Re: [Haskell-cafe] ping haskell.org timeout
Jason Dagit dag...@gmail.com writes: Lots of servers turn off ICMP packet responses these days Because users don't really need error messages, that's privileged information for system administrators. Besides, if someone is trying to debug http protocol issues using ICMP, they're taking an awfully indirect route. Yes, first thing would be to check the log files. Oh, wait, users don't have read permissions for those... I think the reason it gets disabled is typically well intentioned. And we all know where that road leads - to frustration and low quality services, that's where. Sorry for my grumpiness - this is a constant struggle for me. :-) It takes a while to complete with no visual feedback. Perhaps the network is just slow? Or perhaps the web pages are cached somewhere along the way? All of those are plausible [..] Perhaps 'cabal update' should provide some visual feedback by default? There's -v, but there's still a noticable pause (15 seconds on a fairly beefy computer and a good connection) between Downloaded to [..] and Reading available packages The index is 3MB, it's probably not big enough that a smarter protocol (rsync/rdiff?) would improve things? Except perhaps checking that it has been updated since the last update - that'd probably save a ton of bandwidth if/when people do automatic updates. -k -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: shelltestrunner 1.1
On Thu, Aug 25, 2011 at 20:56, Simon Michael si...@joyful.com wrote: I'm pleased to announce shelltestrunner 1.1. shelltestrunner tests command-line programs or arbitrary shell commands. It reads simple declarative tests specifying a command, some input, and the expected output, error output and exit status. Tests can be run selectively, in parallel, with a timeout, in color, and/or with differences highlighted. Projects using it include hledger, yesod, and berp. shelltestrunner is free software released under GPLv3+. New in 1.1: * bump process dependency to allow building with GHC 7.2.1 * new `-a/--all` flag shows all failure output without truncating Home page: http://joyful.com/shelltestrunner Install: $ cabal install shelltestrunner Excellent, my strategy worked. I've been expecting this email. ;) /M -- Magnus Therning OpenPGP: 0xAB4DFBA4 email: mag...@therning.org jabber: mag...@therning.org twitter: magthe http://therning.org/magnus ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] hoogle data no connection to host http://code.galois.com/darcs/haskell-platform ...
Hi, i installed Hoogle succesfullly with cabal install hoogle then i try to run hoogle data but the connection to http://code.galois.com/darcs/haskell-platform/haskell-platform.cabal times out. How can i download the data needed for the hoogle command line tool? Greetings Chris ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] hoogle data no connection to host http://code.galois.com/darcs/haskell-platform ...
The Galois link works fine for me now - it also worked for me earlier today when I ran hoogle data for my own system. I suggest you try again, possibly with a better internet connection? Cheers, Thomas On Fri, Aug 26, 2011 at 12:39 AM, informationen informatio...@gmx.de wrote: Hi, i installed Hoogle succesfullly with cabal install hoogle then i try to run hoogle data but the connection to http://code.galois.com/darcs/haskell-platform/haskell-platform.cabal times out. How can i download the data needed for the hoogle command line tool? Greetings Chris ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] a minor bug (memory leak) in ListLike package
On Wed, Aug 24, 2011 at 3:47 PM, Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com wrote:
I was just trying to remember some of the tricks Daniel Peebles (aka
{co}pumpkin) used to do in #haskell with Data.List.genericLength.
I've never really used ListLike, but was just trying to guess why the
default implementation was as it is.
Maybe he used lazy implementations of Num and Ord in combination with
a definition like
length [] = 0
length (_:xs) = 1 + length xs
But as John observed, the accumulating version of length does not
provide such laziness and the accumulator might as well be made
strict.
Sebastian
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[Haskell-cafe] Dynamic loading of module
Hello, I stumbled upon this blog post describing a method from dynamically loading modules using GHC api. While trying to test the given method, I got the following error which obviously tells me my packages are not correctly installed but I have no idea how to fix this. D:\projets\ghc -package ghc main.hs --make command line: cannot satisfy -package ghc: ghc-7.0.3-fc75cf67c86ba2c0d64b07024a18d3b4 is unusable due to missing or recursive dependencies: template-haskell-2.5.0.0-7d9b1443ac5ab69e5ed705a487990deb (use -v for more information) When I run ghc-pkg check, I got which obviously is bad. There are problems in package test-framework-0.3.3: dependency regex-posix-0.94.4-7963833a181f95ba404a78e3e76d835a doesn't exist There are problems in package QuickCheck-2.4.0.1: dependency template-haskell-2.5.0.0-e5fd973432385747440288b48f6a6a5a doesn't exist There are problems in package snap-0.5.1: dependency attoparsec-0.8.6.1-3d4c24cfa94f97cbeb7d6cf43ef70284 doesn't exist dependency blaze-builder-0.3.0.1-157e8a92bc5ef27895f938613ecfdcb1 doesn't exist dependency cereal-0.3.3.0-81dac2655ecff64c5fc69671490df093 doesn't exist dependency enumerator-0.4.10-d65a90206db2a5203c1c906e6f58a6c9 doesn't exist There are problems in package snap-server-0.5.1: dependency attoparsec-0.8.6.1-3d4c24cfa94f97cbeb7d6cf43ef70284 doesn't exist dependency attoparsec-enumerator-0.2.0.3-d5a7e5b640b4b27be4c6d0c9a314dd0a doesn't exist dependency binary-0.5.0.2-72c84eaab351d41e936261d8d5d416f5 doesn't exist dependency blaze-builder-0.3.0.1-157e8a92bc5ef27895f938613ecfdcb1 doesn't exist dependency case-insensitive-0.2.0.1-6cb260512f91ae60284372c0208aa00e doesn't exist dependency enumerator-0.4.10-d65a90206db2a5203c1c906e6f58a6c9 doesn't exist There are problems in package snap-core-0.5.1: dependency attoparsec-0.8.6.1-3d4c24cfa94f97cbeb7d6cf43ef70284 doesn't exist dependency attoparsec-enumerator-0.2.0.3-d5a7e5b640b4b27be4c6d0c9a314dd0a doesn't exist dependency blaze-builder-0.3.0.1-157e8a92bc5ef27895f938613ecfdcb1 doesn't exist dependency case-insensitive-0.2.0.1-6cb260512f91ae60284372c0208aa00e doesn't exist dependency enumerator-0.4.10-d65a90206db2a5203c1c906e6f58a6c9 doesn't exist There are problems in package heist-0.5.2: dependency attoparsec-0.8.6.1-3d4c24cfa94f97cbeb7d6cf43ef70284 doesn't exist dependency blaze-builder-0.3.0.1-157e8a92bc5ef27895f938613ecfdcb1 doesn't exist There are problems in package xmlhtml-0.1.5: dependency blaze-builder-0.3.0.1-157e8a92bc5ef27895f938613ecfdcb1 doesn't exist There are problems in package authenticate-0.9.0.1: dependency attoparsec-0.8.6.1-3d4c24cfa94f97cbeb7d6cf43ef70284 doesn't exist dependency blaze-builder-0.3.0.1-157e8a92bc5ef27895f938613ecfdcb1 doesn't exist dependency case-insensitive-0.2.0.1-6cb260512f91ae60284372c0208aa00e doesn't exist dependency enumerator-0.4.10-d65a90206db2a5203c1c906e6f58a6c9 doesn't exist There are problems in package http-enumerator-0.6.5.1: dependency attoparsec-0.8.6.1-3d4c24cfa94f97cbeb7d6cf43ef70284 doesn't exist dependency attoparsec-enumerator-0.2.0.3-d5a7e5b640b4b27be4c6d0c9a314dd0a doesn't exist dependency blaze-builder-0.3.0.1-157e8a92bc5ef27895f938613ecfdcb1 doesn't exist dependency case-insensitive-0.2.0.1-6cb260512f91ae60284372c0208aa00e doesn't exist dependency enumerator-0.4.10-d65a90206db2a5203c1c906e6f58a6c9 doesn't exist There are problems in package zlib-enum-0.2.1: dependency enumerator-0.4.10-d65a90206db2a5203c1c906e6f58a6c9 doesn't exist There are problems in package yesod-static-0.1.0: dependency cereal-0.3.3.0-81dac2655ecff64c5fc69671490df093 doesn't exist dependency pureMD5-2.1.0.3-cb7a7a936930b56c62f9207838b99efb doesn't exist There are problems in package yesod-form-0.1.0.1: dependency blaze-builder-0.3.0.1-157e8a92bc5ef27895f938613ecfdcb1 doesn't exist dependency data-default-0.2.0.1-14197e607852c0357951d749c098bd34 doesn't exist There are problems in package yesod-core-0.8.2: dependency blaze-builder-0.3.0.1-157e8a92bc5ef27895f938613ecfdcb1 doesn't exist dependency case-insensitive-0.2.0.1-6cb260512f91ae60284372c0208aa00e doesn't exist dependency cereal-0.3.3.0-81dac2655ecff64c5fc69671490df093 doesn't exist dependency enumerator-0.4.10-d65a90206db2a5203c1c906e6f58a6c9 doesn't exist There are problems in package warp-0.4.0.1: dependency blaze-builder-0.3.0.1-157e8a92bc5ef27895f938613ecfdcb1 doesn't exist dependency case-insensitive-0.2.0.1-6cb260512f91ae60284372c0208aa00e doesn't exist dependency enumerator-0.4.10-d65a90206db2a5203c1c906e6f58a6c9 doesn't exist There are problems in package wai-extra-0.4.0.1: dependency blaze-builder-0.3.0.1-157e8a92bc5ef27895f938613ecfdcb1 doesn't exist dependency case-insensitive-0.2.0.1-6cb260512f91ae60284372c0208aa00e doesn't exist dependency enumerator-0.4.10-d65a90206db2a5203c1c906e6f58a6c9 doesn't exist There are problems in package wai-app-static-0.1.0: dependency
[Haskell-cafe] Make shared library - questions
Hi ! I'm trying to compile shared library. This library will use as part of plugin for some program. If I compile library with option -dynamic my library has links for HS libraries like libHSbase-4.2.0.2-ghc6.12.3.so and so on. But program has crashed constantly. Is it possible to make shared library without -dynamic flag? I want to try to make library without dependencies. According to http://www.well-typed.com/blog/30 theoretically I can do this but I found this impossible - http://hackage.haskell.org/trac/ghc/ticket/3704 My options to compile: ghc -O2 --make -no-hs-main -dynamic -shared -fPIC -optl '-shared' -optc '-DMODULE=MyLib' -o MyLib.so MyLib.hs module_init.c -optl-Wl -lHSrts-ghc6.12.3 If I try compile without -dynamic I get error: /usr/bin/ld: /usr/local/lib/ghc-6.12.3/base-4.2.0.2/libHSbase-4.2.0.2.a(Conc__270.o): relocation R_X86_64_32 against `base_GHCziConc_ensureIOManagerIsRunning1_closure' can not be used when making a shared object; recompile with -fPIC /usr/local/lib/ghc-6.12.3/base-4.2.0.2/libHSbase-4.2.0.2.a: could not read symbols: Bad value collect2: ld returned 1 exit status My system is: Cenos 5.6 ghc6.12.3 gcc-4.2.1 Cheers, Sergiy ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Make shared library - questions
On 26 August 2011 13:52, Sergiy Nazarenko nazarenko.ser...@gmail.com wrote: /usr/local/lib/ghc-6.12.3/base-4.2.0.2/libHSbase-4.2.0.2.a(Conc__270.o): relocation R_X86_64_32 against `base_GHCziConc_ensureIOManagerIsRunning1_closure' can not be used when making a shared object; recompile with -fPIC So it looks like you will have to recompile the base libraries with -fPIC (or try this on Windows, where PIC is unnecessary). The way I would do this personally is to recompile all of GHC, and in mk/build.mk set the GhcLibHcOpts to -fPIC. There may be a way to just recompile the base library (and dependents) using Cabal, but I'm less sure about that path. Note that using -fPIC will probably impose a performance penalty on the library code. Max ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Ambiguous module name `System.Directory'
Hi, i am using ghc version 7.0.3 and a pretty recent version of the haskell-platform. Whenever i use the System.Directory module, i run into this conflict: Ambiguous module name `System.Directory': it was found in multiple packages: system-fileio-0.2.1 directory-1.1.0.0 How can i resolve this conflict permamently (i know about :set -hide-package ... )? And shouldn't there be a rule in the haskell platform which forbids modules of the same name? Greetings Chris ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Ambiguous module name `System.Directory'
On 26 August 2011 18:00, informationen informatio...@gmx.de wrote: Hi, i am using ghc version 7.0.3 and a pretty recent version of the haskell-platform. Whenever i use the System.Directory module, i run into this conflict: Ambiguous module name `System.Directory': it was found in multiple packages: system-fileio-0.2.1 directory-1.1.0.0 How can i resolve this conflict permamently (i know about :set -hide-package ... )? And shouldn't there be a rule in the haskell platform which forbids modules of the same name? 1) Use PackageImports: http://www.haskell.org/ghc/docs/7.0.3/html/users_guide/syntax-extns.html#package-imports import network Network.Socket 2) Use cabal-dev ghci which will only have packages available that you specify in your .cabal file. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] hledger subcommand detection, RFC
Thanks Conrad! Those are some great links. I wrapped up some manpage generation code in a package called ui-command, which is kind of orthogonal to cmdargs (ui-command just deals with subcommands). Example commands are often useful, so I added Interesting. Have you tried using both ui-command and cmdargs together ? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] bitSize
On 26/08/2011 02:40 AM, Daniel Peebles wrote: And as Daniel mentioned earlier, it's not at all obvious what we mean by bits used when it comes to negative numbers. I guess part of the problem is that the documentation asserts that bitSize will never depend on its argument. (So would will write things like bitSize undefined :: ThreadID or similar.) I can think of several possible results one might want from a bit size query: 1. The number of bits of precision which will be kept for values of this type. (For Word16, this is 16. For Integer, this is [almost] infinity.) 2. The amount of RAM that this value is using up. (But that would surely be measured in bytes, not bits. And processor registors make the picture more complicated.) 3. The bit count to the most significant bit, ignoring sign. 4. The bit count to the sign bit. Currently, bitSize implements #1. I'm not especially interested in #2. I would usually want #3 or #4. Consider the case of 123 (decimal). The 2s complement representation of +123 is ...000011 The 2s complement representation of -123 is ...111101 For query #3, I would expect both +123 and -123 to yield 7. For query #4, I would expect both to yield 8. (Since if you truncate both of those strings to 8 bits, then the positive value starts with 0, and the negative one start with 1.) Then of course, there's the difference between count of the bits and bit index, which one might expect to be zero-based. (So that the Nth bit represents 2^N.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] bitSize
On Friday 26 August 2011, 19:24:37, Andrew Coppin wrote: On 26/08/2011 02:40 AM, Daniel Peebles wrote: And as Daniel mentioned earlier, it's not at all obvious what we mean by bits used when it comes to negative numbers. I guess part of the problem is that the documentation asserts that bitSize will never depend on its argument. (So would will write things like bitSize undefined :: ThreadID or similar.) I don't think that's a problem, it's natural for what bitSize does. And it would be bad if bitSize did something different for Integer than for Int, Word, ... I can think of several possible results one might want from a bit size query: Yup, though for some there are better names than bitSize would be. 1. The number of bits of precision which will be kept for values of this type. (For Word16, this is 16. For Integer, this is [almost] infinity.) Not almost infinity, what your RAM or Int allow, whichever cops out first, or enough, unless you [try to] do really extreme stuff. 2. The amount of RAM that this value is using up. (But that would surely be measured in bytes, not bits. And processor registors make the picture more complicated.) 3. The bit count to the most significant bit, ignoring sign. 4. The bit count to the sign bit. Currently, bitSize implements #1. I'm not especially interested in #2. I would usually want #3 or #4. I'd usually be more interested in #2 than in #4. Consider the case of 123 (decimal). The 2s complement representation of +123 is ...000011 The 2s complement representation of -123 is ...111101 For query #3, I would expect both +123 and -123 to yield 7. One could make a case for the answer 3 for -123, I wouldn't know what to expect without it being stated in the docs. For query #4, I would expect both to yield 8. (Since if you truncate both of those strings to 8 bits, then the positive value starts with 0, and the negative one start with 1.) #4 would then generally be #3 + 1 for signed types, I think, so not very interesting, but for unsigned types? Then of course, there's the difference between count of the bits and bit index, which one might expect to be zero-based. (So that the Nth bit represents 2^N.) Yes, but that shouldn't be a problem with good names. So, which of them are useful and important enough to propose for inclusion? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] bitSize
On Fri, 26 Aug 2011 18:24:37 +0100, you wrote: I would usually want #3 or #4. Out of curiosity, what for? While I do occasionally need to get a logarithmic size estimate of a number (which is basically what #3 and #4 are), the specific requirements in each case tend to vary, enough so that it's unlikely that a single function (other than simply taking the logarithm) can handle the majority of applications. -Steve Schafer ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] bitSize
On 26/08/2011 07:36 PM, Steve Schafer wrote: On Fri, 26 Aug 2011 18:24:37 +0100, you wrote: I would usually want #3 or #4. Out of curiosity, what for? While I do occasionally need to get a logarithmic size estimate of a number (which is basically what #3 and #4 are), the specific requirements in each case tend to vary, enough so that it's unlikely that a single function (other than simply taking the logarithm) can handle the majority of applications. You wouldn't want to know how many bits you need to store on disk to reliably recreate the value? Or how many bits of randomness you need to compute a value less than or equal to this one? I suppose I could use a binary logarithm. I'm just concerned that it would be rather slow. After all, I'm not interested in the exact logarithm (which is fractional), just the number of bits (which is a small integer)... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] RFC: decodeFloat
Occasionally, the behaviour of decodeFloat and its consequences causes concern and/or bug reports (e.g. http://hackage.haskell.org/trac/ghc/ticket/3898). The main problem is the treatment of NaNs and infinities (that it doesn't distinguish between 0.0 and -0.0 is a minor thing), which are converted as if they were ordinary finite values. Thus, for example, decodeFloat (1/0 :: Double) = (2^52,972) and consequently floor (1/0 :: Double) = 2^1024 (corresponding for round, truncate, ceiling, properFraction), significand (1/0 :: Double) = 0.5, Prelude uncurry encodeFloat (decodeFloat (1/0 :: Float)) :: Double 3.402823669209385e38 and similar meaningless/nonsensical results for NaNs. At its type, decodeFloat :: RealFloat a = a - (Integer, Int), I see only two reasonable options, 1. leave the behaviour as it is, just warn about the exceptional cases in the documentation, 2. let decodeFloat raise an error when its argument is a NaN or infinite. Both options have disadvantages, 1. makes it easy to get meaningless results when there's a non-finite value around, 2. incurs a nontrivial performance penalty. Paying that performance penalty when dealing only with known-to-be-good values is undesirable, but so are meaningless results. A third option would be providing both behaviours by adding a function. That could take several forms, a) leave decodeFloat as is and add safeDecodeFloat outside the RealFloat class, that would check the value first and then either raise an error on NaN/Infinity or return a Maybe (Integer, Int), b) add a function to the RealFloat class, either leave decodeFloat as is and add safeDecodeFloat with the behaviour as in a) or change decodeFloat according to 2. and add unsafeDecodeFloat with the current behaviour. The drawback of a) is that safeDecodeFloat would have to perform two checks, while with IEEE Doubles/Floats, the result could be determined by one check (which would also be simpler than each of isNaN and isInfinite). Also, which module should export it? The drawback of b) is adding a function to RealFloat, as if that wasn't big enough already. Since both behaviours allow a default definition in terms of the other, only code that by chance uses the new name would break. What would be the community's preferred way to handle this issue? Cheers, Daniel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] bitSize
On Friday 26 August 2011, 21:30:02, Andrew Coppin wrote: You wouldn't want to know how many bits you need to store on disk to reliably recreate the value? Or how many bits of randomness you need to compute a value less than or equal to this one? I suppose I could use a binary logarithm. I'm just concerned that it would be rather slow. After all, I'm not interested in the exact logarithm (which is fractional), just the number of bits (which is a small integer)... As of GHC-7.2, there's GHC.Integer.Logarithms in both, integer-gmp and integer-simple, providing integerLog2# :: Integer - Int# (integer-* lives before base, so there's no Int yet) which exploits the representation of Integers and should be fast enough [at least for integer-gmp, where it's bounded time for normally represented values, the representation of Integers in integer-simple forces it to be O(log n)]. Caution: integerLog2# expects its argument to be positive, havoc might ensue if it isn't. GHC.Float exports integerLogBase :: Integer - Integer - Int also before 7.2, now it calls the above if the base is 2, so should have decent performance. (It requires that the base is 1 and the second argument positive, of course.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Dynamic loading of module
On 11-08-26 04:51 AM, Arnaud Bailly wrote: D:\projets\ghc -package ghc main.hs --make command line: cannot satisfy -package ghc: ghc-7.0.3-fc75cf67c86ba2c0d64b07024a18d3b4 is unusable due to missing or recursive dependencies: template-haskell-2.5.0.0-7d9b1443ac5ab69e5ed705a487990deb (use -v for more information) When I run ghc-pkg check, I got which obviously is bad. [...] There are problems in package QuickCheck-2.4.0.1: dependency template-haskell-2.5.0.0-e5fd973432385747440288b48f6a6a5a doesn't exist For a 100%-accurate answer, one would need the full history of what you did to your computer, which no one knows. For a 99%-accurate answer, the outputs of ghc -v and ghc-pkg list -v are very good post-mortem information. A 90%-accurate answer: Given the incomplete information (that's right, ghc-pkg check is incomplete), there is 90% probability that you lost template-haskell, and you must reinstall haskell platform. (No, building a new instance of template-haskell is not enough. Generally, replacing or overriding libs that come with GHC does not work. See my http://www.vex.net/~trebla/haskell/sicp.xhtml ) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Ambiguous module name `System.Directory'
On 11-08-26 12:00 PM, informationen wrote: How can i resolve this conflict permamently (i know about :set -hide-package ... )? And shouldn't there be a rule in the haskell platform which forbids modules of the same name? Two permanent resolutions, choose one: ghc-pkg hide system-fileio ghc-pkg unregister system-fileio Haskell platform has never included system-fileio, so it contains no ambiguous module name. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] bitSize
On Fri, 26 Aug 2011 20:30:02 +0100, you wrote: You wouldn't want to know how many bits you need to store on disk to reliably recreate the value? I can't say that I have cared about that sort of thing in a very long time. Bits are rather cheap these days. I store data on disk, and the space it occupies is whatever it is; I don't worry about it. Or how many bits of randomness you need to compute a value less than or equal to this one? I'm not sure I understand this one. I generally don't need _any_ randomness to compute a value. On the other hand, if the desire is to take an integer n and generate a set of pseudorandom numbers ranging from 0 to n-1, that's easily done using the standard random number methods. -Steve Schafer ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Project Euler: request for comments
Hi, I order to improve my Haskell skills I started (again) to solve the project euler problems with this language. I am now at problem 11 and would really appreciate any comment about my code in order to make it more elegant or efficient. My solutions can be found here: http://fp.opicasso.com/tag/projecteuler Oscar Picasso ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Project Euler: request for comments
Is Problem 11 the 4 consecutive #'s problem? If so what must be true for 4 #'s to have a large product? Hint: x * y * z * 2 is that going to be larger? -- -- Regards, KC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to make callCC more dynamic
Thank you, there is also a nice link here :-)
http://stackoverflow.com/questions/7178919/how-to-make-callcc-more-dynamic
and for this type,
ContT {runContT :: forall r1 . (forall r2 . a- m r2) - m r1}
callCC can be defined, however, you can not run it, and reset couldn't
type check
于 11-8-25 上午1:53, o...@okmij.org 写道:
bob zhang wrote:
I thought the right type for ContT should be
newtype ContT m a = ContT {runContT :: forall r. (a- m r) - m r}
and
other control operators
shift :: Monad m = (forall r . (a- ContT m r) - ContT m r) - ContT m a
reset :: Monad m = ContT m a - ContT m a
callCC :: ((a- (forall r . ContT m r)) - ContT m a) - ContT m a
unfortunately, I can not make callCC type check, and don't know how to
do it.
Precisely that problem was discussed in
http://okmij.org/ftp/continuations/undelimited.html#proper-contM
Your ContT is CPS1 in the above article. The article shows why you
cannot write callCC with the above type of ContT. The article talks
about other types. BTW, if you faithfully defined the monad for
undelimited control than shift/reset cannot be expressed. Undelimited
continuations are strictly less expressible than delimited ones. The
above page gives the pointers to the papers with the proof.
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