Re: [Haskell-cafe] GHCi fails to load C++ object files (missing symbol)
On 8 Mar 2012, at 13:21, Mark Wright wrote: It might work without -fpic on x86 (32 bit): http://www.mail-archive.com/gentoo-dev@gentoo.org/msg01420.html On OS X, it is always on; I tried the example on 10.7, Xcode 4.3. I had to add ln -s /Applications/Xcode.app/Contents/Developer /Developer as ghc 7.0.4 looks for /Developer/usr/bin/gcc. For some funny reason ghc is at /usr/bin/ghc; since it is not a system distribution, it should be at /usr/local/bin/, which is also in the system path. On x86-64, there special relative addressing support, so there is no reason having it turned off, but some other good reasons for having on, like the security reason mentioned here: http://stackoverflow.com/questions/7078253/pic-on-osxs-gcc Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] C++ Parser?
On 24 Jan 2012, at 11:06, Christopher Brown wrote: I have stumbled across language-c on hackage and I was wondering if anyone is aware if there exists a full C++ parser written in Haskell? There is a yaccable grammar http://www.parashift.com/c++-faq-lite/compiler-dependencies.html#faq-38.11 You might run it through a parser generator that outputs Haskell code. http://www.haskell.org/haskellwiki/Applications_and_libraries/Compiler_tools Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] black Wikipedia (Was: PhD program at Portland State accepting applications)
On 18 Jan 2012, at 18:49, Andrew Butterfield wrote: Just add ?banner=none to the url if you really have to read the page Or stop the loading before the banner comes up. Hans On 18 Jan 2012, at 17:37, Henning Thielemann wrote: On Wed, 18 Jan 2012, Nathan Collins wrote: - Portland is a very popular US city, known for beer, bikes, music, and street food: http://en.wikipedia.org/wiki/Portland_Oregon (wikipedia is blacked out today) Maybe it is only a JavaScript trick. In Firefox (with JavaScript) I see the complete a page before it is overwritten by the protest page. In Konqueror of KDE 3 (with and without JavaScript) I can read the Wiki pages without problems. Edit however is really disabled. Sometimes I am glad to have the old technology available. :-) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] black Wikipedia
On 18 Jan 2012, at 19:32, John Meacham wrote: Not to mention ebay, craigslist, etc.. http://www.techdirt.com/articles/20111005/10082416208/monster-cable-claims-ebay-craigslist-costco-sears-are-rogue-sites.shtml when there is no burden of proof for someone to take down a site then things get very complicated. for instance this package could be enough to get all of hackage taken down since astrolabe decided they own timezone data[1]. http://hackage.haskell.org/package/timezone-olson-0.1.2 There is the Beastie Boys case, where the judge decided copyright protects what is creatively unique. Hans in fact, SOPA and PIPA would make hackage pretty impossible to legally host. Unless the hackage maintainers want to do exhaustive patent and copyright searches on all uploaded code before they allow it to be posted. [1] http://www.techdirt.com/articles/20111006/11532316235/astrolabe-claims-it-holds-copyright-timezone-data-sues-maintainers-public-timezone-database.shtml John On Wed, Jan 18, 2012 at 10:17 AM, Brandon Allbery allber...@gmail.com wrote: On Wed, Jan 18, 2012 at 13:11, Henning Thielemann lemm...@henning-thielemann.de wrote: On Wed, 18 Jan 2012, Andrew Butterfield wrote: Just add ?banner=none to the url if you really have to read the page Maybe the intention was to demonstrate that censorship (in this case self-censorship) is mostly a problem for average users but not for advanced users. There isn't going to be a disable-javascript or ?banner hack when anyone anywhere can force a website to be redirected to some DOJ page without providing any proof. (Yes, really.) -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ 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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] black Wikipedia
On 18 Jan 2012, at 23:11, Brandon Allbery wrote: There is the Beastie Boys case, where the judge decided copyright protects what is creatively unique. But such judgments are rare, sadly. And for every Beastie Boys case there's at least one The Verve case. I did not know that. But it was a UK case, wasn't it? - UK copyright laws are a lot more tight. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] black Wikipedia
Actually, it is a battle between the Hollywood and Silicon Valley industries. Hans On 19 Jan 2012, at 00:11, John Meacham wrote: And such a thing can take months or years for the courts to figure out, and unless your free site has a lawyer to fight for your side, under SOPA/PIPA you can be down the entire time with little recourse. For anyone hosting content lke hackage, github, etc. when you have thousands of packages, someone somewhere is going to be upset by something and will be able to take the site down. _regardless of the merit of their case_ the site will go down as they figure it out. Not only that, they would be able to take the site down if it contains a link to an objectionable site. for instance, if one of the homepage fields in some cabal file somewhere pointed to a site that someone took offense too on it. we would not only be obligated to patrol the code uploaded, but the targets of any urls within said code/description... and retroactively remove stuff if said links change to contain objectional material. (for a very vauge definition of objectionable). it is a really messed up law. John On Wed, Jan 18, 2012 at 2:46 PM, Hans Aberg haber...@telia.com wrote: On 18 Jan 2012, at 23:11, Brandon Allbery wrote: There is the Beastie Boys case, where the judge decided copyright protects what is creatively unique. But such judgments are rare, sadly. And for every Beastie Boys case there's at least one The Verve case. I did not know that. But it was a UK case, wasn't it? - UK copyright laws are a lot more tight. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHC exceeding command line length limit with split-objs - and a possible fix
On 11 Jan 2012, at 13:38, John Lato wrote: I used https://github.com/kennethreitz/osx-gcc-installer/downloads to get a real gcc on Lion. Biggish download, but it worked. I've also seen reports of success by self-compiling gcc, or by installing XCode 4 on top of an existing XCode 3 installation. GCC 4.6.2 builds on OS X 10.7 with Xcode 4.2. Build GMP 5.0.2 with clang, and then GCC with /usr/bin/gcc - llvm-gcc-4.2. I think I saw someone guild GCC 4.7, but this is highest stable. Hans From: Eugene Kirpichov ekirpic...@gmail.com Oh well... looks like building ghc won't be easy, as it doesn't build with llvm-gcc and it's not easy to get a real gcc on Lion. But I don't stop trying :) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] If you'd design a Haskell-like language, what would you do different?
On 26 Dec 2011, at 16:11, AUGER Cédric wrote: There is http://www.stixfonts.org/ For typesetting with Xe[La]TeX or Lua[La]TeX, use XITS (in the TeXLive package). (And then we'll have to deal with folks trying to use the letter, because everyone knows the Roman alphabet is the only one that matters and of *course* Greek letters are symbol characters Pfeh.) This is the big problem right now: how to enter these symbols efficiently. Under Xorg, XCompose might be your friend! I have a whole bunch of them for Coq programing. Having something like: -8- # ~/.XCompose contents: # the Compose file of the xorg distribution to have a lot # of useful symbols such as ☭ ^^ include /usr/local/lib/X11/locale/en_US.UTF-8/Compose # the Compose file that could be included in Haskell distributions include /usr/local/share/haskell/Compose # other personnal notations ---8--- # /usr/local/share/haskell/Compose contents: # maybe to be downloaded via a Hackage cabal package? # of course Multi_key H should be replaced by a # user specified combo Multi_key H colon colon : ∷ Multi_key H greater greater greater : ⋙ Multi_key H less less less : ⋘ Multi_key H less minus less : ↢ U2919 Multi_key H greater minus greater : ↣ U291A Multi_key H minus less less : U291B Multi_key H greater greater minus : U291C Multi_key H a l l : ∀ Multi_key H e x : ∃ Multi_key H a n d : ∧ Multi_key H o r : ∨ Multi_key H a b s t : λ Multi_key H c o m p : ∘ Multi_key H minus greater : → 8-- But if you are under Windows, or Mac OS, I cannot tell (as well as I cannot tell if you are under a POSIX system not running xorg, such as the tty1..ttyn consoles) On OS X one can make ones owns key maps, like with the program on the link below, but it is very time consuming. Hans http://scripts.sil.org/cms/scripts/page.php?site_id=nrsiid=ukelele ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] If you'd design a Haskell-like language, what would you do different?
On 26 Dec 2011, at 19:29, AUGER Cédric wrote: Le Mon, 26 Dec 2011 18:20:55 +0100, Hans Aberg haber...@telia.com a écrit : On 26 Dec 2011, at 16:11, AUGER Cédric wrote: Under Xorg, XCompose might be your friend! I have a whole bunch of them for Coq programing. Having something like: -8- # ~/.XCompose contents: # the Compose file of the xorg distribution to have a lot # of useful symbols such as ☭ ^^ include /usr/local/lib/X11/locale/en_US.UTF-8/Compose # the Compose file that could be included in Haskell distributions include /usr/local/share/haskell/Compose # other personnal notations ---8--- # /usr/local/share/haskell/Compose contents: # maybe to be downloaded via a Hackage cabal package? # of course Multi_key H should be replaced by a # user specified combo Multi_key H colon colon : ∷ Multi_key H greater greater greater : ⋙ Multi_key H less less less : ⋘ Multi_key H less minus less : ↢ U2919 Multi_key H greater minus greater : ↣ U291A Multi_key H minus less less : U291B Multi_key H greater greater minus : U291C Multi_key H a l l : ∀ Multi_key H e x : ∃ Multi_key H a n d : ∧ Multi_key H o r : ∨ Multi_key H a b s t : λ Multi_key H c o m p : ∘ Multi_key H minus greater : → 8-- But if you are under Windows, or Mac OS, I cannot tell (as well as I cannot tell if you are under a POSIX system not running xorg, such as the tty1..ttyn consoles) On OS X one can make ones owns key maps, like with the program on the link below, but it is very time consuming. http://scripts.sil.org/cms/scripts/page.php?site_id=nrsiid=ukelele I have heard of ukelele (but I didn't remembered the name as I am not a Mac OS user); I have heard it was a rather dirty solution, but that should work. I think so, too. I guess that having a Haskell (or any script language by the way) patching the xml file (and able to unpatch if we want to uninstall) and make possible to get that patch via Hackage could be a solution (it would be time consuming for the patch writer, but then any Mac OS user would benefit it). Of course it would only work for the basic Haskell notations, for custom ones, I guess it would be interesting to have a program which reads a XCompose like file (which is quite easy to edit) and generate the xml file for ukelele. Note that the rest of the Haskell cafe mailing list won't be able to read my response since it seems that I cannot post on the list (I subscribed 2 years ago and never posted; waiting to learn and Haskell and then read the mailing list, but I learnt Haskell only about one month ago). If one had a way to replace ASCII multicharacter symbols, that might be easier. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] If you'd design a Haskell-like language, what would you do different?
On 26 Dec 2011, at 23:03, Brandon Allbery wrote: But if you are under Windows, or Mac OS, I cannot tell (as well as I cannot tell if you are under a POSIX system not running xorg, such as the tty1..ttyn consoles) On OS X one can make ones owns key maps, like with the program on the link below, but it is very time consuming. System Preferences Personal Language Text Text Use symbol and text substitution Cool. I have a vague memory of seeing it, but not paying much attention to it. One can turn it on in Xcode 4.2 by Edit - Format - Substitutions - Show Substitutions and click Text Replacement or selecting it directly in the Substitutions menu. This popup windows allows one to apply it a text selection. (And similar in other programs, like Mail.) For example, I set one entry so that typing x |- a becomes x ↦ a, the TeX \mapsto, in Unicode ↦ RIGHTWARDS ARROW FROM BAR U+21A6. It might be tedious to make a lot of entries, though, but something to start with. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] If you'd design a Haskell-like language, what would you do different?
On 27 Dec 2011, at 01:02, Donn Cave wrote: Quoth Hans Aberg, ... For example, I set one entry so that typing x |- a becomes x ↦ a, the TeX \mapsto, in Unicode ↦ RIGHTWARDS ARROW FROM BAR U+21A6. It might be tedious to make a lot of entries, though, but something to start with. Something to finish me with, too. I wouldn't be able to do much in a programming world that used glyphs like that. The symbol I chose is the one normally used in math. You can see it here: https://en.wikipedia.org/wiki/Function_(mathematics) My vision isn't perfect, but I think it's within a fairly normal range, and it isn't good enough to decode a lot of hieroglyphics at normal font size at reading speed. Higher resolution displays might help, but larger ones are expected to come the next year. The ASCII limit of 100 or so normal characters may be a barrier to expression, but it's a boost to comprehension. Common combinations tend to evolve in symbols. The ASCII combinations are just makeshift. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] If you'd design a Haskell-like language, what would you do different?
On 21 Dec 2011, at 04:15, Brandon Allbery wrote: On Tue, Dec 20, 2011 at 21:05, Andrew Cowie and...@operationaldynamics.com wrote: Now we just need λ to replace \, → to replace -, and ≠ to replace /= (which still looks like division assignment no matter how hard I squint my eyes. 25 years of C and C derived languages is hard to forget). Some of it is already supported. http://www.haskell.org/ghc/docs/latest/html/users_guide/syntax-extns.html#unicode-syntax (≠ isn't in that list, but it doesn't need to be; just stick it in the Prelude if it's not there already, since it's not special syntax, it's just another operator. The * *is* a special case, I suspect, though: I bet it's only supported in kinds, not as the multiplication operator.) The one on the list is not a mathematical symbol. It should be ⋆ STAR OPERATOR U+22C6 or ∗ ASTERISK OPERATOR U+2217. The problem with λ is that it's a perfectly valid Unicode lowercase letter. There is 훌 MATHEMATICAL BOLD SMALL LAMDA U+1D6CC but font support is often lacking, and it looks like Unicode categorizes *that* also as a lowercase letter. If you can convince the Unicode Consortium to add a lambda that is of class symbol, Haskell can then make use of it — once there are fonts that support it. There is http://www.stixfonts.org/ For typesetting with Xe[La]TeX or Lua[La]TeX, use XITS (in the TeXLive package). (And then we'll have to deal with folks trying to use the letter, because everyone knows the Roman alphabet is the only one that matters and of *course* Greek letters are symbol characters Pfeh.) This is the big problem right now: how to enter these symbols efficiently. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] If you'd design a Haskell-like language, what would you do different?
On 21 Dec 2011, at 04:27, Ashok Gautham wrote: On Tue, Dec 20, 2011 at 11:17:32PM +0100, Hans Aberg wrote: The monospace characters U+1D670-1D6A3 might be used for keywords. Font: http://www.stixfonts.org/ I feel that monospace fonts should be used for all of programming. A language could use Unicode symbols, but if it enforces typography, it is destined to win an award for being really unusable I have some books from the 1980s which does not use monospace; it seems to be a later movement. Using it for all symbols would be awkward. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] If you'd design a Haskell-like language, what would you do different?
On 21 Dec 2011, at 11:03, Brandon Allbery wrote: On Wed, Dec 21, 2011 at 04:51, Hans Aberg haber...@telia.com wrote: The one on the list is not a mathematical symbol. It should be ⋆ STAR OPERATOR U+22C6 or ∗ ASTERISK OPERATOR U+2217. ...except, at least in my current font, the former is microscopic and the latter not a whole lot better. The advantage of the one they chose is it's big and readable. (That's part of why I assume it's intended for kinds, actually.) This problem is in my editor for unstyled text due to that if it a symbol is not available in the font selected, it just chooses a glyph from the next font available in alphabetical order. Hopefully such problem will be resolved in the future. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] If you'd design a Haskell-like language, what would you do different?
On 21 Dec 2011, at 11:09, Jesse Schalken wrote: IIRC, Scite's default configuration is with non-monospace font. I actually found it quite appealing, and in fact forgot about it entirely after some usage. It is much easier on the eyes to read. The difference is really whether you care about aligning things mid-line or not, not to mention editor support (i.e. not Vim or other terminal-based editor). Right, ASCII code that relies on monospace for such midline alignments can be quite unreadable, but otherwise it has nothing really to contribute. Non-monospace might in fact be more readable, taking away the fact that it may take some time to get used to it, since monospace has been used so much. For such alignments, one would either to write to code so it does not depend on it, or find some other means to do it. Hans On Wed, Dec 21, 2011 at 8:58 PM, Hans Aberg haber...@telia.com wrote: On 21 Dec 2011, at 04:27, Ashok Gautham wrote: On Tue, Dec 20, 2011 at 11:17:32PM +0100, Hans Aberg wrote: The monospace characters U+1D670-1D6A3 might be used for keywords. Font: http://www.stixfonts.org/ I feel that monospace fonts should be used for all of programming. A language could use Unicode symbols, but if it enforces typography, it is destined to win an award for being really unusable I have some books from the 1980s which does not use monospace; it seems to be a later movement. Using it for all symbols would be awkward. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] If you'd design a Haskell-like language, what would you do different?
On 21 Dec 2011, at 11:22, Andrew Coppin wrote: On 21/12/2011 10:09 AM, Jesse Schalken wrote: IIRC, Scite's default configuration is with non-monospace font. I actually found it quite appealing, and in fact forgot about it entirely after some usage. It is much easier on the eyes to read. The difference is really whether you care about aligning things mid-line or not, not to mention editor support (i.e. not Vim or other terminal-based editor). SciTE's default binding /is/ proportional, not mono-space. I find it ever so irritating. Then again, I'm sure this one comes squarely down to personal preference, so it seems pointless to debate it. LaTeX offers the possibility of mid-line alignment even if you don't use monospace - a feature which I haven't seen in any other text processing system. It's a pitty this isn't more widespread... Monospace isn't used in math (except in the days when one used typewriters), but alignments are of course used in matrices and multiline formulas, for example, which may correspond to uses in computer code. A problem is that LaTeX is used for rendering typeset pages, and not really suitable for writing direct computer code, though Unicode characters can improve the readability of LaTeX source code. The link below shows an example. Hans http://www.charlietanksley.net/philtex/the-unicode-math-package-for-xelatex-and-the-stix-fonts/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] If you'd design a Haskell-like language, what would you do different?
On 20 Dec 2011, at 22:51, Chris Wong wrote: One thing that concerns me is the use of capital letters to distinguish type and class names and constructors from values. If I was doing it over I would use a typographical distinction like italics for types, bold for classes. That way we could have a constructor named ∅, a function named ∈, a class named ℝ. It's Algol all over again! Will we have to typeset our keywords in bold too? There are in fact Unicode symbols for that, see http://unicode.org/charts/PDF/U1D400.pdf The monospace characters U+1D670-1D6A3 might be used for keywords. Font: http://www.stixfonts.org/ Not hard to add. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A Mascot
On 16 Nov 2011, at 05:18, John Meacham wrote: People tend to concentrate on the lambda which cooresponds to the functional aspect of haskell when designing logos. Not nearly enough attention is paid to the other striking feature, the laziness. The 'bottom' symbol _|_ should feature prominently. The two most defining features of haskell are that it is purely functional and _|_ inhabits every type. The combination of which is very powerful. The mascot already represents the lambda, so all that is needed is to show off its _|_. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A Mascot
On 16 Nov 2011, at 23:49, heathmatlock wrote: I took Jerzy's suggestions into consideration and made the lamb skinnier, maybe it looks less like a penguin now. http://imgur.com/4oeJz A formula that is Haskell specific is \x - ⊥ ≠ ⊥ It is mentioned in the Haskell 98 Report, sec. 6.2, Strict Evaluation, p. 82. The LHS and RHS are different, because they can be distinguished by seq. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda Calculus: Bound and Free formal definitions
On 30 Dec 2010, at 03:05, Mark Spezzano wrote: ... regarding formal definitions of FREE and BOUND variables he gives Defn 5.2 as It is the occurrence of a variable that is free or bound. An occurrence of a variable is bound if it is in the scope of something that binds it; otherwise it is free. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Hugs Haskore loading
When trying to load Haskore in Hugs Sept 2006 (say by :l), it does not work because it is in a subdirectory Haskore/Src/, despite that the Hugs searchpath includes /usr/local/lib/hugs/packages/* I could of course change this searchpath, but I'm curios about how to fix it without it - it seems to work for a lot of other packages. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hugs Haskore loading
On 21 Aug 2010, at 20:24, Henning Thielemann wrote: When trying to load Haskore in Hugs Sept 2006 (say by :l), it does not work because it is in a subdirectory Haskore/Src/, despite that the Hugs searchpath includes /usr/local/lib/hugs/packages/* I could of course change this searchpath, but I'm curios about how to fix it without it - it seems to work for a lot of other packages. Did you install Haskore with Cabal or is it a version of Haskore that is shipped with Hugs? It is the version that comes with Hugs. It is the same as listed on http://haskell.org/haskore/ . What other version do you have in mind. The -P option can be used to extend the search path. Yes, but as said above, I wondered what was needed to fix the package. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hugs Haskore loading
On 21 Aug 2010, at 20:24, Henning Thielemann wrote: When trying to load Haskore in Hugs Sept 2006 (say by :l), it does not work because it is in a subdirectory Haskore/Src/, despite that the Hugs searchpath includes /usr/local/lib/hugs/packages/* I could of course change this searchpath, but I'm curios about how to fix it without it - it seems to work for a lot of other packages. Did you install Haskore with Cabal or is it a version of Haskore that is shipped with Hugs? The -P option can be used to extend the search path. I think the problem is that Haskore is written for an older version of Hugs that just searches all subdirectories without extra requirements, but in the current version, a module Foo in Haskore/Src must be named Src.Foo. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hugs Haskore loading
On 21 Aug 2010, at 20:57, Henning Thielemann wrote: Did you install Haskore with Cabal or is it a version of Haskore that is shipped with Hugs? It is the version that comes with Hugs. It is the same as listed on http://haskell.org/haskore/ . What other version do you have in mind. There is Paul Hudak's original version as Cabal package http://hackage.haskell.org/package/haskore-vintage I just put the directory src/ in this package and replaced it with Haskore/ in the Hugs distribution, and then it loaded. and one that I have messed http://hackage.haskell.org/package/haskore What changes have you made? - perhaps the packages should be unified. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hugs Haskore loading
On 21 Aug 2010, at 20:57, Henning Thielemann wrote: Did you install Haskore with Cabal or is it a version of Haskore that is shipped with Hugs? It is the version that comes with Hugs. It is the same as listed on http://haskell.org/haskore/ . What other version do you have in mind. There is Paul Hudak's original version as Cabal package http://hackage.haskell.org/package/haskore-vintage and one that I have messed http://hackage.haskell.org/package/haskore I see now that the original Haskore page http://haskell.org/haskore/ has been replaced without linking by http://www.haskell.org/haskellwiki/Haskore . So just make a forward link there, I think. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hugs Haskore loading
On 21 Aug 2010, at 21:51, Henning Thielemann wrote: and one that I have messed http://hackage.haskell.org/package/haskore What changes have you made? - perhaps the packages should be unified. I changed almost everything: Divided modules, designed a hierarchy for module names, generalized many functions and types. In retrospective I should have given it a distinct name. If the basic functionality is the essentially the same, it is probably better to have a single, large package, where people can add their own stuff modularly, though it is good to have a license that admits independent cloning for those that so wish. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc in macports
On 12 Aug 2010, at 12:49, Benedict Eastaugh wrote: On 11 August 2010 15:49, Ozgur Akgun ozgurak...@gmail.com wrote: Personally, I'd like to use the macports version, if the ghc version there was resonably recent (having 2 versions, a stable and an edge could be a good idea?) You could use Homebrew instead. That has a fairly up-to-date version of GHC and the Haskell Platform. http://mxcl.github.com/homebrew/ On http://wiki.github.com/mxcl/homebrew/installation it says: delete /usr/local/include and/usr/local/lib So its not for those that also installs standard distributions, it seems. But what's wrong with the binaries listed here: http://haskell.org/ghc/ Fairly easy to install. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc in macports
On 12 Aug 2010, at 14:08, Ozgur Akgun wrote: On http://wiki.github.com/mxcl/homebrew/installation it says: delete /usr/local/include and/usr/local/lib So its not for those that also installs standard distributions, it seems. I thought this was just a recommendation. It also says: We’ve had a *lot* of bug reports that are first inexplicable and later it turns out that it’s because the user has some of their own libs and headers in/usr/local. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc in macports
On 12 Aug 2010, at 20:46, Gaius Hammond wrote: its not for those that also installs standard distributions, it seems. But what's wrong with the binaries listed here: http://haskell.org/ghc/ Fairly easy to install. Yes and no; on OSX 10.5.8 it works better to install GHC from the binary then build Platform yourself. On 10.6 it seems to be OK. OK. I was only thinking on the compiler (as in the first post). When adding packages, it is trickier; I've only by hand. Then in some case MacPorts might be better if wanting to do a lot of package chasing - perhaps it was Gtk. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] lambdacats
On 6 Aug 2010, at 09:48, Andrew Coppin wrote: Hello, does anyone happen to have the lambdacats page cached? The domain (arcanux.org http://arcanux.org) and server have disappeared and the wayback machine doesn't have the images. Somebody else noticed, eh? Good thing I grabbed most of the actually amusing images before it vanished. Still, that site was hardly ever updated anyway. And it's not like you need a special website just to stick broken English on pictures of cats... Search by an actual image can be done at http://www.tineye.com/. This is useful if one wants to find an original, or see its original context. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Suggestions For An Intro To Monads Talk.
On 3 Aug 2010, at 23:51, aditya siram wrote: I am doing an Intro To Monads talk in September [1]. The audience consists of experienced non-Haskell developers but they will be familiar with basic functional concepts (closures, first-class functions etc.). I am looking for suggestions on how to introduce the concept and its implications. I'd also like to include a section on why monads exist and why we don't really see them outside of Haskell. Probably because one does not bother writing them out in the type system. I wrote on a C++ wrap for Guile, and they showed up when typing expressions, though C++ templates are too limited to make this efficiently. The monad has a code lifting property. If one has code which has both non-monadic and monadic components, it can be lifted up to the monadic level without having iterates (can be taken away with the monad projection). So if one has code which has both non-IO and IO components, it can be lifted to the becoming all IO. Since IO and other imperative structures are incompatible with the lazy evaluation default, the type system can be used to describe them using monads. Then one can use syntactic sugar like do and = to make the code look like ordinary imperative code. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Category Theory woes
On 19 Feb 2010, at 00:52, Richard O'Keefe wrote: Turning to the Wikipedia article, we find The word kangaroo derives from the Guugu Yimidhirr word gangurru, referring to a grey kangaroo Thanks, particularly for giving the name of the native language. Hope the Wikipedia article can be trusted. :-) It's time this urban legend was forgotten. Not at all, there are sites specializing in such http://www.snopes.com/ http://www.snopes.com/inboxer/hoaxes/computer.asp Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Category Theory woes
On 19 Feb 2010, at 00:05, Nick Rudnick wrote: Mathematicians though stick to their own concepts and definitions individually. For example, I had conversations with one who calls monads triads, and then one has to cope with that. Yes. But isn't it also an enrichment by some way? Yes, one must be able to choose notation that fits with the notions. A similar situation exists in the case of computer languages, having their own syntax. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Category Theory woes
On 19 Feb 2010, at 00:55, Daniel Fischer wrote: I'd always assumed ring was generalised from Z[n]. As in cyclic group, arrange the numbers in a ring like on a clockface? Maybe. As far as I know, the term ring (in the mathematical sense) first appears in chapter 9 - Die Zahlringe des Körpers - of Hilbert's Die Theorie der algebraischen Zahlkörper. Unfortunately, Hilbert gives no hint why he chose that name (Dedekind, who coined the term Körper, called these structures Ordnung [order]). The Wikipedia article Ring says he used it for a specific one where the elements somehow cycled back. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Category Theory woes
On 19 Feb 2010, at 12:12, Daniel Fischer wrote: ...As far as I know, the term ring (in the mathematical sense) first appears in chapter 9 - Die Zahlringe des Körpers - of Hilbert's Die Theorie der algebraischen Zahlkörper. Unfortunately, Hilbert gives no hint why he chose that name (Dedekind, who coined the term Körper, called these structures Ordnung [order]). The Wikipedia article Ring says he used it for a specific one where the elements somehow cycled back. Yes. And I deem a) the english wikipedia a more reliable source of information [concerning things mathematical] than the german, b) Harvey Cohn more trustworthy than either wikipedia. But a quick look at Hilbert's paper didn't reveal the property Cohn mentioned (according to wp) and no explanation of Hilbert why he chose the term. So I remain in doubt. The term group was introduced Évariste Galois, though he meant what we call a cancellative monoid, but since they are finite, have inverses. So perhaps Hilbert made play on that word: a group is a small number of people, a ring larger, like a gang. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Category Theory woes
On 18 Feb 2010, at 14:48, Nick Rudnick wrote: * the definition of open/closed sets in topology with the boundary elements of a closed set to considerable extent regardable as facing to an «outside» (so that reversing these terms could even appear more intuitive, or «bordered» instead of closed and «unbordered» instead of open), I take closed as coming from being closed under limit operations - the origin from analysis. A closure operation c is defined by the property c(c(x)) = c(x). If one takes c(X) = the set of limit points of X, then it is the smallest closed set under this operation. The closed sets X are those that satisfy c(X) = X. Naming the complements of the closed sets open might have been introduced as an opposite of closed. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Category Theory woes
On 18 Feb 2010, at 20:20, Daniel Fischer wrote: + definition backtracking: «A closure operation c is defined by the property c(c(x)) = c(x). Actually, that's incomplete, ... That's right, it is just the idempotency relation. ...missing are - c(x) contains x - c(x) is minimal among the sets containing x with y = c(y). It suffices*) with a lattice L with relation = (inclusion in the case of sets) satifying i. x = y implies c(x) = c(y) ii. x = c(x) for all x in L. iii. c(c(x)) = x. Hans *) The definition in a book on lattice theory by Balbes Dwinger. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Category Theory woes
On 18 Feb 2010, at 19:19, Nick Rudnick wrote: agreed, but, in my eyes, you directly point to the problem: * doesn't this just delegate the problem to the topic of limit operations, i.e., in how far is the term «closed» here more perspicuous? * that's (for a very simple concept) the way that maths prescribes: + historical background: «I take closed as coming from being closed under limit operations - the origin from analysis.» + definition backtracking: «A closure operation c is defined by the property c(c(x)) = c(x). If one takes c(X) = the set of limit points of X, then it is the smallest closed set under this operation. The closed sets X are those that satisfy c(X) = X. Naming the complements of the closed sets open might have been introduced as an opposite of closed.» 418 bytes in my file system... how many in my brain...? Is it efficient, inevitable? Yes, it is efficient conceptually. The idea of closed sets let to topology, and in combination with abstractions of differential geometry led to cohomology theory which needed category theory solving problems in number theory, used in a computer language called Haskell using a feature called Currying, named after a logician and mathematician, though only one person. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Category Theory woes
On 18 Feb 2010, at 22:06, Daniel Fischer wrote: ...missing are - c(x) contains x - c(x) is minimal among the sets containing x with y = c(y). It suffices*) with a lattice L with relation = (inclusion in the case of sets) satifying i. x = y implies c(x) = c(y) ii. x = c(x) for all x in L. iii. c(c(x)) = x. Typo, iii. c(c(x)) = c(x), of course. Sure. If we replace set by lattice element and contains by =, the definitions are equivalent. Right. The one you quoted is better, though. It is a powerful concept. I think of a function closure as what one gets when adding all an expression binds to, though I'm not sure that is why it is called a closure. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Category Theory woes
On 18 Feb 2010, at 23:02, Nick Rudnick wrote: 418 bytes in my file system... how many in my brain...? Is it efficient, inevitable? Yes, it is efficient conceptually. The idea of closed sets let to topology, and in combination with abstractions of differential geometry led to cohomology theory which needed category theory solving problems in number theory, used in a computer language called Haskell using a feature called Currying, named after a logician and mathematician, though only one person. It is SUCCESSFUL, NO MATTER... :-) But I spoke about efficiency, in the Pareto sense (http://en.wikipedia.org/wiki/Pareto_efficiency )... Can we say that the way in which things are done now cannot be improved?? Hans, you were the most specific response to my actual intention -- could I clear up the reference thing for you? That seems to be an economic theory version of utilitarianism - the problem is that when dealing with concepts there may be no optimizing function to agree upon. There is an Occam's razor one may try to apply in the case of axiomatic systems, but one then finds it may be more practical with one that is not minimal. As for the naming problem, it is more of a linguistic problem: the names were somehow handed by tradition, and it may be difficult to change them. For example, there is a rumor that kangaroo means I do not understand in a native language; assuming this to be true, it might be difficult to change it. Mathematicians though stick to their own concepts and definitions individually. For example, I had conversations with one who calls monads triads, and then one has to cope with that. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] multMM :: Matrix - Matrix - Matrix --multiplies two matrices question (Homework)
On 3 Feb 2010, at 07:38, 조광래 wrote: hi i was trying to solve it but All i got is type Matrix=[[Double]] multMM :: Matrix - Matrix - Matrix --multiplies two matrices multMM m t =[[sum (zipWith (*) (head m)(a)) ] ]where a = [head a | a- t] Main multMM [[2,1,-6],[1,-3,2]] [[1,0,-3],[0,4,20],[-2,1,1]] [[14.0]] from this i could get only the first multiplication 14that is by 2*1 + 1*0 + -6*-2 = 14 how can i make this go throw all rows and colums to get multiple of matrixs? Perhaps you might try the beginners mailing list: http://haskell.org/haskellwiki/Mailing_lists http://haskell.org/mailman/listinfo/beginners because here, people will just assume one wants effective solutions. :-) Anyway, the page I mentioned before has a matrix multiplication: http://haskell.org/haskellwiki/Prelude_extensions It uses the function transpose(), which is in the module Data.List. I find looking into the modules of Hugs useful, on my computer they are in /usr/local/lib/hugs/packages but those for GHC are also available online: http://www.haskell.org/ghc/docs/latest/html/libraries/ Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Very imperfect hash function
On 2 Feb 2010, at 03:05, Richard O'Keefe wrote: A simple hash-function for strings is to simply exclusive-or the bytes and then reduce modulo a prime number, Simply exclusive-oring the bytes will give you at most 256 distinct results. (For an ASCII source, 128 distinct results.) After that, there hardly seems to be any point in reduction modulo a prime. Right - I just gave an example of how simple hash functions may be created. The original question deals with Int32s, not strings. As already mentioned before, there are more advance libraries here http://en.wikipedia.org/wiki/Perfect_hash_function but they are not written in Haskell. So you have to rewrite them or use the FFI. This approach can't tell a CAT from an ACT or a DOG from a GOD, which is another strike against it. (It also can't tell a TITTLE from a TILE, or a BOTTLE from a BOLE, for obvious reasons.) The hash function just tries to produce random lookup values, which are used to flatten the average depth of the lookup table at the entries of the array. So there is a tradeoff between a fast hash function, and one that does a good job. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] matrix question
On 2 Feb 2010, at 13:15, 조광래 wrote: define functions type Matrix=[[Double]] multMM :: Matrix - Matrix - Matrix --multiplies two matrices det :: Matrix - Double --computes the determinant of a matrix inv :: Matrix - Matrix --inverts a matrix i stuck on those problems can any one help me out? Plug in the word matrix on http://haskell.org/; then there comes up matches Prelude extensions which has that type. There is also a Numeric Prelude. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] OT: Literature on translation of lambda calculus to combinators
On 28 Jan 2010, at 10:54, Dušan Kolář wrote: Could anyone provide a link to some paper/book (electronic version of both preferred, even if not free) that describes an algorithm of translation of untyped lambda calculus expression to a set of combinators? Preferably SKI or BCKW. I'm either feeding google with wrong question or there is no link available now... Here is a paper that uses that standard arithmetic operators that Church defined: http://www.dcs.ed.ac.uk/home/pgh/amen.ps Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Very imperfect hash function
On 31 Jan 2010, at 20:07, John Lato wrote: Or are you suggesting an actual hash table? The hash function folds the keys onto an interval. Since you have Int values k, you might just use a mod k n function for that. If it's the latter, I'm not certain where the array fits into the picture. I'm pretty sure I'm missing something here. There is a module Data.HashTable. The array is just to make lookup fast. Like in: ST s (STArray s HashKey (Map Key Value)) I was misunderstanding your intention here. This is an interesting approach, but I would still try an IntMap first. A simple hash-function for strings is to simply exclusive-or the bytes and then reduce modulo a prime number, which will be the table size. The average lookup time complexity is the one of the hash table. You can then compare with the IntMap, which may have time complexity O(4), the number of bytes in an Int32. There might be a big difference in the constant factor, though: an array seems to be much faster. I first made multivariate polynomial division using lists, because it is easy to work with, and an example of some stuff built on top took tens of seconds to run in Hugs. When reworking it using STArray (mutable) and Array (immutable), it has no noticeable delay. Though I am using Map and Set, too, the choice of container seems otherwise be dictated by what is most convenient to program. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Strange random choice algorithm
On 30 Jan 2010, at 20:59, michael rice wrote: I'm not sure where I got this PICK function from, and don't understand why it's written as it is, so I wanted to test it for randomness. It seems random enough. But if I understand the algorithm correctly, instead of selecting one of the elements from the list, it eliminates all the elements but one and that's the value it returns. Seems like a roundabout way of doing it. Comments? Below is a function draw() that shuffles an interval, and prints it out. Hans import Random getRandomIndex :: [a] - IO(Int) getRandomIndex ls = getStdRandom(randomR(0, (length ls) - 1)) remove:: Int - [a] - [a] remove 0 (x:xs) = xs remove n (x:xs) | n0 = x: remove (n-1) xs remove _ (_:_)= error remove: negative argument remove _ [] = error remove: too large argument shuffle :: [a] - IO [a] shuffle [] = return [] shuffle ls = do i - getRandomIndex ls do l - shuffle (remove i ls) return ((ls !! i) : l) draw ls = do k - shuffle ls putStr (show k) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Very imperfect hash function
On 29 Jan 2010, at 12:52, John Lato wrote: There are minimal perfect hash functions; there are some libraries mentioned here, though they are not in Haskell code: http://en.wikipedia.org/wiki/Perfect_hash_function This is suitable when you do a lot of lookups with few key updates. An alternative might be Data.Map, where lookups have time complexity O(log n), n = size of map. The minimal perfect hash function looks like the real algorithmic solution, but I would just use Data.IntMap for this. That looks interesting too. Yet another idea: use arrays http://haskell.org/haskellwiki/Arrays Then build a hash table, say just taking mod k n, and have values in some lookup map. If n set of keys, average time complexity is O(1), and arrays should be very fast. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Very imperfect hash function
On 29 Jan 2010, at 15:57, John Lato wrote: That looks interesting too. Yet another idea: use arrays http://haskell.org/haskellwiki/Arrays Then build a hash table, say just taking mod k n, and have values in some lookup map. If n set of keys, average time complexity is O(1), and arrays should be very fast. I just want to be sure I understand this. For this plan, you aren't intending to use a perfect hash function at all, correct? Yes, this is another idea. In a hash table, it is not important to have different indices, only that that table entries are as flat as possible. Are you basically just suggesting to stick everything in an array with the key as an index? You still need to fold the key values onto some interval. Or are you suggesting an actual hash table? The hash function folds the keys onto an interval. Since you have Int values k, you might just use a mod k n function for that. If it's the latter, I'm not certain where the array fits into the picture. I'm pretty sure I'm missing something here. There is a module Data.HashTable. The array is just to make lookup fast. Like in: ST s (STArray s HashKey (Map Key Value)) In either case, I don't think this would be as good as what I thought was your original suggestion, i.e. using a minimal perfect hash function mphf that hashes keys to a value 0..v-1. With v=number of values, valArr = array of all values, then lookup k = valArr ! mphf k Right, but you may have to avoid implementing the perfect hash function by yourself, if it is only available in C. :-) There is a FFI, though. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Map unionWith generalization
On 28 Jan 2010, at 03:09, Twan van Laarhoven wrote: For example, in Map String Integer (sparse representation of monomials) compute the minimum value of all associative pairs with the same key (the gcd); if only one key is present, the absent should be treated as having value 0. So unionWith min xs ys will not work, because unionWith will always apply the identity to the remaining value when one key is missing, whereas it should be sent to 0. If missing keys represent 0, then wouldn't this work? intersectionWith min xs ys Yes, that works for the gcd function using min. Thank you - this function is used a lot, so it is good to have it simple. For the general problem, one still needs a better interface. For (-), though missing keys represent 0, if the first is missing, the second should be negated. And if both are present, one should filter out keys with 0 value. Right now, this is a combination of negate, (+), and filter (/= 0). Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Very imperfect hash function
On 28 Jan 2010, at 20:07, Steve Schafer wrote: The data are currently in a large lookup table. To save space, I'd like to convert that into a sort of hash function: hash :: key - value My question is this: Is there any kind of generic approach that can make use of the knowledge about the internal redundancy of the keys to come up with an efficient function? There are minimal perfect hash functions; there are some libraries mentioned here, though they are not in Haskell code: http://en.wikipedia.org/wiki/Perfect_hash_function This is suitable when you do a lot of lookups with few key updates. An alternative might be Data.Map, where lookups have time complexity O(log n), n = size of map. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Map unionWith generalization
I need ideally some generalizations of unionWith and unionWithKey, for efficiency matters (i.e. avoiding conversions and traversing the maps more than once). I could use a modification of the code in Map.hs, but then the problem is that the module Map interface does not export the constructors of data Map. So suggestions are welcome. For example, in Map String Integer (sparse representation of monomials) compute the minimum value of all associative pairs with the same key (the gcd); if only one key is present, the absent should be treated as having value 0. So unionWith min xs ys will not work, because unionWith will always apply the identity to the remaining value when one key is missing, whereas it should be sent to 0. So here, one would want: (a - c) - (b - c) - (a - b - c) - Map k a - Map k b - Map k c where the two first functions are applied when the first or second key is missing. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Map unionWith generalization
On 27 Jan 2010, at 14:56, Jan-Willem Maessen wrote: So here, one would want: (a - c) - (b - c) - (a - b - c) - Map k a - Map k b - Map k c where the two first functions are applied when the first or second key is missing. Ah, the swiss army knife function on maps. This particular formulation works well for the application you describe above, where you're completely traversing both maps. The following really grubby variant can be used to implement asymptotically efficient variations of union, intersection, difference, etc., etc: swissArmy :: (Map k a - Map k c) --- Used to process submaps unique to the left map (Map k b - Map k c) --- Used to process submaps unique to the right map (a - b - Maybe c) - -- Used to process a single common entry Map k a - Map k b - Map k c I'm not sure why you want to throw in functions between maps in the two first arguments. Then there is no requirement that single keys are preserved. But it is a good idea to have a Maybe so that one can remove keys on the fly. Then your function appears to be: -- helper just2 :: (a - b - c) - a - b - Maybe c just2 f a b = Just (f a b) swissArmy (fmap (const 0)) (fmap (const 0)) (just2 gcd) Here are unionWith and intersectionWith: unionWith f = swissArmy id id (just2 f) intersectionWith = swissArmy (const empty) (const empty) (just2 f) differenceWith = swissArmy id (const empty) (\a b - Nothing) When throwing together tree-like data structures, I often start by writing this function; it handles most of the bulk operations I might want to do as one-liners. It's got a messy, ugly type signature, but it does everything you want as efficiently as you want.* My guess is that is when you write things from scratch. I wanted to add these function on top of the module Data.Map, but then that seems not to be possible, as the constructors are not exported. I could make a copy of this file, and then make my own variation. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Map unionWith generalization
On 27 Jan 2010, at 16:33, Jan-Willem Maessen wrote: I'm not sure why you want to throw in functions between maps in the two first arguments. Then there is no requirement that single keys are preserved. But it is a good idea to have a Maybe so that one can remove keys on the fly. A good point. Technically, one should delimit the scope of the first two arguments: data KeyPreservingMapOperation k a b = AlwaysEmpty | Identity | MapMaybeWithKey (k - a - Maybe b) perform :: KeyPreservingMapOperation a b - Map k a - Map k b perform AlwaysEmpty = const empty perform Identity = id perform (MapMaybeWithKey f) = mapMaybeWithKey f I'm thinking about (k - Maybe a - Maybe b - Maybe c) - Map k a - Map k b - Map k c The first two Maybe's tell if the keys are present, the last if one wants it in the resulting map. When throwing together tree-like data structures, I often start by writing this function; it handles most of the bulk operations I might want to do as one-liners. It's got a messy, ugly type signature, but it does everything you want as efficiently as you want.* My guess is that is when you write things from scratch. Yes. On the other hand, I've repeatedly run into the same problem you're describing: a api that doesn't give me an efficient way to perform an operation I know to be very simple. If every map provided an operation like this one, then I can avoid writing my own library from scratch when I need it --- especially when from scratch means fork the code and add what I need. So, library implementors: think hard about your swiss army knife combinators. You end up with messy functions with gigantic signatures. On the other hand, you can often add a couple of judicious INLINE annotations and remove tons of code from the rest of your library. Then expose them, and mark them as the functions of last resort that they truly are. One can transverse the product of keys. Then I'm thinking about (k1 - k2 - a - b - Maybe c - Maybe(k, c)) - Map k1 a - Map k2 b - Map k c The first Maybe tells if the key is already present; the second if one wants it inserted. The idea in both cases is to combine the modifying functions into one. This simplifies the interface. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Map unionWith generalization
On 27 Jan 2010, at 21:29, Jan-Willem Maessen wrote: I'm thinking about (k - Maybe a - Maybe b - Maybe c) - Map k a - Map k b - Map k c The first two Maybe's tell if the keys are present, the last if one wants it in the resulting map. That has the same behavior semantically, but it's no more efficient than performing a unionWith followed by a filter. It would not be the complexity, but the constant factor, by not having to transverse it twice. I'm not sure how it works in a functional language, and the trees must be rebalanced, too. For example, consider implementing: xs `intersection` singleton k v in this way. With the function given, the complexity is necessarily O(size xs): we must traverse every key/value pair in xs. By contrast, by aggregating the operations on keys that exist only in a single map, we can write functions like intersection with the desired complexity (which is O(log (size xs)) in this case). That is a good point. One can transverse the product of keys. Then I'm thinking about (k1 - k2 - a - b - Maybe c - Maybe(k, c)) - Map k1 a - Map k2 b - Map k c The first Maybe tells if the key is already present; the second if one wants it inserted. Traversing cross products is a very different operation from zipping in the key space. Again I wouldn't want to mistakenly substitute one for the other! For the first one, think of sums of sparse matrices or polynomials, and the second, products. But in this case I think you'll find that you're already well served by the functions that already exist---adding this function doesn't enable you to do anything more efficiently (at least in a big-O sense). Yes, I can't implements (-) directly; it must be a combination of (+) and negate, and the 0 must be filtered out in an extra pass. And for gcd of monomials, it is now a combination of lcm, (*) and (/), instead of a single pass. Unfortunately, these operations are used a lot, so getting a smaller constant factor is important. The idea in both cases is to combine the modifying functions into one. This simplifies the interface. Understood, and with a sufficiently smart compiler we might analyze the behavior of the function and do the right thing with the single- function interface in both cases. I have yet to encounter a compiler that is both smart and reliable on this count. That is why I've found it necessary to expose these kinds of functions. By your example above, there may be a conflict between a general, simple interface, and implementing things like intersections. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parse error
On 17 Jan 2010, at 11:44, Andrew Coppin wrote: Urg, but that's *ugly*. Is there no way I can reduce the amount of indentation to something more reasonable? main = do putStrLn Line 1 putStrLn Line 2 let xs = do x - [1..10] y - [1..10] return (x+y) print xs That better? It's an improvement. It's still not pretty, but I guess that's as good as it's going to get... Maybe this is an instance of Haskell trying to tell me if you need to write a 20-line do-block in the middle of your function, you're doing it wrong. Haskell starts the new indentation level where the following lexeme is (Haskell-98 Report, sec. 2.7). So to reduce indentation, one must start a new line (already mentioned in this thread). This works in Hugs: main = do putStrLn Line 1 putStrLn Line 2 let xs = do x - [1..10] y - [1..10] return (x+y) print xs The xs on a new line looks a bit unusual, and it takes a bit more vertical space, but one gets nice indentation levels. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] help with musical data structures
On 15 Nov 2009, at 12:55, Stephen Tetley wrote: http://hackage.haskell.org/packages/archive/haskore/0.1/doc/html/Haskore-Basic-Pitch.html but maybe it is not what you need, since it distinguishes between C sharp and D flat and so on. The enharmonic doublings and existing Ord instance make Haskore's PitchClass a tricky proposition for representing the Serialist's view of pitch classes. An integer (or Z12) represent would be simpler. A Z12 representation is really only suitable for serial music, which in effect uses 12 scale degrees per octave. To get pitch names I would recover them with a post-processing step, spelling pitches with respect to a scale (here a SpellingMap): spell :: SpellingMap - Pitch - Pitch The spell function returns the note in the scale (SpellingMap) if present, otherwise it returns the original to be printed with an accidental. I have my own pitch representation, but a SpellingMap for Haskore would be type SpellingMap = Data.Map PitchClass PitchClass Scales here are functions that generate SpellingMaps rather than objects themselves. The modes and major and minor scales have easy generation as they are someways rotational over the circle of fifths (I've have implemented a useful algorithm for this but can't readily describe it[1]). Hijaz and klezmer fans need to construct their spelling maps by hand. The pitch and notation systems that Western music uses can be described as generated by a minor second m and major second M. Sharps and flats alter with the interval M - m. If departing from two independent intervals, like a perfect fifth and the octave, then m and M can be computed. - I have written some code for ChucK which does that and makes them playable on the (typing) keyboard in a two- dimensional layout. The pitch system, which I call a diatonic pitch system, is then the set of combinations p m + q M, where p, q are integers (relative a tuning frequency). The sum d = p + q acts a scale degree of the pitch system. Sharps and flats do not alter this scale degree. Typical common 7 note scales have adjacent scale degrees. This is also true for scales like hijaz. The note name can then be computed as follows: First one needs (p, q) values representing the note names a b c d e f g having scale degrees 0, ..., 6, plus a value for the octave. If given an arbitrary combination (p, q), first reduce its octave, and then compute its scale degree; subtract the (p, q) value of the note name with the same scale degree. There results a note with p + q = 0, i.e., p = - q. If q 0, it is is the number of sharps, if p 0 it is the number of flats. This method can be generalized. It is not necessary to have 7 notes per diapason, and the diapason need not be the octave. By adding neutral seconds, one can describe more general pitch systems (one is enough for Arab, Persian and Turkish scales). Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Pattern matching does not work like this?
On 15 Jul 2009, at 12:25, Eugene Kirpichov wrote: If ++ could be pattern matched, what should have been the result of let (x++y)=[1,2,3] in (x,y)? It will branch. In terms of unification, you get a list of substitutions. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Pattern matching does not work like this?
On 15 Jul 2009, at 13:22, Luke Palmer wrote: If ++ could be pattern matched, what should have been the result of let (x++y)=[1,2,3] in (x,y)? It will branch. In terms of unification, you get a list of substitutions. f :: [a] - ([a],[a]) f (x ++ y) = (x,y) For an argument s, any pair (x, y) satisfying s = x ++ y will match. That is, if s = [s_1, ..., s_k], the solutions j = 0, ..., k, x = [s_1, ..., s_j], y = [s_(j+1), ..., s_k]. And for each one, a potentially different value could given. That is, s could produce multiple values. If this pattern branches, it could hardly be considered a function which takes lists and returns pairs. It would have to return something else. So this would be a multi-valued function, which sometime is useful as a concept. But if the choices are indexed, they can be reduced to a single valued function. Like g(x,y) with the requirement that if x ++ y = x' ++ y', then g(x, y) = g(x', y'). This branching is what would happen if one tries to make a type theory based on sets. (It is possible to implement Horn clauses as unification branching.) The selection of branches correspond to a choice in the proof tree. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] gcd
On 2 May 2009, at 04:05, Steve wrote: Why is gcd 0 0 undefined? In math, one may define gcd(x, y) as a generator of the ideal generated by x and y in the ring of integers Z. The gcd(x, y) then always exists as the ring Z is a PID (principal ideal domain), i.e., all ideals can be generated by a single element, which can be proven using Euclid's algorithm, also useful for computing the gcd in Z. Anyway, the ideal generated by 0 and 0 is the zero ideal 0, which also is generated by the single generator 0. So gcd(0, 0) = 0 by this definition. In Z, one may take the gcd = 0, but that may not work in every PID. If k is a field, then the polynomial ring k[x] is a PID, but not the ring k[x_1, ..., x_n]. So that leads to Buchberger's Groebner Basis Algorithm. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Ease of Haskell development on OS X?
On 22 Mar 2009, at 10:28, Colin Adams wrote: OK, I got it installed, but build warned me of duplicate dylibs, and running my program gave a bus error. So I port uninstalled gtk2, so now it compiled without warnings, but the program won't run because I had been forced to uninstall pangoft to uninstall gtk2. So now I need to uninstall the gtk framework - how do I do that? Then i can re-install the macports version and have a working system again. You might move it out of the way: sudo mv /opt /opt1 and then move it back. To get rid of ports altogether, sudo rm -rf /opt (But be careful so you type right when removing as root, as errors can screw up the whole installation.) I looked up my records - I compiled gtk2hs, and as was remarked, the one in MacPorts (but not gtk2 alone) insists on installing its own GHC. When taking down the sources (external to MacPorts) of gtk2hs, the .tgz ones worked, but the sources from the archive caused some problems with autoconf - despite intense discussions also on the gtk2hs list, this problem was left unresolved. The libraries might cause problems when compiling, because even if a libpath is included in the compile, if there are system ones available, then may be used - a GCC quirk. So in such cases, one might have to edit the libpath so that the system libraries are not at all there, moving selected one out of the way, using libtools or something. This is very technical, though. Hans Aberg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Ease of Haskell development on OS X?
On 22 Mar 2009, at 11:32, Colin Adams wrote: creating build/temp.macosx-10.3-i386-2.5 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/opt/local/include -I/opt/local/Library/Frameworks/Python.framework/Versions/2.5/ include/python2.5 -c _hashopenssl.c -o build/temp.macosx-10.3-i386-2.5/_hashopenssl.o unable to execute -DNDEBUG: No such file or directory error: command '-DNDEBUG' failed with exit status 1 A search on the Apple site says it is a compile option used to remove assert(): http://developer.apple.com/documentation/Darwin/Reference/ManPages/man3/assert.3.html The first line mentions macosx-10.3 - do you have a compiler for an old system, or something? And I have a fairly recent python: $ python --version Python 2.5.1 $ which python /usr/bin/python Make sure to sign up (for free) as a developer at developer.apple.com and take down latest Xcode (mine is Version 3.1.2, though I do not know if it is the absolutely latest). Hans Aberg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Ease of Haskell development on OS X?
On 22 Mar 2009, at 12:45, Colin Adams wrote: No. It's all recent. And MacPorts installs its own gcc. Achim Scheider pointed out that the compiler name is missing, so the shell tries to execute '-DNDEBUG' as a program. When I try it, I get: $ sudo port install python_select Password: --- Fetching python_select --- Attempting to fetch select-0.2.1.tar.gz from http://arn.se.distfiles.macports.org/python_select --- Verifying checksum(s) for python_select --- Extracting python_select --- Configuring python_select --- Building python_select --- Staging python_select into destroot --- Installing python_select @0.2.1_0+darwin_9 --- Activating python_select @0.2.1_0+darwin_9 --- Cleaning python_select $ sudo python_select python25 Selecting version python25 for python Which perhaps only means that I already have it installed. But I also get this: $ which python /opt/local/bin/python $ python --version Python 2.5.1 $ /usr/bin/python --version Python 2.5.1 The version you tried to install is 2.5.2 - perhaps there is a script problem, then. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Ease of Haskell development on OS X?
On 22 Mar 2009, at 11:32, Colin Adams wrote: I tried issuing the sudo port install command on the wiki page. What did you try to install? ... After some time running it failed with: To fully complete your installation and make python 2.5 the default, please run sudo port install python_select sudo python_select python25 ...The thing is that when I removed python_select and python, there remains a $ /opt/local/bin/python --version Python 2.5.1 So your package somehow needs 2.5.2, which may be the culprit. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Ease of Haskell development on OS X?
On 22 Mar 2009, at 13:42, Colin Adams wrote: After some time running it failed with: To fully complete your installation and make python 2.5 the default, please run sudo port install python_select sudo python_select python25 ...The thing is that when I removed python_select and python, there remains a $ /opt/local/bin/python --version Python 2.5.1 So your package somehow needs 2.5.2, which may be the culprit. Which package? None of them are mine. One of the packages you tried to install asked for this, in this list: Just what it says on the wiki page: sudo port install glade3 libglade2 gstreamer gst-plugins-base gtksourceview cairo librsvg gtkglext firefox Looking into your post: --- Cleaning python25 --- Fetching py25-hashlib --- Attempting to fetch Python-2.5.2.tar.bz2 from http://www.python.org/ftp/python/2.5.2/ --- Verifying checksum(s) for py25-hashlib --- Extracting py25-hashlib --- Configuring py25-hashlib --- Building py25-hashlib with target build Error: Target org.macports.build returned: shell command cd it is py25-hashlib that is the culprit. I was able to install it. Then I got a later Python: --- Attempting to fetch Python-2.5.4.tar.bz2 from http://arn.se.distfiles.macports.org/python25 The procedure followed was (do a 'sudo -s' so save writing: First uninstall python25 and dependencies: # port uninstall python25 --- Unable to uninstall python25 2.5.2_5+darwin_8, the following ports depend on it: --- py25-gobject --- py25-numeric --- gstreamer # port uninstall gstrea...@0.10.19_0 --- Deactivating gstreamer @0.10.19_0 --- Uninstalling gstreamer @0.10.19_0 # port uninstall gstrea...@0.10.8_0 --- Uninstalling gstreamer @0.10.8_0 # port uninstall py25-gobject --- Deactivating py25-gobject @2.14.2_0 --- Uninstalling py25-gobject @2.14.2_0 # port uninstall py25-numeric --- Deactivating py25-numeric @24.2_1+macosx --- Uninstalling py25-numeric @24.2_1+macosx # sudo port uninstall python25 Then I noticed there was an unregistered python - those seems to confuse MacPorts. OS move it: # cd /opt/local/bin/ # mv python python1 Then I installed python_select and python25: # port install python_select --- Fetching python_select --- Verifying checksum(s) for python_select --- Extracting python_select --- Configuring python_select --- Building python_select --- Staging python_select into destroot --- Installing python_select @0.2.1_0+darwin_9 --- Activating python_select @0.2.1_0+darwin_9 --- Cleaning python_select bash-3.2# port install python25 --- Fetching python25 --- Attempting to fetch Python-2.5.4.tar.bz2 from http://arn.se.distfiles.macports.org/python25 --- Verifying checksum(s) for python25 --- Extracting python25 --- Applying patches to python25 --- Configuring python25 --- Building python25 --- Staging python25 into destroot --- Installing python25 @2.5.4_0+darwin_9+macosx --- Activating python25 @2.5.4_0+darwin_9+macosx To fully complete your installation and make python 2.5 the default, please run sudo port install python_select sudo python_select python25 --- Cleaning python25 After that follow the instructions: # sudo port install python_select Skipping org.macports.activate (python_select +darwin_9) since this port is already active --- Cleaning python_select # sudo python_select python25 Selecting version python25 for python And finally to py25-hashlib: # port install py25-hashlib Portfile changed since last build; discarding previous state. --- Fetching openssl --- Attempting to fetch openssl-0.9.8j.tar.gz from http://arn.se.distfiles.macports.org/openssl --- Verifying checksum(s) for openssl --- Extracting openssl --- Applying patches to openssl --- Configuring openssl --- Building openssl --- Staging openssl into destroot --- Installing openssl @0.9.8j_0 --- Activating openssl @0.9.8j_0 Error: Target org.macports.activate returned: Image error: /opt/local/ share/man/man3/bn_print.3.gz already exists and does not belong to a registered port. Unable to activate port openssl. Error: The following dependencies failed to build: openssl Error: Status 1 encountered during processing. So here I just remove the unregistered file: # rm /opt/local/share/man/man3/bn_print.3.gz # port activate openssl @0.9.8j_0 --- Activating openssl @0.9.8j_0 So now it worked. Try py25-hashlib again: # port install py25-hashlib --- Fetching py25-hashlib --- Verifying checksum(s) for py25-hashlib --- Extracting py25-hashlib --- Configuring py25-hashlib --- Building py25-hashlib --- Staging py25-hashlib into destroot --- Installing py25-hashlib @2.5.4_0 --- Activating py25-hashlib @2.5.4_0 --- Cleaning py25-hashlib So now I git t installed. - I got beyond the point where you got stuck. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org
Re: [Haskell-cafe] Ease of Haskell development on OS X?
On 21 Mar 2009, at 01:10, Brandon S. Allbery KF8NH wrote: On 2009 Mar 20, at 17:02, Hans Aberg wrote: Therefore, as mentioned before, it might be best to install the GHC binaries and install libraries like Gtk+ from MacPorts. There is also Intel Gtk+ that binds directly to Aqua, the This won;t work as you expect: since there's a dependency on ghc, the ports version of ghc will be installed. (No, it doesn't behave like BSD ports, and can't: breaking base, which is outside of their control, could have severe consequences, so it doesn't simply accept installed versions of programs.) I'm not sure what you are saying here: installing MacPorts Gtk does not cause its GHC to be installed, nor does it bind to it. The way it works with Gnat, is that there is a GtkAda package which binds to Gtk, and the paths of this package must be set to whatever Gtk one is using. Using an external Gnat binding to MacPorts Gtk works just fine. As for the Intel Gtk package that binds to to Aqua, it is integrated with the Xcode GCC. So one must do some extra tweaking there. Hans Aberg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Ease of Haskell development on OS X?
On 20 Mar 2009, at 21:05, David Leimbach wrote:
Since GHC is written in Haskell, do you need to have another Haskell
compiler installed before GHC 6.10.1 can be installed through
MacPorts?
It bootstraps itself.
??? GHC does or MacPorts does. My experience was that you needed
GHC to build GHC :-)
MacPort developers tweak sources into packages which can install by
themselves. So one just types
sudo port install ghc
and it does the rest. Here is info about ghc:
$ port info ghc
ghc 6.8.3, Revision 1, lang/ghc (Variants: universal, darwin_6,
darwin_7, darwin_8_powerpc, darwin_8_i386, darwin_9_powerpc,
darwin_9_i386, no_opengl)
http://haskell.org/
The Glasgow Haskell Compiler is a robust, fully-featured, optimising
compiler and interactive environment for Haskell 98, GHC compiles
Haskell to either native code or C. It implements numerous
experimental language extensions to Haskell 98, for example:
concurrency, a foreign language interface, multi-parameter type
classes, scoped type variables, existential and universal
quantification, unboxed types, exceptions, weak pointers, and so on.
GHC comes with a generational garbage collector, and a space and
time profiler.
Library Dependencies: readline, gmp
Runtime Dependencies: perl5.8
Platforms: darwin
Maintainers: gwri...@macports.org
However, as someone needs to do the packaging, the versions tend to be
older than from direct sources. So the latter is to be preferred, but
the package manager does the package chasing for you (which is a
problem with Gtk+ installed directly).
Therefore, as mentioned before, it might be best to install the GHC
binaries and install libraries like Gtk+ from MacPorts. There is also
Intel Gtk+ that binds directly to Aqua, the Mac OS X native GUI (for
making native Mac OS X Applications):
http://www.gtk-osx.org/
You need to set of environmental variables UNIX style, but there is a
Mac OS X way, too (see below). In the traditional way, one must be
aware of that the shell 'bash' (see 'man bash') reads different
startup files when called as a login shell (as from the Terminal) and
non-login-shell (as from X11 and xterm). For the former, one can put
the stuff in .profile, and the latter .bashrc. To make things simple,
one can put in .bashrc:
source ~/.profile
thus reading .profile. In .profile, one might put something like the
stuff at the bottom of this letter (which also adds support for the
other package manager, as well admitting user binaries to be installed).
There is another, Mac OS X specific way (also see below): go to
Terminal, and make a directory:
cd
mkdir .MacOSX
cd .MacOSX
touch environment.plist
open -a Xcode environment.plist
The last command opens the file into the Xcode editor, which has a
facility to create the special format for these files. Pne drawback of
this method is the one has to log out and login again to set them.
This assumes you have installed Xcode, wither from the installation
disk, or by signing up as a developer at http://developer.apple.com/
When working with files, it is convenient to set them so that they
open in your favorite program. For that, I have found it convenient to
install a System Preferences panel 'Default Apps' found at
http://www.rubicode.com/Software/
I see now they have one for editing the environment.plist file.
If you come from a non-UNIX (POSIX) platform, then note that in order
to work as root, it is most of the time sufficient to use (from an
administrator account)
sudo -s
The 'root' account is by default disabled (can be started from the
Directory Utility). Also never edit in /usr/ outside /usr/local/, the
other system directories, or /System/ as they belong to the system
installation (Mac OS X user modified system files are out into /
Library/, but often via some other program which does safety checks.)
Hans Aberg
# Add to end of searchpath:
append_path()
{
if ! eval test -z \\${$1##*:$2:*}\ -o -z \\${$1%%*:$2}\ -o -
z \\${$1##$2:*}\ -o -z \\${$1##$2}\ ; then
eval $1=\$$1:$2
fi
}
# Add to beginning of searchpath:
prepend_path()
{
if ! eval test -z \\${$1##*:$2:*}\ -o -z \\${$1%%*:$2}\ -o -
z \\${$1##$2:*}\ -o -z \\${$1##$2}\ ; then
eval $1=$2:\$$1
fi
}
# Set system searchpaths:
# In the case a directory may exist (depending on the program) both
with and without
# parent directory 'share/' (like in the cae of MANPATH and INFOPATH),
the 'share/'
# version is put first, as it is what is used in /usr on Mac OS X
FreeSD UNIX.
# The idea is that if a program is somehow adapted to this platform,
the the stuff will
# be moved to the 'share/' variation, and should thus be ovverride the
unadapted versions.
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/X11R6/bin
MANPATH=/usr/share/man:/usr/X11R6/man
INFOPATH=/usr/share/info
LIBPATH=/usr/lib:/usr/X11R6/lib
# Prepend Fink searchpaths:
test -r /sw/bin/init.sh . /sw/bin/init.sh
Re: [Haskell-cafe] Ease of Haskell development on OS X?
On 20 Mar 2009, at 22:44, Miguel Mitrofanov wrote: Here is info about ghc: $ port info ghc ghc 6.8.3, Revision 1, lang/ghc (Variants: universal, darwin_6, darwin_7, darwin_8_powerpc, darwin_8_i386, darwin_9_powerpc, darwin_9_i386, no_opengl) http://haskell.org/ A bit out of date: MigMit:~ MigMit$ port info ghc ghc @6.10.1, Revision 8 (lang, haskell) ...blah-blah... Maybe, your $(port version) You mean 'port version' (or 'echo $(port version)') :-). is still 1.600? That is right. One should from time-to-time run sudo port -d selfupdate I do not have the ports version of GHC installed. So the version of 'port' itself may affect the info about packages, too, it seems. In addition, one may have to download a new copy from the site. This happened when I made a new system installation (though restore from the Time Machine backup worked fine). Also, updating may break some code - libraries are dynamically linked. I used this for a compile of Scala (in Ada) which links to the MacPorts Gtk+ libraries. And now you tricked me to update - let's see if it breaks. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Ease of Haskell development on OS X?
On 20 Mar 2009, at 22:44, Miguel Mitrofanov wrote: A bit out of date: MigMit:~ MigMit$ port info ghc ghc @6.10.1, Revision 8 (lang, haskell) ...blah-blah... Maybe, your $(port version) is still 1.600? Yes, now it worked: $ port version Version: 1.700 $ port info ghc ghc @6.10.1, Revision 9 (lang, haskell) Variants:darwin_6, darwin_7, darwin_8_i386, darwin_8_powerpc, darwin_9_i386, darwin_9_powerpc ... One more thing to keep in is this line Variants:...: Packages can have variants, and when installing, one can choose between them, and even have several different installed simultaneously, switching between them. This may make a difference on a package like Gtk+. I get: gtk2 @2.14.7, Revision 1 (x11) Variants:darwin_7, darwin_8, no_x11, quartz, universal, x11 ... So when installing it, one should type sudo install gtk2 Also, MacPorts is very careful using full paths to its own components. This makes a very safe build. But it is a problem for libraries if one wants to redistribute them: They are hardcoded to the MacPorts location in /opt/ (calling each other). If one wants to make programs that can be distributed either in /usr/local/ or as Mac OS X native / Applications/, then the only way seems to be to do all the package chasing. Therefore, it might be best trying to use http://www.gtk-osx.org/ But it will then only work on Intel Macs (or at least when I checked it out). Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Theory about uncurried functions
On 5 Mar 2009, at 13:29, Daniel Fischer wrote: In standard NBG set theory, it is easy to prove that card(P(N)) == card(R). No, it is an axiom: Cohen showed in 1963 (mentioned in Mendelson, Introduction to Mathematical Logic) that the continuum hypothesis (CH) is independent of NBG+(AC)+(Axiom of Restriction), where AC is the axiom of choice. Thus you can assume CH or its negation (which is intuitively somewhat strange). AC is independent of NGB, so you can assume it or its negation (also intuitively strange), though GHC (generalized CH, for any cardinality) + NBG implies AC (result by Sierpinski 1947 and Specker 1954). GHC says that for any set x, there are no cardinalities between card x and card 2^x (the power-set cardinality). Since card ω card R by Cantors diagonal method, and card R = card 2^ω since R can be constructed out of binary sequences (and since the interval [0, 1] and R can be shown having the same cardinalities), GHC implies card R = card 2^ω. (Here, ω is a lower case omega, denoting the first infinite ordinal.) Hans Aberg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Theory about uncurried functions
On 5 Mar 2009, at 15:12, Daniel Fischer wrote: No, it is an axiom: Cohen showed in 1963 (mentioned in Mendelson, Introduction to Mathematical Logic) that the continuum hypothesis (CH) is independent of NBG+(AC)+(Axiom of Restriction), where AC is the axiom of choice. Yes, but the continuum hypothesis is 2^Aleph_0 == Aleph_1, which is quite something different from 2^Aleph_0 == card(R). Yes, right, card R = 2^Aleph_0, as you said, and Aleph_1 is defined as the smallest cardinal greater than Aleph_0. Hans Aberg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Theory about uncurried functions
On 5 Mar 2009, at 15:23, Daniel Fischer wrote:
Just to flesh this up a bit:
let f : P(N) - R be given by f(M) = sum [2*3^(-k) | k - M ]
f is easily seen to be injective.
define g : (0,1) - P(N) by
let x = sum [a_k*2^(-k) | k in N (\{0}), a_k in {0,1}, infinitely
many a_k =
1]
and then g(x) = {k | a_k = 1}
again clearly g is an injection.
Now the Cantor-Bernstein theorem asserts there is a bijection
between the two
sets.
I think one just defines an equivalence relation of elements mapped to
each other by a finite number of iterations of f o g and g o f. The
equivalence classes are then at most countable. So one can set up a
bijection on each equivalence class: easy for at most countable sets.
Then paste it together. The axiom of choice probably implicit here.
Hans Aberg
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Re: [Haskell-cafe] Re: Theory about uncurried functions
On 5 Mar 2009, at 17:06, Daniel Fischer wrote: Cantor-Bernstein doesn't require choice (may be different for intuitionists). http://en.wikipedia.org/wiki/Cantor-Bernstein_theorem Yes, that is right, Mendelson says that. - I find it hard to figure out when it is used, as it is so intuitive. Mendelson says AC is in fact equivalent proving all x, y: card x = card y or card y = card x Hans Aberg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Theory about uncurried functions
On 3 Mar 2009, at 10:43, Peter Verswyvelen wrote: Lambda calculus is a nice theory in which every function always has one input and one output. Functions with multiple arguments can be simulated because functions are first class and hence a function can return a function. Multiple outputs cannot be done, one must embed these outputs in some data type, e.g. using a tuple, or one must use continuation passing style. Now, does a similar theory exist of functions that always have one input and one output, but these inputs and outputs are *always* tuples? Or maybe this does not make any sense? I think most of the replies have already described it, but the Church's lambda-calculus is just a minimal theory describing a way to construct functions, which turns out to be quite general, including all algorithms. The first lambda-calculus he describes in his book does not even include the constant functions - for some reason it is convenient. So if you want to have more, just add it. That is why functional computer languages like Haskell can exist. As for currying, it builds on the fact that in the category of sets (but others may not have it) one has a natural equivalence (arguments can also be functions) psi: Hom(A x B, C) -- Hom(A, Hom(B, C)) f |- (a |- (b |- f(a, b))) ((a, b) |- g(a)(b)) -| g So it simply means that set-theoretic products can be rewritten into iterated functions. (Strictly speaking, currying involves a choice of natural equivalence psi.) In axiomatic set theory, it is common to construct tuplets (i.e., set- theoretic products) so that (x) = x, (x_1, ..., x_n) = ((x_1, ..., x_(n-1), x_n), and one might set () to the empty set (so that, for example, the real R ^0 has only one point). The recursive formula has slipped into functional languages. Pure math, unless there are special requirements, uses naive set theory in which that recursion formula would not be used: in computer lingo, it corresponds to the implementation (axiomatic set theory), and is not part of the interface (naive set theory). By contrast, in lists, [x] is not the same as x. (If S is a set, the set of lists with elements from S is the free monoid on S.) But you might view f() as passing the object () to f, f(x) passes x to f, and f(x_1, ..., x_n) passes (x_1, ..., x_n) to f. So the only addition needed is to add the objects (x_1, ..., x_n), n = 0, 1, 2, ..., to your language. You can still curry the functions if you like to - a convention, just as already noted. Hans Aberg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Origins of '$'
On 8 Dec 2008, at 23:15, Joachim Breitner wrote: Am Montag, den 08.12.2008, 15:59 -0600 schrieb Nathan Bloomfield: Slightly off topic, but the A^B notation for hom-sets also makes the natural isomorphism we call currying expressable as A^(BxC) = (A^B) ^C. So A^(B+C) = A^B × A^C ? Oh, right, I guess that’s actually true:... I posted some of those relations for lambda-calculus two days ago (this thread). It is so very off-topic, because one can reverse the process, take those operators and some relations, and show it contains the lambda- calculus (or so I remember, don't recall details). Then one problem is that these operators are not so intuitive for all practical purposes. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Origins of '$'
On 7 Dec 2008, at 11:34, Luke Palmer wrote: On Sun, Dec 7, 2008 at 3:05 AM, Hans Aberg [EMAIL PROTECTED] wrote: One can define operators a ^ b := b(a) -- Application in inverse. (a * b)(x) := b(a(x)) -- Function composition in inverse. (a + b)(x) := a(x) * b(x) O(x) := I -- Constant function returning identity. I(x) := x -- Identity. and use them to define lambda calculus (suffices with the first four; Church reverses the order of *). The simple elegance of writing this encoding just increased my already infinite love of Haskell by another cardinality. a .^ b = b a (a .* b) x = b (a x) (a .+ b) x = a x .* b x o x = i i x = x toNat x = x (+1) 0 fromNat n = foldr (.) id . replicate n I have some more notes on this that you might translate, if possible (see below). If one implements integers this way, time complexity of the operators will be of high order, but it is in fact due to representing n in effect as 1+...+1. If one represents them, using these operators, in a positional notation system, that should be fixed, though there is a lot of other overhead. Hans Associativity: a*(b*c) = (a*b)*c, a+(b+c) = (a+b)+c RHS Relations: a^O = I, a^I = a a^(b * c) = (a^b)^c a^(b + c) = a^b * a^c a*(b + c) = a*b + a*c LHS Relations: I * a = a, O + a = a, O * a = I ^ a c functor (i.e., c(a*b) = c(a)*c(b), c(I) = I) = (a*b)^c = a^c * b^c (a+b)*c = a*c + b*c I^c = I If n in Natural, f: A - A an endo-function, define f^n := I, if n = 0 f * ... * f,if n 1 |-n times-| The natural number functionals, corresponding to Church's number functionals, are then defined by \bar n(f) := f^k If S(x) := x + 1 (regular integer addition), then \bar n(S)(0) = n Also write (following Hancock) log_x b := \lambda x b Then log_x I = O log_x x = I log_x(a * b) = log_x a + log_x b log_x(a ^ b) = (log_x a) * b,x not free in b. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Origins of '$'
On 7 Dec 2008, at 04:30, George Pollard wrote: This is a little bit random, but I was just wondering if anyone knew where the $ low-precedence parenthesis-eliminating application operator originated. The Haskell Report doesn't mention anything, and I can't search for $ on Google. So... who thought it up? Does it originate in an earlier language, or is it uniquely Haskellish? :) As for the operator itself, it appears in Alonzo Church, The Calculi of Lambda-Conversion, where it is written as exponentiation, like x^f, or typographically as f x One can define operators a ^ b := b(a) -- Application in inverse. (a * b)(x) := b(a(x)) -- Function composition in inverse. (a + b)(x) := a(x) * b(x) O(x) := I -- Constant function returning identity. I(x) := x -- Identity. and use them to define lambda calculus (suffices with the first four; Church reverses the order of *). Then on Church's natural number functionals, these are just the expected natural number operations. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] looking for examples of non-full Functional Dependencies
On 18 Apr 2008, at 20:04, Martin Sulzmann wrote: Let's consider our running example class D a b | a - b instance D a b = D [a] [b] which we can write in CHR notation D a b, D a c == b=c(FD) D [a] [b] = D a b (Inst) These rules overlap. I experimented with translations into GNU Prolog (gprolog). Since = is hard to get working in Prolog unless integrated into unification, I tried (using the idea of rewriting unique existence as functions, possible if one assumes the axiom of choice): class(d, A, b(A)). instance(d, l(A), l(B)) :- class(d, A, B). Then: ?- instance(d, l(A), l(B)). B = b(A) ?- instance(d, l(A), C). C = l(b(A)) ?- instance(d, l(A), l(B)), instance(d, l(A), C). B = b(A) C = l(b(A)) Though I am not sure about the intended semantics, it does produce unique solutions. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] looking for examples of non-full Functional Dependencies
On 25 Apr 2008, at 14:20, Tom Schrijvers wrote: Prolog works under the assumption of a closed world. That's contrary to the open world view of regular type classes. So these aren't the intended semantics. By which I gather you mean the interpretation of :- as logical connective = rather than provability |-? My point, though, was to interpret class a b | a - b as a functional dependency b = b(a) rather than as D a b, D a c == b=c Thus trying to eliminate the use of =. Might that be exploited in the type theory context? Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] looking for examples of non-full Functional Dependencies
On 25 Apr 2008, at 15:38, Tom Schrijvers wrote: Prolog works under the assumption of a closed world. That's contrary to the open world view of regular type classes. So these aren't the intended semantics. By which I gather you mean the interpretation of :- as logical connective = rather than provability |-? What I meant was that when Prolog says there are no more solutions, it doesn't know of any more. In realtiy it means there no more solutions under the closed world assumption. That means there could be more solutions if you haven't told Prolog everything. In this context, there may be more class instances (you simply haven't told the system yet). I had no intention to deal with that problem. Just forget what Prolog says, and when it says there are no more solutions think of it as no more solutions determined. (If one interprets :- as provability |-, there needs to be additional axioms for the object theory, and if the theory is consistent, it becomes possible to prove that there are no more solutions.) My point, though, was to interpret class a b | a - b as a functional dependency b = b(a) rather than as D a b, D a c == b=c Thus trying to eliminate the use of =. I don't follow you here. I got ?- instance(d, l(A), l(B)). B = b(A) ?- instance(d, l(A), C). C = l(b(A)) so pattern-wise C and l(B) are the same. But I do not bother introduce an explicit operator =. So at least in this case, if say D [a] Int will be reject as Int is not of the feom l(_). If one has D [Int] [Char] and tries to define D [Int] [Float], the leads to trying to associate the implicit b(Int) with both Char and Float, which would be rejected. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Funny State monad dependency
When I load the State module in Hugs, then I can define the function f below, but I do not immediately see exactly what function return returns. Explanation welcome. For example: f [2..4] [6..9] [6,7,8,9,6,7,8,9,6,7,8,9] That is, it just repeats the second argument as many times as the length of the second argument. Hans Aberg import Control.Monad.State f :: Monad a = a b - a c - a c f x y = x = (return y) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Funny State monad dependency
On 16 Apr 2008, at 15:22, Daniel Fischer wrote: The point is the instance Monad ((-) a) where return x = const x f = g = \x - g (f x) x which is defined in Control.Monad.Instances... Thank you. I suspected there was an instance somewhere, and I wanted to know where it is defined. (try in GHCI: Prelude let f x y = x = (return y) Prelude :t f f :: (Monad ((-) a), Monad m) = m a - m b - m b ). It works in Hugs too. If I don't import Control.Monad.State, then f :: (Monad a, Monad ((-) b)) = a b - a c - a c This is imported into Control.Monad.State and hence the instance is visible. By the type of (=), (return y) must have type (a - m b), on the other hand, if y has type c, then (return y) has type (m' c) for some monad m'. Unifying m' c and a - m b gives then m' === ((-) a) and c === m b. Now according to the instance, return y === const y, so f is the same as g x y = x = (const y). Good to know the details. Thanks. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Funny State monad dependency
On 16 Apr 2008, at 15:14, Miguel Mitrofanov wrote: Before somebody noticed: I'm wrong. It's not List monad, but also a (-) x monad, also defined in Control.Monad. Therefore, return y is just const y. Therefore, x = (return y) = x = (const y) = x y Right. It is an interesting monad, but it may cause unexpected effect, in view of its implicit name. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] instance Monad m = Functor m
On 9 Apr 2008, at 17:49, Henning Thielemann wrote: Additionally I see the problem, that we put more interpretation into standard symbols by convention. Programming is not only about the most general formulation of an algorithm but also about error detection. E.g. you cannot compare complex numbers in a natural way, that is x (y :: Complex Rational) is probably a programming error. However, some people might be happy if () is defined by lexicgraphic ordering. This way complex numbers can be used as keys in a Data.Map. But then accidental uses of () could no longer be detected. (Thus I voted for a different class for keys to be used in Data.Map, Data.Set et.al.) If one just needs to compare equal and unequal elements, then a hash- map is faster than a balanced tree map, and a total order is not needed. So those that want to use complex numbers as keys perhaps have not considered that possibility. And if one considers a total order () for all data types, then if that includes functions, then it may happen that two equal functions f, g satisfy f g. So it would not have the expected semantic properties. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] instance Monad m = Functor m
On 9 Apr 2008, at 11:26, Jules Bean wrote: Using 'hugs -98', I noticed it accepts: instance Monad m = Functor m where fmap f x = x = return.f Has this been considered (say) as a part of the upcoming Haskell Prime? This forbids any Functors which are not monads. Unless you allow overlapping instances... I see it as a Haskell limitation of not being able to indicate the function names in the class definition head: If one could write say class Monoid (a; unit, mult) where unit :: a mult :: a - a - a then it is possible to say instance Monoid ([]; [], (++)) where -- 'unit' already defined -- definition of (++) Similarly: class Functor (m; fmap) where fmap :: (a - b) - (m a - m b) instance Monad m = Functor (m, mmap) where mmap f x = x = return.f - For backwards compatibility, if the function names are not indicated, one gets the declaration names as default. I don't know if it is possible to extend the syntax this way, but it would be closer to math usage. And one would avoid duplicate definitions just to indicate different operator names, like: class AdditiveMonoid a where o :: a (+) :: a - a - a as it could be create using class Monoid (a; o, (+)) ...(which of course would not be h98 any more!). It does not work in 'hugs +98' mode; if I avoid the Prelude names by: class Munctor m where mmap :: (a - b) - (m a - m b) instance Monad m = Munctor m where mmap f x = x = return.f I get ERROR - Syntax error in instance head (constructor expected) Other solutions, such as class Functor m = Monad m are frequently discussed. The point is that Monads have a code lifting property, so the functor is already conatained in the current definition. One might want to have away to override, so even if instance Monad m = Functor (m, mmap) functor specialization can take place if one has a more efficeint definition. For example instance Functor ([], mmap) where mmap = map Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] instance Monad m = Functor m
On 9 Apr 2008, at 15:23, Henning Thielemann wrote: I don't know if it is possible to extend the syntax this way, but it would be closer to math usage. And one would avoid duplicate definitions just to indicate different operator names, like: class AdditiveMonoid a where o :: a (+) :: a - a - a as it could be create using class Monoid (a; o, (+)) I also recognized that problem in the past, but didn't know how to solve it. In Haskell 98, methods are resolved using the types of the operands. How would the compiler find out which implementation of (+) to choose for an expression like x+y using your approach? Different names result in different operator hierarchies. So a class like class Monoid (a; unit, mult) where unit :: a mult :: a - a - a must have an instantiation that specifies the names of the operators. In particular, one will need a class (Monoid (a; 0; (+)), ...) = Num a ... if (+) should be used as Monoid.(+) together with Num.(+). Or give an example you think may cause problems, and I will give it a try. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] instance Monad m = Functor m
On 9 Apr 2008, at 15:23, Henning Thielemann wrote: I also recognized that problem in the past, but didn't know how to solve it. In Haskell 98, methods are resolved using the types of the operands. How would the compiler find out which implementation of (+) to choose for an expression like x+y using your approach? I might describe the idea via mangling. So if one has class Magma (a; unit, mult) where unit :: a mult :: a - a - a then instances Monoid (a; 0; (+)) Monoid (a; 1; (*)) should logically equivalent to Monoid_0_+ (a) 0 :: a (+) :: a - a - a Monoid_1_* (a) 1 :: a (*) :: a - a - a or whatever internal mangling that ensures that the names Monoid_0_+ and Monoid_1_* are different. Would this not work? - They code should be essentially a shortcut for defining new classes. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] instance Monad m = Functor m
On 9 Apr 2008, at 16:26, Henning Thielemann wrote: I think a classical example are number sequences which can be considered as rings in two ways: 1. elementwise multiplication 2. convolution and you have some function which invokes the ring multiplication f :: Ring a = a - a and a concrete sequence x :: Sequence Integer what multiplication (elementwise or convolution) shall be used for computing (f x) ? For that problem to arise, one must have, when defining Sequence class Ring (a; o, e, add, mult) ... class (Ring(a; o, e, add, (*)), Ring(a; o, e, add, (**)) = Sequence a It is a good question, but can be avoided by not admitting such constructs. - I will think a bit more on it. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] instance Monad m = Functor m
On 9 Apr 2008, at 16:26, Henning Thielemann wrote: 1. elementwise multiplication 2. convolution and you have some function which invokes the ring multiplication f :: Ring a = a - a and a concrete sequence x :: Sequence Integer what multiplication (elementwise or convolution) shall be used for computing (f x) ? In math, if there is a theorem about a ring, and one wants to apply it to an object which more than one ring structure, one needs to indicate which ring to use. So if I translate, then one might get something like class Ring (a; o, e, add, mult) ... ... class Ring(a; o, e, add, (*)) = Sequence.mult a Ring(a; o, e, add, (**) = Sequence.conv a where ... Then Sequence.mult and Sequence.conv will be treated as different types whenever there is a clash using Sequence only. - I am not sure how this fits into Haskell syntax though. This might be useful, if it can be worked out. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] instance Monad m = Functor m
On 9 Apr 2008, at 17:49, Henning Thielemann wrote: Additionally I see the problem, that we put more interpretation into standard symbols by convention. Programming is not only about the most general formulation of an algorithm but also about error detection. E.g. you cannot compare complex numbers in a natural way, that is x (y :: Complex Rational) is probably a programming error. However, some people might be happy if () is defined by lexicgraphic ordering. This way complex numbers can be used as keys in a Data.Map. But then accidental uses of () could no longer be detected. (Thus I voted for a different class for keys to be used in Data.Map, Data.Set et.al.) I think there it might be convenient with a total order defined on all types, for that data-map sorting purpose you indicate. But it would then be different from the semantic order that some types have. So the former should have a different name. Also, one might have Ordering(LT, EQ, GT, Unrelated) so t can be used on all relations. Also (2*5 == 7) would surprise people, if (*) is the symbol for a general group operation, and we want to use it for the additive group of integers. This is in fact as it should be; the idea is to admit such things: class Group(a; unit, inverse, mult) ... class (Group(a; 0, (-), (+)), Monoid(a; 1, (*)) = Ring(a; 0, 1, (-), (+), (*)) ... -- (or better variable names). instance Ring(a; 0, 1, (-), (+), (*)) = Integer A group can be written additively or multiplicatively, (+) is often reserved for commutative operations. But there is not way to express that, unless one can write class AbelianGroup(a; unit, inverse, mult) where ... satisfying mult a b = mult b a One would need pattern matching to Haskell in order to make this useful. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] instance Monad m = Functor m
On 9 Apr 2008, at 17:49, Henning Thielemann wrote: Also (2*5 == 7) would surprise people, if (*) is the symbol for a general group operation, and we want to use it for the additive group of integers. One might resolve the Num binding of (+) problem by putting all operators into an implicit superclass: Roughly, let T be the set of of most general types, and for each t in T define a mangling string s(t). Then if the operator op :: t is defined somewhere, it is internally defined as class Operator_s(t)_op t where op :: t Then usages of it get implicit class (Operator_s(t)_op t, ...) = Class where ... and instance Operator_s(t)_op t where ... If I now have another class using (+), it need not be derived from Num, as both usages are derivable from an internal class Operator_(+) The mangling of the type via s(t) might be used to generate C++ style name overloading. It will then depend on how much ambiguity one wants to accept in the context. I do not see exactly how this works with Haskell current syntax; just an input. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] deriving
On 8 Apr 2008, at 00:30, Bulat Ziganshin wrote: At least Hugs complains if one does not indent deriving ..., but I do not know what the standard says. If is required, then it can be changed. deriving is a part of data clause and indentation just allows us to continue clause from prev. line. if not indented, deriving will be parsed as separate clause (and btw such clause, standalone deriving was added to ghc 6.8) So it seems that if one uses the word instance instead of deriving, then the compiler can immediately tell when this word appears whether it is a part if the data clause, or the start of a new instance clause. So it can probably be changed, getting rid of deriving which I think is not used elsewhere. It will break a lot of code, but it is easy to change, and also easy to make a compatibility mode. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] instance Monad m = Functor m
Using 'hugs -98', I noticed it accepts: instance Monad m = Functor m where fmap f x = x = return.f Has this been considered (say) as a part of the upcoming Haskell Prime? Hans Aberg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[4]: [Haskell-cafe] deriving
On 8 Apr 2008, at 10:47, Bulat Ziganshin wrote: deriving which I think is not used elsewhere. It will break a lot of code, but it is easy to change, and also easy to make a compatibility mode. it's also easy to replace all the books, update all code repositories and reteach all the programmers if you ready to pay for it all :D I guess it is only the code breaking part that is any concern of standard. It is really up to the companies to pay for courses retraining programmers for the word change. As for the books, it is a good selling opportunity. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[4]: [Haskell-cafe] deriving
On 8 Apr 2008, at 15:26, PR Stanley wrote: I'm sure you could introduce change gradually without too much pain. So then you only have to get the compilers to gradually understand it :-). I personally think deriving is a descriptive term, now that I understand its role better. There are two processes here: deriving, i.e., inheriting an interface; and instantiating, i.e., producing running code. Haskell denotes derivation by =. And data a deriving (b_1, ..., b_k) is really a short for data a instance b_1 where compiler implementation ... instance b_k where compiler implementation So instance seems the word that should have been used. But discussions of a change seems is likely just a café thing - I must go finishing mine :-). I suppose you could consider specialize or instanciate but both those terms are very closely associated with OO and deriving an instance of a class with a type isn't quite like instantiation or even specialisation. So then you introduce a new keyword and screwing up all existing code. We want a single word which is equivalent to derives from. Deriving by itself can seem a bit ambiguous at first. What about the already used =? Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] deriving
On 8 Apr 2008, at 16:32, Anton van Straaten wrote: There are two processes here: deriving, i.e., inheriting an interface; and instantiating, i.e., producing running code. Haskell denotes derivation by =. And data a deriving (b_1, ..., b_k) is really a short for data a instance b_1 where compiler implementation ... instance b_k where compiler implementation So instance seems the word that should have been used. How about making deriving x an expression which means: instance x where compiler implementation This innovative solution will minimize changes to the Haskell compiler, documentation, and programmer's brains. So what is the difference from the current state? They way you have written it, one can say data A ... deriving Eq A Is that what you want? Seriously, there's only so much connotational meaning you can pack into or extract from a keyword. Ultimately, programming language keywords follow the rule given by Humpty Dumpty: When _I_ use a word, it means just what I choose it to mean -- neither more nor less. That is why computer languages are what they are. Think of C static. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] deriving
On 8 Apr 2008, at 16:57, Anton van Straaten wrote: So what is the difference from the current state? None. See how efficient a solution it is? ;) So for a change, you propose it should be the same. So you are one of those A-programmers :-). Seriously, there's only so much connotational meaning you can pack into or extract from a keyword. Ultimately, programming language keywords follow the rule given by Humpty Dumpty: When _I_ use a word, it means just what I choose it to mean -- neither more nor less. So your favorite language must be Humpty?! :-) Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: deriving
On 8 Apr 2008, at 17:03, Christian Maeder wrote: deriving Eq i.e. following data List a = List a creates an instance like: instance Eq a = Eq (List a) where compiler implementation The problem was discussed for Stand-alone deriving declarations: http://www.haskell.org/ghc/docs/latest/html/users_guide/deriving.html There is a difference between data Foo a = Bar a | Baz String deriving instance Eq a = Eq (Foo a) and data Eq a = Foo a = Bar a | Baz String deriving (Eq) The second is more restrictive, as it requires Eq for the construction of Foo a, whereas the first could be construed to mean that Eq a is only required for the construction of Eq(Foo a). So the first could be used without Eq a if Eq(Foo a) is not needed. This is good when constructing libraries for general types. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Function Precedence
On 2 Apr 2008, at 16:20, Loup Vaillant wrote: class AdditiveSemiMonoid a where (+) :: a - a - a Err, why *semi* monoid? Plain monoid would not be accurate? I found an example where it is crucial that the monoid has a unit: When given a monoid m, then one can also define an m-algebra, by giving a structure map (works in 'hugs -98'): class Monad m = MAlgebra m a where smap :: m a - a Now, the set of lists on a set A is just the free monoid with base A; the list monad identifies the free monoids, i.e., the lists. So this then gives Haskell interpretation class Monoid a where unit :: a (***) :: a - a - a instance Monoid a = MAlgebra [] a where smap [] = unit smap (x:xs) = x *** smap xs Here, I use (***) to not clash with the Prelude (*). But the function product here shows up as the structure map of a multiplicative monoid. Similarly, sum is the structure map of the additive monoids. And (++) is just the monoid multiplication of the free monoids. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] deriving
On 7 Apr 2008, at 21:15, Dan Weston wrote: To answer your second question (which everyone else ignored): Yes. A different keyword might have been more descriptive, such as automatically_deriving_instances_for. They are called instantiations, which Haskell can supply automatically in some cases. And there is already a keyword instance for that - in general, it is good to keep down the number of keywords. So data Bool = False | True instance (Eq, Ord, Enum, Read, Show, Bounded) might have been better. But here, one would have to think about how the compiler should be able to distinguish data Bool = False | True instance (Eq) from data Bool = False | True instance Eq Bool where x == y = ... One wants to be able to do that with as little lookahead as possible. Hans Aberg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] deriving
On 7 Apr 2008, at 21:48, Brandon S. Allbery KF8NH wrote: But here, one would have to think about how the compiler should be able to distinguish data Bool = False | True instance (Eq) from data Bool = False | True instance Eq Bool where x == y = ... Layout already does that, doesn't it? The former, being indented, is a continuation line. At least Hugs complains if one does not indent deriving ..., but I do not know what the standard says. If is required, then it can be changed. Hans ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
