{v arW} [lid] bufSize{v arP} [lid] nextStep{v ay3} [lid]))) } })

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Interactive OpenGL-based graphics and ghci?
by Conal Elliott 21 Nov '10

21 Nov '10

I'm trying to find some way to do interactive, OpenGL-based graphics in Haskell on Mac OS X. Does anyone here use GLUT or SDL on Mac OS X with ghci, or maybe an alternative library? Using ghci is very important to me, as my programs are pretty high-level and are often half-liners. I'm using gtk2hs for now, but I want something that works more natively, i.e., without the awkwardness of going through the X server. Thanks, - Conal

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Downloading web page in Haskell
by José Romildo Malaquias 21 Nov '10

21 Nov '10

In order to download a given web page, I wrote the attached program. The problem is that the page is not being full downloaded. It is being somehow intettupted. Any clues on how to solve this problem? Romildo

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