- Haskell-Cafe - Haskell.org

Re: [Haskell-cafe] Problems with building GCJNI 1.2
by Antony Courtney 22 Feb '05

22 Feb '05

Hi, Sorry for not jumping in on this discussion sooner. I am the author of GCJNI. GCJNI was developed back when Hugs was the dominant Haskell implementation and GreenCard was the easiest/best way to do foreign language bindings for Haskell because the FFI proposal was still in the formative stages. These days, the Haskell FFI addendum is stable and widely implemented, ghc has become much more widely available and easy to install and use, and (without wishing to sound harsh), GreenCard's FFI code generator was broken and useless the last time I tried to use it (a few years ago). I actually ported GCJNI to the Haskell FFI a few years ago, getting rid of ALL use of GreenCard. I used ghc's 'hsc2hs' tool to help with the marshalling, and made no attempt to port to hugs. I called this newer system 'hsjni'. It worked very well for my needs (using the Java2D rendering engine as the back-end for a prototype Haskell GUI system). I never released hsjni simply due to lack of time while finishing my thesis. I invested a little effort in trying to test hsjni with the latest JDK and get a release together in December, but it got snagged on a silly little bug in hsc2hs's handling of paths which have embedded spaces. A minor bug, to be sure, but since the default installation location for the JDK under Windows is under "C:\Program Files", the bug meant hsjni couldn't work out-of-the-box for the most common installation of the prerequisites. Simon Marlow has since fixed this bug in CVS head; I'm just waiting for the next release of ghc with this fix available before I try again. If you think you'd be interested in having a shot at building 'hsjni' (or you are interested in maintaining it), let me know, and I'll make the sources available for you. Caveat is that I haven't tested it since JDK 1.3, because of this hsc2hs issue. My appologies for not mentioning any of the above on the GCJNI web page. Hopefully the whole GCJNI release and web pages can be deprecated soon, with hsjni offered in its place. Kind Regards, -Antony -- Antony Courtney email: antony(a)aya.yale.edu New York, NY WWW: http://www.apocalypse.org/~antony

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[darcs #222] performance problem with massive changes in a single file
by David Roundy via RT 22 Feb '05

22 Feb '05

I'm cc'ing haskell-cafe on this darcs bug, since I imagine there might be a student (or professor) hanging around there who might be interested in the implementation of an efficient LCS algorithm in haskell. [markjugg - Sun Feb 20 09:15:57 2005]: > Typically in software, 1000's of line aren't changed at the time, which > is why this hasn't been an big issue before. Indeed. The issue here is that darcs uses the exact Hunt-Szymanski LCS algorithm when it computes the diff, while GNU diff uses an approximate --but faster--algorithm, which works "almost" as well. The approximate algorithm is reasonably well-documented, but more complex to implement than the exact one, just because it's harder to understand. This would be a reasonable project for an interested haskell CS student. The LCS is implemented in pure haskell 98, and is of signature lcs :: Ord a => [a] -> [a] -> [a] It's an interesting problem that's easily testable, and has different scaling behavior in different limits (finite alphabet, infinite alphabet, permutations of unique objects). David (ever optimistic for new contributors to darcs!) http://darcs.net

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ANN: Haskell news/community site
by John Goerzen 22 Feb '05

22 Feb '05

Hi, I'm setting up a Haskell news & community site. Check it out at: http://sequence.complete.org/ It supports aggregation of Haskell blogs and discussion from various sources (including this list). Any registered user can submit content for the front page, and all registered users can vote to approve or reject such submissions. The first thing to do is pick a real name. I hope that eventually this can be a *.haskell.org site. -- John

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Alternative lambda syntax (not entirely serious)
by Fritz Ruehr 22 Feb '05

22 Feb '05

I was introducing a fresh set of students to lambda abstraction in Haskell yesterday and had the following inspiration about a possible alternative syntax. I didn't end up showing the idea to the students -- too confusing -- but I thought I would float it here, as long as nobody takes it too seriously (this is the Cafe, after all :) ) . The idea arose from two things I'd done recently in class: introducing the underscore pattern as "an anonymous variable", and also commenting on the relationship between the final "->" in a type signature and the "=" of the corresponding function definition. So, since a lambda abstraction denotes an anonymous function, the underscore signifies anonymous things, and given that "->" of the current syntax connotes a type than a value, I thought "why not this syntax instead?": (_ x = x) -- the identity function (_ (x,y) = x) -- the fst function (_ f g x = f (g x)) -- composition In other words, at a lexical level we simply write "_" in place of "\" and "=" in place of "->". The use and placement of the "_" nicely indicates that what we are denoting is both anonymous and a function, and the use of the "=" makes it more parallel to the definition of a named function. This looks pretty nice in the right context, e.g., when talking about the kinds of code transformation one does when introducing lambda. For example: foo = map f xs where f x = blah VERSUS foo = map (_ x = blah) xs OK, so why not a serious proposal? Well first off, from a pedagogical perspective, we may not *want* to stress the similarity between the definition of a function and an expression which denotes one: this is a point of some confusion for newcomers, after all. Second, I imagine it could make parsing more difficult (although an *initial* underscore wouldn't otherwise come up in an expression context, right?). Third (and this is probably the death-knell), the use of "_" and "=" would be especially confusing in cases where an abstraction appears immediately on the RHS of a definition, or where one of the parameter patterns was itself an underscore. Or (and especially!) both; for example: const = (_ x _ = x) -- bleah! or worse yet: const x = (_ _ = x) -- yikes! Now, such definitions don't come up much in actual production code, I suppose, but they do tend to come up in classrooms, where the basic ideas are being introduced, and confusion would be especially unwelcome there. Finally, and not least, this proposal would further distance Haskell's syntax from the original lambda notation: this is not only a sad thing in general, but it would also make lambda-based T-shirt & merchandise logos even more obscure than they are now :) . -- Fritz

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Strange HTTP module behavior
by John Goerzen 22 Feb '05

22 Feb '05

Hello, I am trying to send a simple SOAP message to an Apache server. I got the HTTP library from the XML-RPC library and thought this would make an easy client. However, I'm having two problems. First, even though I am sending an accurate Content-Length header with my POST message, the server is timing out and returning a 500 Internal Server Error document. Second, after reading that error document, Network.HTTP is generating an error of its own. Here's an strace illustrating it: recvfrom(3, "ssResponse> </soapenv:Body>\n</soapenv:Envelope>", 1000, 0, NULL, N ULL) = 47 recvfrom(3, "", 1000, 0, NULL, NULL) = 0 shutdown(3, 1 /* send */) = 0 shutdown(3, 0 /* receive */) = 0 close(3) = 0 ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 fcntl(2, F_GETFL) = 0x8002 (flags O_RDWR|O_LARGEFILE|0x800 0) write(2, "\nFail: ", 7) = 7 write(2, "Network.Socket.recv: end of file (end of file)\n", 47) = 47 write(2, "\n", 1) = 1 I *think* that what's happening is that ghc threw an exception for the empty recvfrom response, then the exception handler closed the conection, and then the exception was prnited to stderr. Oh, tcpdump verified that both client and server are sending Connection: close headers. Any ideas? -- John

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Re: Strange HTTP module behavior [PATCH]
by John Goerzen 21 Feb '05

21 Feb '05

On Fri, Feb 18, 2005 at 11:36:57PM +0100, Bjorn Bringert wrote: > John Goerzen wrote: > >It turns out that Network.Socket.recv raises an EOF error when it gets > >back 0 bytes of data. HTTP is expecting it to return an empty list for > >some reason. > > > >The below patch fixed it for me. > > [...] > > Hmm, strange. Is that recv behavior a bug or a feature? I don't know, but it's explicitly there whatever it is. From ghc 6.2.2: let len' = fromIntegral len if len' == 0 then ioError (mkEOFError "Network.Socket.recv") else peekCStringLen (ptr,len') It appears this change was committed to fptools in version 1.26 of Socket.hsc on July 15, 2002. http://cvs.haskell.org/cgi-bin/cvsweb.cgi/fptools/libraries/network/Network… Which arguably is not what one would expect recv to do, and in any case is undocumented at http://www.haskell.org/ghc/docs/latest/html/libraries/network/Network.Socke… Still, 2002 was awhile back, so I'm still surprised nobody else noticed. -- John

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Re: [Haskell-cafe] Literate Haskell
by yeoh＠cs.wisc.edu 20 Feb '05

20 Feb '05

> Date: Fri, 18 Feb 2005 21:21:00 +0100 > From: Dmitri Pissarenko <mailing-lists(a)dapissarenko.com> > > Hello! > > I'm curious what experienced Haskellers think about using literate > Haskell in daily work. > > It seems to me like a good idea, since during coding it often helps to > write down one's thoughts (often, I find a solution to a complicated > problem in this way). I use LHS by default. Here's some stats on the single LHS file I've been hacking away at: Lines of comments over code: 53% Char count of comments/code: 49% This is for a 754-line file. I'm real big on notes/comments, since I have often stared in bewilderment at my own code years later wondering what the heck I was doing. The puzzlement is unusual; normally, it's a good laugh. I use TextPad, and some of the comments are sidelined Haskell snippets, like on a pasteboard. Syntax coloring is active throughout the file, except in comments enclosed by "--/", which is my little kludge on TextPad to get it to work out right. Works nicely so far.

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ANN: Cabal 0.5 (GHC 6.4 release candidate)
by Isaac Jones 20 Feb '05

20 Feb '05

This is a release-candidate for 0.6, which will be in GHC 6.4. http://www.haskell.org/cabal/download.html The Haskell Cabal The Common Architecture for Building Applications and Libraries. http://www.haskell.org/cabal IMPORTANT INFORMATION: See both the README file and the changelog for important interface changes. DOWNLOAD: The Haskell Cabal has reached pre-release stage. The community should use this release to evaluate the interfaces and explore the concepts of these tools. Download the Cabal here (source and debian versions available): http://www.haskell.org/cabal/download.html BUGS: Please report bugs and wish-list items to libraries(a)haskell.org and Isaac Jones: ijones(a)syntaxpolice.org. ABOUT: The Haskell Cabal is meant to be a part of a larger infrastructure for distributing, organizing, and cataloging Haskell Libraries and Tools. It is an effort to provide a framework for developers to more effectively contribute their software to the Haskell community. Specifically, the Cabal describes what a Haskell package is, how these packages interact with the language, and what Haskell implementations must to do to support packages. The Cabal also specifies some infrastructure (code) that makes it easy for tool authors to build and distribute conforming packages. The Cabal is only one contribution to the larger goal. In particular, the Cabal says nothing about more global issues such as how authors decide where in the module name space their library should live; how users can find a package they want; how orphan packages find new owners; and so on. NOTES: You cannot currently execute the setup scripts with "./Setup.lhs" since Cabal Hugs support isn't ready-for-prime-time. You can compile it with ghc thusly: "ghc -package Cabal Setup.lhs -o setup" and then use the "setup" executable after that. This release is meant to provide the community with concrete information about how the interfaces are shaping up. This release does NOT fix the interfaces, we can't promise not to break anything that relies on these interfaces. We hope that Haskell authors will try to package their software using these tools, and let us know where they fall short. MORE INFORMATION: Please see the web site for the source code, interfaces, and especially the proposal, which will serve as documentation for this release: http://www.haskell.org/cabal/

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Problems with building GCJNI 1.2
by Dmitri Pissarenko 19 Feb '05

19 Feb '05

Hello! I am trying to build GCJNI 1.2 under Windows (cygwin) with GHC 6.2.1 and Green Card 3.01. I am getting following error messages when entering "make". <error-messages> $ make make -C src make[1]: Entering directory `/cygdrive/c/dapWork/temp/downloads/gcjni/gcjni- 1.2/ src' gcc -MM -I/cygdrive/c/Programme/Java/jdk1.5.0/include -I./win32 > .c_dependences jniInit.c util.c || (rm -f .c_dependences ; exit 1) m4 JNI.m4 > JNI.hs m4 GCJNI.m4 > GCJNI.gc /cygdrive/c/Programme/GreenCard/lib/greencard-3.01/greencard-bin --target ghc - i /cygdrive/c/Programme/GreenCard/lib/greencard-3.01/imports -- libdir=/cygdrive/c/ Programme/GreenCard/lib/greencard-3.01/ GCJNI.gc Warning: unable to find StdDIS along the import path: /cygdrive/c/Programme/Gree nCard/lib/greencard-3.01/, /cygdrive/c/Programme/GreenCard/lib/greencard- 3.01/im ports, user error ("GCJNI.gc", proc. spec "gcJniJObjectToString", line 139: marshall: Don't know how to marshall (declare { jniObjRef_t * } oref in (J Object (foreign oref {jniFreeObjRef}))) "GCJNI.gc", proc. spec "jniGetJVMState", line 156: Don't know how to unmarshall ((JVM (addr vmp)),(JEnv (addr envp))) "GCJNI.gc", proc. spec "jniGetEnv", line 160: Don't know how to unmarshall (JEnv (addr envp)) "GCJNI.gc", proc. spec "jniFreeVM", line 167: marshall: Don't know how to marshall (JVM (addr vm)) "GCJNI.gc", proc. spec "jniAddClassPath", line 181: marshall: Don't know how to marshall (string s) "GCJNI.gc", proc. spec "jniAddJVMOpt", line 188: marshall: Don't know how to marshall (string s) "GCJNI.gc", proc. spec "jniFindClass", line 192: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "jniIsInstanceOf", line 200: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniExceptionOccurred", line 206: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "jniExceptionDescribe", line 211: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "jniExceptionClear", line 215: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniDeleteLocalRef", line 224: marshall: Don't know how to marshall (declare { jniObjRef_t * } oref in (J Object (foreign oref {jniFreeObjRef}))) "GCJNI.gc", proc. spec "jniNewLocalRef", line 230: marshall: Don't know how to marshall (declare { jniObjRef_t * } lsrc in (J Object (foreign lsrc {jniFreeObjRef}))) "GCJNI.gc", proc. spec "jniNewGlobalRef", line 239: marshall: Don't know how to marshall (declare { jniObjRef_t * } loref in ( JObject (foreign loref {jniFreeObjRef}))) "GCJNI.gc", proc. spec "jniGetStaticMethodID", line 248: marshall: Don't know how to marshall (declare { jniObjRef_t * } cls in (JO bject (foreign cls {jniFreeObjRef}))) "GCJNI.gc", proc. spec "jniGetMethodID", line 255: marshall: Don't know how to marshall (declare { jniObjRef_t * } cls in (JO bject (foreign cls {jniFreeObjRef}))) "GCJNI.gc", proc. spec "jniGetStaticFieldID", line 263: marshall: Don't know how to marshall (declare { jniObjRef_t * } cls in (JO bject (foreign cls {jniFreeObjRef}))) "GCJNI.gc", proc. spec "jniGetFieldID", line 270: marshall: Don't know how to marshall (declare { jniObjRef_t * } cls in (JO bject (foreign cls {jniFreeObjRef}))) "GCJNI.gc", proc. spec "jniNewStringUTF", line 277: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "jniNewObjectArray", line 285: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniObjToJValue", line 295: marshall: Don't know how to marshall (declare { jniObjRef_t * } oref in (J Object (foreign oref {jniFreeObjRef}))) "GCJNI.gc", proc. spec "gcJniObjFromJValue", line 304: marshall: Don't know how to marshall (addr jvalp) "GCJNI.gc", proc. spec "jniPushLocalFrame", line 311: marshall: Don't know how to marshall (int count) "GCJNI.gc", proc. spec "gcJniIntToJValue", line 325: marshall: Don't know how to marshall (int val) "GCJNI.gc", proc. spec "gcJniIntFromJValue", line 330: marshall: Don't know how to marshall (addr jvalp) "GCJNI.gc", proc. spec "gcJniFloatToJValue", line 335: marshall: Don't know how to marshall (float val) "GCJNI.gc", proc. spec "gcJniFloatFromJValue", line 340: marshall: Don't know how to marshall (addr jvalp) "GCJNI.gc", proc. spec "gcJniDoubleToJValue", line 345: marshall: Don't know how to marshall (double val) "GCJNI.gc", proc. spec "gcJniDoubleFromJValue", line 350: marshall: Don't know how to marshall (addr jvalp) "GCJNI.gc", proc. spec "gcJniBoolToJValue", line 355: marshall: Don't know how to marshall (bool val) "GCJNI.gc", proc. spec "gcJniBoolFromJValue", line 360: marshall: Don't know how to marshall (addr jvalp) "GCJNI.gc", proc. spec "gcJniCharToJValue", line 365: marshall: Don't know how to marshall (char val) "GCJNI.gc", proc. spec "gcJniCharFromJValue", line 370: marshall: Don't know how to marshall (addr jvalp) "GCJNI.gc", proc. spec "gcJniAllocJValue", line 377: marshall: Don't know how to marshall (int nv) "GCJNI.gc", proc. spec "gcJniFree", line 386: marshall: Don't know how to marshall (addr a) "GCJNI.gc", proc. spec "gcJniCallStaticVoidMethod", line 391: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallVoidMethod", line 396: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallNonvirtualVoidMethod", line 401: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetStaticObjectField", line 406: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetObjectField", line 414: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallStaticObjectMethod", line 422: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallObjectMethod", line 430: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallNonvirtualObjectMethod", line 439: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetStaticIntField", line 451: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetIntField", line 457: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallStaticIntMethod", line 463: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallIntMethod", line 469: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallNonvirtualIntMethod", line 474: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetStaticCharField", line 481: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetCharField", line 487: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallStaticCharMethod", line 493: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallCharMethod", line 499: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallNonvirtualCharMethod", line 504: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetStaticByteField", line 511: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetByteField", line 517: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallStaticByteMethod", line 523: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallByteMethod", line 529: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallNonvirtualByteMethod", line 534: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetStaticFloatField", line 541: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetFloatField", line 547: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallStaticFloatMethod", line 553: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallFloatMethod", line 559: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallNonvirtualFloatMethod", line 564: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetStaticDoubleField", line 571: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetDoubleField", line 577: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallStaticDoubleMethod", line 583: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallDoubleMethod", line 589: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallNonvirtualDoubleMethod", line 594: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetStaticBooleanField", line 601: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetBooleanField", line 607: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallStaticBooleanMethod", line 613: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallBooleanMethod", line 619: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniCallNonvirtualBooleanMethod", line 624: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniNewObject", line 635: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniIsSameObject", line 649: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniGetObjectClass", line 658: marshall: Don't know how to marshall (JEnv (addr env)) "GCJNI.gc", proc. spec "gcJniAllocArgLocals", line 677: marshall: Don't know how to marshall (int capacity) "GCJNI.gc", proc. spec "gcJniFreeArgLocals", line 682: marshall: Don't know how to marshall (addr als) ) make[1]: *** [GCJNI.hs] Error 1 make[1]: Leaving directory `/cygdrive/c/dapWork/temp/downloads/gcjni/gcjni- 1.2/s rc' make: *** [src] Error 2 </error-messages> I think that the error is caused by missing StdDIS file in the GreenCard directory. The files in this directory are (ls -lAR): <filelist> .: total 0 drwxr-xr-x+ 2 eleonora Kein 0 Feb 15 21:55 bin drwxr-xr-x+ 3 eleonora Kein 0 Feb 15 21:47 lib ./bin: total 1 -rwxr-xr-x 1 eleonora Kein 164 Feb 15 21:55 greencard ./lib: total 0 drwxr-xr-x+ 4 eleonora Kein 0 Feb 15 21:55 greencard-3.01 ./lib/greencard-3.01: total 1867 drwxr-xr-x+ 2 eleonora Kein 0 Feb 15 21:55 Foreign -rwxr-xr-x 1 eleonora Kein 1895082 Feb 15 21:55 greencard-bin.exe drwxr-xr-x+ 3 eleonora Kein 0 Feb 15 21:55 imports -rwxr-xr-x 1 eleonora Kein 6612 Feb 15 21:55 libHSgreencard.a -rwxr-xr-x 1 eleonora Kein 8670 Feb 15 21:55 libHSgreencard.p_a ./lib/greencard-3.01/Foreign: total 4 -rwxr-xr-x 1 eleonora Kein 3309 Feb 15 21:55 GreenCard.gc ./lib/greencard-3.01/imports: total 0 drwxr-xr-x+ 2 eleonora Kein 0 Feb 15 21:55 Foreign ./lib/greencard-3.01/imports/Foreign: total 16 -rwxr-xr-x 1 eleonora Kein 7392 Feb 15 21:55 GreenCard.hi -rwxr-xr-x 1 eleonora Kein 7397 Feb 15 21:55 GreenCard.p_hi </filelist> As you see, there is no StdDIS file among them. AFAIK, the installation of GreenCard 3.01 was successful. I would like to receive a hint about how this problem can be solved. TIA Dmitri Pissarenko -- Dmitri Pissarenko Software Engineer http://dapissarenko.com

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new Haskell hacker seeking peer review
by Sean Perry 18 Feb '05

18 Feb '05

I am learning Haskell, so I decided to implement everyone's favorite, overused Unix command -- cat. Below is my simple implementation, comments about style, implementation, etc. are welcomed. In particular, is my untilEOF idiomatically ok? Is there a better way to accomplish this? Also, while talking about untilEOF, it is slightly annoying that hIsEOF returns IO Bool and that functions like 'not' only want Bool. Sure makes the logic tests feel like more work than they should be. cat.hs: module Main where import IO import System(getArgs) untilEOF :: Handle -> (Handle -> IO ()) -> IO () untilEOF hdl f = do eof <- hIsEOF hdl if eof then return () else do f hdl untilEOF hdl f cat :: Handle -> IO () cat hdl = do line <- hGetLine hdl putStrLn line catFile :: FilePath -> IO () catFile path = do hdl <- openFile path ReadMode untilEOF hdl cat main :: IO () main = do args <- getArgs if (length args) > 0 then mapM_ catFile args else untilEOF stdin cat

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