Re: [Haskell-cafe] Haskell development in Mac OS X after Gatekeeper
Well, the command-line tools are now available as a standalone package[1] separate from Xcode[2], so Apple's taken notice of and responded positively to large efforts like Homebrew and MacRuby. With that in mind, I don't think it's unreasonable to think this support also applies to other users of those tools, although the overall impact on source building is unclear so far. I haven't been able to find anything specific to that, yet. But Gatekeeper isn't for programmers and the like. It's for people who don't even know where the menu option is. That's why there's an option to shut it off. What's your setup like that you can't even use gdb in your own directory? That sounds unusual. And you can turn off the warning, either globally or selectively.[3][4] [1]: http://kennethreitz.com/xcode-gcc-and-homebrew.html [2]: https://developer.apple.com/downloads/index.action [3]: http://osxdaily.com/2010/03/29/disable-the-are-you-sure-you-want-to-open-this-file-warning-dialogue-in-mac-os-x/ [4]: http://osxdaily.com/2010/09/12/disable-application-downloaded-from-the-internet-message-in-mac-os-x/ Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes. -- Michael R. Fellows == PublicKey.asc Description: application/apple-msg-attachment On Feb 19, 2012, at 8:27 PM, Richard O'Keefe wrote: On 20/02/2012, at 1:01 PM, Tom Murphy wrote: Does anyone know what this will mean for the future of Haskell development in OS X?: http://www.apple.com/macosx/mountain-lion/security.html Quoting that document: Or you can install all apps from anywhere, just as you can today. You can even temporarily override your setting by Control-clicking, and install any app at any time. Gatekeeper leaves it all up to you. So in the *short* term, it makes little difference. 1) Writing software for widespread use (a security setting is to only run software from the App Store, and I'd like to have my software function on users' computers.) *Short* term, the most that will happen is that people will have to say yeah yeah I know just let me have it OK?. Already in 10.6 there was this nagging feature where you click on a downloaded document and it says this was downloaded, do you really want to open it and it takes a painfully long time bouncing in the dock before that dialogue box comes up. Heck, I have to provide an administrator account password when I want to run GDB in my own directory on my own program. (And you have to love the way they removed the MacOS equivalent of truss because it was superceded by DTrace, but you have to be superuser to use DTrace...) *Short* term, it's just more continuing low-level harassment by Apple (even if perhaps with good intentions). Long term, well, there's a reason why I keep Solaris, Linux, and OpenBSD around... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe signature.asc Description: Message signed with OpenPGP using GPGMail ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell development in Mac OS X after Gatekeeper
As has been mentioned, it's already possible to override Gatekeeper on a per-app basis, and what I've seen so far is that it operates just as the download warning: once you get past the first check, it never bothers you again. Is it unreasonable for your users to open it that way once? As for signing, there's nothing exclusive to Xcode there. Just the `codesign` tool available as usual. Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes. -- Michael R. Fellows == PublicKey.asc Description: application/apple-msg-attachment On Feb 19, 2012, at 9:19 PM, Tom Murphy wrote: On 2/19/12, Austin Seipp mad@gmail.com wrote: On Sun, Feb 19, 2012 at 6:01 PM, Tom Murphy amin...@gmail.com wrote: 0) Distributing non-Cocoa-built apps, even if you're approved by Apple Do you just mean binaries that you expect users run under /usr/local/bin or something, not app bundles? If that's the case, I cannot say if the same restrictions will apply. Actually, what I was more concerned about was the ability to distribute a full Mac application, with a GUI, made with a method other than calling Haskell from Objective-C. It seems that *none* of these applications will be usable by anyone except users with all security settings turned off (it doesn't sound great in a user manual: Every time you run this program, be sure to turn the malware-detector all the way off) The reason I'm concerned is that having a security signature requires a membership to the Apple Developers program, which is exclusively for XCode [0]. Isn't it logical to assume that the signature-bundling process [1] occurs within XCode? (I'm assuming the digital summary of the contents of the application is a hash, which (I think) would imply that XCode-compilation would have to be the final step in the development chain) Which (again, unless I'm reading it wrong) means that most Haskell OS X GUI work (incl. FRP) goes out the window?! amindfv / Tom [0] Not to mention $100 every year! [1] Digital signatures are created by combining a secret key known only to the developer with a digital summary of the contents of the application. It’s all wrapped together in an encrypted file that becomes part of the app. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe signature.asc Description: Message signed with OpenPGP using GPGMail ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell development in Mac OS X after Gatekeeper
In fact, since Gatekeeper, by design, can only quarantine applications acquired through the App Store or a download (or any other method which applies the quarantine flag), it may be entirely irrelevant for you depending on how you distribute. Applications on physical media are exempt, source builds are exempt, as are apps you create. Anything you've already run is similarly trusted, and anything you have to build yourself is, as well. It's fairly developer-friendly, really. Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes. -- Michael R. Fellows == PublicKey.asc Description: application/apple-msg-attachment signature.asc Description: Message signed with OpenPGP using GPGMail ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Off-topic: Mathematics
Statistics questions tend to end up on http://stats.stackexchange.com/, so you could try that, too. It's a well-informed community. Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes…. -- Michael R. Fellows and Ian Parberry == 398E692F.gpg Description: application/apple-msg-attachment On Aug 30, 2011, at 2:04 PM, Andrew Coppin wrote: On 29/08/2011 01:13 PM, Christopher Done wrote: There's also #math on freenode, but it's a scary wilderness. On 29 August 2011 13:34, Benedict Eastaughionf...@gmail.com wrote: On 29 August 2011 09:34, Andrew Coppinandrewcop...@btinternet.com wrote: This is fairly wildly off-topic but... does anybody know of a good forum where I can ask questions about mathematics and get authoritative answers? Apart from math.stackexchange.com and mathoverflow.net, which people have already mentioned, people often discuss mathematics on #haskell-blah on Freenode. I know of several places where I can ask maths questions and half a dozen people will take guesses at what the correct solution might be. I haven't yet found anywhere where I can say when would a chi-squared test be more appropriate than a KS test? and get an informed, knowledgeable answer. (Answers from people who /know/ what they're talking about rather than just /think/ they know.) Anyway, from this thread I've got the names of a few places to start looking. And that's really what I was hoping for. Thanks for the tips. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe signature.asc Description: Message signed with OpenPGP using GPGMail ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Off-topic: Mathematics
The http://math.stackexchange.com/ for normal questions, http://mathoverflow.net/ for research level questions. Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes. -- Edsger Dijkstra == 398E692F.gpg Description: application/apple-msg-attachment On Aug 29, 2011, at 4:34 AM, Andrew Coppin wrote: This is fairly wildly off-topic but... does anybody know of a good forum where I can ask questions about mathematics and get authoritative answers? (Apart from go visit the nearest university, that is.) ___ 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] Truly Really Off-topic: (Was: Mathematics)
Better? Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes…. -- Michael R. Fellows and Ian Parberry == 398E692F.gpg Description: application/apple-msg-attachment On Aug 29, 2011, at 11:47 AM, Gwern Branwen wrote: Michael R. Fellows and Ian Parberry ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Truly Really Off-topic: (Was: Mathematics)
In fairness, I already knew it wasn't an actual Dijkstra quote. It's just one that gets thrown around with his name on it. The origins were misty enough that I just decided to pick the one that pop culture chose. Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes…. -- Michael R. Fellows and Ian Parberry == 398E692F.gpg Description: application/apple-msg-attachment On Aug 29, 2011, at 12:08 PM, Jack Henahan wrote: Better? Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes…. -- Michael R. Fellows and Ian Parberry == 398E692F.gpg On Aug 29, 2011, at 11:47 AM, Gwern Branwen wrote: Michael R. Fellows and Ian Parberry ___ 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] why the name lambda calculus?
It's always been my understanding that calculi were systems that defined particular symbols and the legal methods of their manipulation in the context of a particular calculus. The point, generally (har har), seems to be abstraction. The lambda calculus describes computation without actually implementing it, the predicate/propositional calculi describe logic without necessarily containing any explicit logical statements. Algebras, on the other hand, are structures whose properties are defined by a (usually) small number of properties and axioms. A Boolean algebra is a 6-tuple (A, ∧, ∨, ¬, ⊥, ⊤) such that for all a, b, c in A, associativity, commutativity, absorption, distributivity, and complement axioms all hold. An algebra over a field describes a vector space with a bilinear vector product. The other axioms that must hold depend on the particular vector space, though. Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes. -- Edsger Dijkstra == 398E692F.gpg Description: application/apple-msg-attachment On Aug 24, 2011, at 9:20 AM, Dominic Mulligan wrote: On Wed, 2011-08-24 at 14:01 +0100, Tony Finch wrote: Ezra Cooper e...@ezrakilty.net wrote: I believe this to be a general trait of things described as calculi--that they have some form of name-binders, but I have never seen that observation written down. Combinator calculi are a counter-example. As is the propositional calculus. I seem to remember Joe Wells once asking Wilfrid Hodges what he thought the definition of a calculus was. He didn't provide a convincing definition. ___ 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] why the name lambda calculus?
The short answer is because Church said so. But yes, it is basically because λ is the abstraction operator in the calculus. Why not alpha or beta calculus? What would we call alpha and beta conversion, then? :D On Aug 21, 2011, at 12:37 PM, C K Kashyap wrote: Hi, Can someone please tell me what is the root of the name lambda calculus? Is it just because of the symbol lambda that is used? Why not alpha or beta calculus? Regards, Kashyap ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes. -- Edsger Dijkstra == 398E692F.gpg Description: application/apple-msg-attachment ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Problems building lambdabot on osx
I didn't have any trouble building lambdabot when linking to readline built through Homebrew. Currently using Lion, Xcode 4.1, and GHC 7.0.4. On Aug 9, 2011, at 11:59 AM, Brandon Allbery wrote: On Mon, Aug 8, 2011 at 21:38, Adam Turoff adam.tur...@gmail.com wrote: First, there's the issue with linking against libiconv, which is solved this way: cabal install --extra-lib-dirs=/usr/lib That leaves a whole mess of link errors against libHSreadline: Yes, because now it's finding the system readline, which isn't actually readline (Apple ships a readline which is actually BSD editline, so you get missing symbols for things editline doesn't support such as completion). I think you'll need to temporarily deactivate MacPorts' iconv instead of using --extra-lib-dirs. This can't really be fixed by either GHC or MacPorts; there doesn't seem to be a good solution as yet, although the MacPorts folks may end up implementing a hacky solution because Apple has introduced *another* MacPorts-breaking library conflict in Lion (libnotify). -- 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 Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes. -- Edsger Dijkstra == 398E692F.gpg Description: application/apple-msg-attachment ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] XCode Dependency for HP on Mac
http://developer.apple.com/devcenter/mac/index.action Go there. Log in (free account). Download Xcode 3.2.6. If you want the full complement of blessed UNIX-y tools, you have to get Xcode. Bundling things with the HP is just going to bloat that download and confuse new users more (and my god, the dep-chasing... the number of libs that might have to be piled in on top of it could be absurd). The Dev Tools are standard fare for most everything now. They're my first install on a new system. As much as I would love to be able to just install the UNIX Development tree (really just hardlinks from the Developer folder) and skip all the Xcode Essentials tree, that's just not how it's set up. Apple has to appeal to the masses, and the masses are writing iPhone apps and C in an IDE. 3.2.6 is your best bet now, anyway, since Xcode 4 introduced one or two annoying kinks (though no breakages unless you use 4.2). Also, remind me never to post to the list right after work. I worry I come off as not a very nice person, at all. :/ On Jul 27, 2011, at 3:30 AM, Sean Leather wrote: On Wed, Jul 27, 2011 at 05:55, Tom Murphy wrote: This may sound ignorant because, well, it is ignorant: I know very little about the underlying mechanics here. Installing the Haskell Platform currently requires XCode developer tools. To get XCode on my 10.6 machine, I... ... will check out the related discussion: http://thread.gmane.org/gmane.comp.lang.haskell.cafe/89745 Regards, Sean ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes. -- Edsger Dijkstra == 398E692F.gpg Description: application/apple-msg-attachment PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why aren't files flushed at exit?
Is there really no question? I question the assertion, for one. Just because a language allows a bad habit doesn't mean it's a feature. Leaving your handles open can lead to unpredictable results, which is somewhat anathema to the idea of correct programs, unless broken features are part of your spec. Out of curiosity, which languages `get this right', to your way of thinking? On Jul 17, 2011, at 12:40 PM, Donn Cave wrote: There's no question, if there were two competing Haskell library implementations, GHC and one that worked like buffered I/O in other languages, which one would better support Haskell programmers. It's too bad that doesn't qualify it as valid bug. Donn ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe Jack Henahan jhena...@uvm.edu == Computer science is no more about computers than astronomy is about telescopes. -- Edsger Dijkstra == 398E692F.gpg Description: application/apple-msg-attachment PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: docidx-1.0.0
I've been using docidx for a while now. It's a great little tool. I highly recommend to anyone looking for a centralized documentation tool. Jack On Jul 15, 2011, at 8:38 AM, Andy Gimblett wrote: Hi all. I'd like to announce docidx, a new tool for Haskell documentation: http://hackage.haskell.org/package/docidx http://github.com/gimbo/docidx.hs docidx is a program which creates a static HTML page indexing your installed packages, with links to your local haddock docs and to each package's hackage page. It covers global and user packages, and handles multiple installed versions sensibly. Here's how the output looks: http://github.com/gimbo/docidx.hs/raw/master/examples/example.png The idea is to complement the index by module name which Cabal creates and maintains. Sometimes you want to find things by package. :-) (But note that unlike Cabal's index, docidx's isn't automatically updated when you install a new package; so, I run it once an hour from cron.) Please see the github page for more details, including customisation options. Hopefully somebody will find this useful. Maybe one day it could be part of cabal-install? :-) Thanks! -Andy PS: A bit of history/due credit: Martijn van Steenbergen did something similar in PHP in early 2009: http://thread.gmane.org/gmane.comp.lang.haskell.cafe/53531/focus=53572 ; then I wrote a static version in Python later that year: http://gimbo.org.uk/blog/2009/09/23/ ; then Andy Price ported that to Haskell: https://github.com/andyprice/docidx.hs ; finally, I rewrote that to build the index via Cabal rather than walking the filesystem directly - and here we are. -- Andy Gimblett hask...@gimbo.org.uk ___ 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] Baffling Hackage build log
No problems here (OS X.6). Baffling, indeed. On Jul 12, 2011, at 7:58 PM, wren ng thornton wrote: As a dutiful package maintainer I just checked to make sure unification-fd built correctly on Hackage. Unfortunately it didn't, and it gives this inscrutable error log: cabal: There is no package named unification-fd. Perhaps you need to run 'cabal update' first? Something awry on Hackage? -- Live well, ~wren ___ 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] Inconsistent trailing comma in export list and record syntax
Well, for your example frustration, the leading comma style would sort your
problem nicely. As for the particulars… hmm, not sure. I use leading commas for
both, so I never really noticed.
It may be that since modules simply expose functions to other programs, the
form is syntactically irrelevant except when the module is being loaded.
I am quite curious about it now, though, so I hope there are some more
knowledgeable folks with some input.
On Jul 11, 2011, at 4:49 AM, L Corbijn wrote:
Hello,
I'm wondering why the trailing comma is allowed in export syntax, but not in
record syntax, here an example
module Foo (
export1, -- is allowed
) where
data Type = Type {
record1 :: Foo, -- is not allowed
}
To me this seems quite inconsistent and sometimes quite frustrating, imagine
the case that you want to temporarily remove the last record:
data Type = Type {
record1 :: Foo,
--record2 :: Bar
}
this would fail due to an extra comma that has to be commented out.
You could of course say that I'm using a bad style, but it remains that it
seems to be inconsistent to allow a trailing comma in one place and not in
the other. So is there an reason for this?
Lars Corbijn
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Re: [Haskell-cafe] NLP libraries and tools?
Oof, you're liable to wound my (pure) mathematician's pride with remarks like that, wren. :P Now go intone the Litany of Categories as penance. :D I'll start you off… Set, Rel, Top, Ring, Grp, Cat, Hask… On Jul 7, 2011, at 10:53 PM, wren ng thornton wrote: I can't help but be a (meta)theorist. But then, I'm of the firm opinion that theory must be grounded in actual practice, else it belongs more to the realm of theology than science. -- Live well, ~wren ___ 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] NLP libraries and tools?
Heh, I just hit Reply All and I guess the address came in wrong. Ah, well. I strongly agree with you on the state of linguistics, et al. Having done little bits of work in a few of those fields (or at least work _with_ people in them), your comments are spot on. Though perhaps I wouldn't say that mathematics isn't a science (merely because most fields therein satisfy the scientific method). But my glasses may be just a little rosy. :) All that said, I find your points insightful. And don't even get me started on the sloppy math in the social sciences. :D A major issue in the matter of theory/practice drift seems (to me, at least) to be the subject matter's ability to assimilate into pop culture and pseudo-scientific meandering. String theory and some of Penrose's works spring to mind. Sapir-Whorf, relational databases, and the events (perhaps to be read 'hype') leading up to the AI Winter also come to mind. A little knowledge is a dangerous thing, as they say. Perhaps that's just confirmation bias. I may just think of them as examples because they're pet peeves. :D And, naturally, every field wishes it could be mathematics. (Tongue in cheek… mostly) http://xkcd.com/435/ On Jul 9, 2011, at 7:55 PM, wren ng thornton wrote: (Psst, the nlp list is n...@projects.haskell.org :) On 7/9/11 3:10 AM, Jack Henahan wrote: On Jul 7, 2011, at 10:53 PM, wren ng thornton wrote: I can't help but be a (meta)theorist. But then, I'm of the firm opinion that theory must be grounded in actual practice, else it belongs more to the realm of theology than science. Oof, you're liable to wound my (pure) mathematician's pride with remarks like that, wren. :P How's that now? Pure mathematics is perfectly grounded in the practice of mathematics :) I've no qualms with pure maths. Afterall, mathematics isn't trying to model anything (except itself). The problems I have are when the theory branch of a field loses touch with what the field is trying to do in the first place, and consequently ends up arguing over details which can be neither proven nor disproven. It is this which makes them non-scientific and not particularly helpful for practicing scientists. Linguistics is one of the fields where this has happened, but it's by no means the only one (AI, declarative databases, postmodernism,...) There's nothing wrong with not being science. I'm a big fan of the humanities, mathematics, and philosophy. It's only a problem when non-science is pretending to be science: it derails the scientists and it does a disservice to the non-science itself. Non-science is fine; pseudo-science is the problem. For the same reason, I despise math envy and all the pseudo-math that gets bandied about in social sciences wishing they were economics (or economics wishing it were statistics, or statistics wishing it were mathematics). -- Live well, ~wren ___ 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] How to implement the mean function
Additionally, this SO question[0] is nearly identical, and provides a little more elaboration. [0]:http://stackoverflow.com/questions/2376981/haskell-types-frustrating-a-simple-average-function On Jul 1, 2011, at 2:07 AM, Ruohao Li wrote: For mean xs = sum xs / length xs, I got the following: test.hs:8:10: No instance for (Fractional Int) arising from a use of `/' at test.hs:8:10-27 Possible fix: add an instance declaration for (Fractional Int) In the expression: sum xs / length xs In the definition of `mean': mean xs = sum xs / length xs test.hs:8:10: Couldn't match expected type `b' against inferred type `Int' `b' is a rigid type variable bound by the type signature for `mean' at test.hs:7:27 In the expression: sum xs / length xs In the definition of `mean': mean xs = sum xs / length xs test.hs:8:19: Couldn't match expected type `a' against inferred type `Int' `a' is a rigid type variable bound by the type signature for `mean' at test.hs:7:13 In the second argument of `(/)', namely `length xs' In the expression: sum xs / length xs In the definition of `mean': mean xs = sum xs / length xs On Fri, Jul 1, 2011 at 2:00 PM, aditya siram aditya.si...@gmail.com wrote: What compiler errors are you getting? -deech On Fri, Jul 1, 2011 at 12:55 AM, Ruohao Li liruo...@gmail.com wrote: Hi guys, I just started learning some Haskell. I want to implement a mean function to compute the mean of a list. The signature of the function is: mean :: (Num a, Fractional b) = [a] - b But when I implement this simple function, the compiler keep whining at me on type errors. I know this is wrong: mean xs = sum xs / length xs But how to get it right? Thanks. ___ 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 Computer Science is no more about computers than astronomy is about telescopes. -- Edsger Dijkstra 398E692F.asc Description: application/apple-msg-attachment PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell and Databases
'Courier New, 18pt' considered harmful? On Jul 1, 2011, at 3:08 PM, Christopher Done wrote: On 1 July 2011 20:51, Yves P limestr...@gmail.com wrote: There is something that bothers me with that text, I can't get to grasp what it is... It's bigger than Godzilla? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe Computer Science is no more about computers than astronomy is about telescopes. -- Edsger Dijkstra 398E692F.asc Description: application/apple-msg-attachment PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [Haskell-beginners] Understanding category theory
Derp, forgot to CC the Cafe. Which ones have you read already? It's difficult to make recommendations without knowing what's already off the table. Additionally, don't be put off if it takes a lot of effort to figure anything out. Math textbooks and so on are unlike any other textbook. It's not unusual to spend a day (or several days) trying to digest a single page of material unless you have a strong mathematical background (or even if you do). This is especially true in the more abstract disciplines (and if there's anything more abstract than category theory, I don't think I've yet encountered it). On Jun 29, 2011, at 8:26 PM, Christopher Howard wrote: Would anyone recommend a particular book or tutorial to help me understand category theory? I've tried reading a few tutorials i've googled, but even the beginner ones are very difficult and seem to assume a lot. Sent from my HTC ___ Beginners mailing list beginn...@haskell.org http://www.haskell.org/mailman/listinfo/beginners Computer Science is no more about computers than astronomy is about telescopes. -- Edsger Dijkstra 398E692F.asc Description: application/apple-msg-attachment PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Help
The error in ghci is Couldn't match expected type `Int' with actual type `[a0]' In the expression: [] In an equation for `p': p [] = [] You've defined p as [String] - Int, but then your base case is p [] = []. [] is not an Int. I changed it to 0 and it'll compile, at least, but I'm not sure if that's the effect you're after. http://hpaste.org/48324 Edited code (really just indentation changes and the change from p [] = [] to p [] = 0) On Jun 25, 2011, at 3:19 PM, Stoyan Peev wrote: First I am using WinHugs. that's the code i made so far but it's still not working: http://hpaste.org/48318 Error: ERROR file:.\kursovazadacha.hs:36 - Type error in explicitly typed binding *** Term : p *** Type : [String] - [a] *** Does not match : [String] - Int I'm still breaking down somewhere ... 2011/6/25 Daniel Patterson lists.hask...@dbp.mm.st: what haskell compiler are you using? And what does the include line do? That does not look like a GHC error message (the only compiler I'm familiar with), but it seems like it is saying that you should not have the extra newlines between the function type signature and declaration. - that's only my guess, based on the assumption that the whitespace is being converted to a syntax with explicit semilcolon line terminations. now, looking at the actual code, the type of the parse function is [a] - [a]. This means that you can parse a list of anything into a list of anything, which doesnt make much sense. This should probably be [String] - [String] (you are parsing a list of strings to a list of strings, yes?). Now the base case of parse (the first case) makes sense, but look at the second case. parse is being given a list of elements (which you have used pattern matching to decompose, but the whole argument, (x:xs), is a list of elements). You are then passing that, unchanged, to eval. This means that eval must take the same type. Does it? how would you apply eval to each element in that list, instead of just applying it to the whole list? On Jun 24, 2011, at 4:31 PM, Stoyan Peev wrote: I found the library myself, and i already put the code in that site: http://hpaste.org/48277 That's what i have tried to do for making the task by calling the one string function by another one: include kursovazadacha parse :: [a] - [a] parse [] = [] parse (x:xs) = eval (x:xs) The error from the compiler: ERROR file:.\list.hs:3 - Syntax error in declaration (unexpected `;', possibly due to bad layout) On Fri, Jun 24, 2011 at 11:20 PM, Daniel Patterson lists.hask...@dbp.mm.st wrote: What have you tried to do in order to make it work for the list, and what error results? What is confusing about the error message? More generally, how could you transform an operation on a single string into one that does the same thing to a list of strings? You've probably talked about higher order functions in your class - would any of the common ones (filter, map, foldr) be helpful here? Would any encapsulate what you are trying to do? If you include these kinds of things, I think you'll find this community to be very helpful; without that (showing what your thought process is, why it isn't working, what seems confusing about what the haskell compiler is telling you, etc), you are not going to get help here. People here are very friendly and willing to help people learn; this is not a place to come to get an assignment finished :) Also, could you put the library you are using (I'm assuming that this is provided by your university) and the code on somewhere like hpaste.org, so that the formatting is not messed up by email, and it is syntax highlighted? On Jun 24, 2011, at 3:57 PM, Stoyan Peev wrote: Hello all, I am experiencing some issues to do my course task in university. I have to write a calculator- function in Haskell. The function argument is a list of strings and also form such list, as each string of the argument made definite action: - If the string has the form of an arithmetic _expression_ - calculate this _expression_. The string result becomes part of the list-result. If the _expression_ contains a variable which is not assigned value, the result is displayed undefined. - If the string has the form- Name = value calculated from the last _expression_ is assigned to the variable with the corresponding name in the list, and in the result list is formed a string with type - If there is not a calculated _expression_ to be assigned to form a string no value. - If the string is non-blank, but there is a species different from the above two case, form the string error. - If the string is empty, incl. when it contains only spaces, in the result there is not form a string. Expressions consist of integers without sign variables, operations + (Addition), - (subtraction), * (multiplication) and / (divide) and
Re: [Haskell-cafe] Haskell Weekly News: Issue 187
You could always just subscribe to the HWN feed on Contemplating Code. I just load up my reader when I don't want to read the text dispatches. Try http://contemplatecode.blogspot.com/feeds/posts/default?alt=rss That's the feed URL I use. Then the one on the mailing list is your plaintext fallback. :D On Jun 23, 2011, at 8:48 PM, Conrad Parker wrote: On 24 June 2011 02:24, Rogan Creswick cresw...@gmail.com wrote: On Thu, Jun 23, 2011 at 11:16 AM, Simon Michael si...@joyful.com wrote: On 6/23/11 10:49 AM, Iustin Pop wrote: FYI, a regular link (though longer) seems more appropriate to me. Don't know if other people feel the same though. I prefer the short links, since it is much easier to keep track of what's going on when reading on a small screen (much of my email reading these days is done on my phone.) I'd prefer to just read an HTML version of HWN on my phone. How about simply sending an HTML email with a plaintext fallback? In the plaintext email I'd prefer full URLs to cut/copy on my computer terminal. Conrad. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe 398E692F.asc Description: application/apple-msg-attachment PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell Weekly News: Issue 187
Whoops, forgot to Reply All. My solution for the '[0] with a link far down the page' issue is just to search for '[0]'. Then it brings me to the link, I can open it if I like, and then I just search again for '[0]' and it brings me back to the context. It's imperfect and requires wraparound search, but it works (assuming they don't just have '[0]' scattered all over the place). I agree in principle, though. I just wish I could get my mail client to render Markdown as HTML. That'd make things so much nicer. On Jun 23, 2011, at 5:26 PM, Albert Y. C. Lai wrote: Picky readers we are. I don't mind URL length. And there are ways to have long URLs in-situ without being a big disruption. I hate the borrowed academic practice of saying [0] and giving the URL two hundred lines later. It worked great on paper in hands because I could stick my finger to the paper to remember where to return. It also works great on real HTML documents because browsers have a back button for the same. It completely fails in plain text email because I can't stick a finger and I can't press the back button. Which one is the bigger disruption: an in-situ long URL that makes me skip oh two lines to continue with the main text? or the URL postponed by two hundred lines so I have to first remember it is [1] not [0] this time, then scroll down several pages to hunt for the URL, and then... I forget where to return to? If people want short URLs, I don't mind that either, but I'm picky on how they are shortened. The shortener should offer the option of showing me the original URL and waiting for me to go ahead or abort. As far as I know this means tinyurl.com only. Thank you for bearing with my rant. [0] No URL for this. [1] No URL for this either. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe 398E692F.asc Description: application/apple-msg-attachment PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [Haskell-beginners] boomBangs xs = [ if x 10 then BOOM! else BANG! | x - xs, odd x]
Hi Anthony. What you've got there is a list comprehension. I'll try to break down what it says for you. The basic structure of a list comprehension is function arguments = [ description of the list ] In this function, the argument 'xs' is a Haskell idiom. We use 'xs' to mean a list of x's. 'xs' doesn't *have* to be a list (since you can call anything 'xs'), but conventionally it is. So 'boomBang xs' simply means the function boomBangs takes a list xs as an argument. Now the odd part, the list comprehension itself. The first part describes what will be in the list, and the second part limits it. What this comprehension does is construct a list of all the odd members of the list 'xs' (in this case, they're numbers) and map BOOM! to values under 10, and BANG! to anything above 10. So what is says is if the nth number in my list is less than 10, I want you to make the nth element of the new list BOOM!, otherwise I want you to make it BANG!. Furthermore, I only want you to consider odd values of x from my list. So testList xs = [ x | x - xs, odd x ] called with the list [1,4,8,9,12,15] would return [1,9,15] -- That is, all the odd members of the list xs Now, if 'x' is the expression 'if x 10 then BOOM! else BANG!', the list returned is instead [BOOM!,BOOM!,BANG!] Decent explanation? Or have I just muddled the issue? On Jun 21, 2011, at 3:58 PM, anthony niro wrote: Hello, My name is Anthony i have few question about Haskell. I was reading a tutorial everything goes well. but now i have few things that i dont understang. HERE: boomBangs xs = [ if x 10 then BOOM! else BANG! | x - xs, odd x] I dont understand this line except the if then else. What is xs? what is the | ? and why doing this| x - xs, odd x] why x - xs? what is that and what is odd x? thx everyone for answer me. ___ Beginners mailing list beginn...@haskell.org http://www.haskell.org/mailman/listinfo/beginners 398E692F.asc Description: application/apple-msg-attachment PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Getting library documentation for installed packages on Windows
John, Run `ghci`, then :m System.Directory getAppUserDataDirectory cabal That'll show you the directory where your cabal config is. On Jun 21, 2011, at 9:03 PM, John Ky wrote: Hi Svein, Where can I find this file on Windows 7 or Windows generally if its all the same? Cheers, -John On 22 June 2011 10:15, Svein Ove Aas sve...@gmail.com wrote: Yes, cabal does this if you have haddock installed. You'll probably have to edit .cabal/config, though. The relevant options should be fairly obvious in there. On Jun 22, 2011 12:52 AM, John Ky newho...@gmail.com wrote: Hi all, Lately I've been finding the Network module missing from the docs I download from the GHC website, which brings me to the question: Is there any way I could generate libraries for this, the core libraries and all installed cabal packages into one reference so I can work offline? Cheers, -John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe 398E692F.asc Description: application/apple-msg-attachment PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell *interpreter* on iPad? (Scheme and Ocaml are there)
Well, strictly speaking, GHC only supports self-cross-compilation, id est porting[1], cf. [2]. For more information on cross compilation generally, refer to the wiki page[3]. Does that answer your question, or did you have something else in mind? [1]:http://hackage.haskell.org/trac/ghc/wiki/Building/Porting [2]:http://hackage.haskell.org/trac/ghc/wiki/CrossCompilation [3]:http://en.wikipedia.org/wiki/Cross_compiler On Jun 19, 2011, at 11:44 AM, Tom Murphy wrote: On 6/18/11, Alexander Solla alex.so...@gmail.com wrote: Since the iPhone OS is pretty much OS X for ARM, and GHC apparently now supports cross-compilation, you can compile GHC for iOS. Can you provide a link for info? I don't understand how this would be done. Thanks Tom ___ 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] Haskell *interpreter* on iPad? (Scheme and Ocaml are there)
I suppose you could make a GUI, by why? Given that you'll have to be working on a jailbroken device, anyway, one could just as well use one of the numerous terminal emulators now floating around for jailbroken iOS. That said, the idea of people writing Haskell on phones and iPads and so on makes me just a little bit grinny. On Jun 18, 2011, at 2:17 PM, Alexander Solla wrote: On Sat, Jun 18, 2011 at 10:46 AM, John Velman vel...@cox.net wrote: To further emphasize, I'd like to type in (or paste in) Haskell code and have it executed on the iPad. To reiterate: Something like Hugs, or ghci on the iPad. Since the iPhone OS is pretty much OS X for ARM, and GHC apparently now supports cross-compilation, you can compile GHC for iOS. I guess you could cross compile Hugs with GCC. Doing so probably isn't trivial, but it should be straightforward. I bet you could even use Xcode to make a graphical user interface to GHCi. ___ 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] Haskell *interpreter* on iPad? (Scheme and Ocaml are there)
Oh, wow, I'd never seen gambitREPL, just the (pretty terrible) iScheme. That's pretty neat. It's probably quite doable, then, but the dev would either be forced into Hugs, or they'd have to implement a more portable GHC. Does such a thing exist already? On Jun 18, 2011, at 3:03 PM, John Velman wrote: On Sat, Jun 18, 2011 at 10:44:01PM +0400, MigMit wrote: Well, this is my point. THERE ARE 3 SCHEME INTERPRETERS in the iPad app store. They run on factory iPads, not jailbroken. The GUI for the gambitREPL (Read, Evaluate, Print, Loop) is just like a console. Input a scheme expression. CR. Answer appears, new prompt. In haskell we need to allow for some way to input layout. I don't recall how Hugs handles this, if at all. There are probably 5 or 10 people out there who want to learn functional programming, and they are studying Scheme on their iPads. Or Ocaml. I don't forsee doing production programming ON THE IPAD, but experimenting, testing some functions, and, by the way, learning Haskell. While I'm fantasizing, something like Hugs or ghci with SOE would really be neat. Sorry for shouting :-) John Velman Well, Haskell is fun, isn't it? And that's what iPhone is perfect for: fun. Back when I had iPod Touch 1G (jailbroken, of course), I used to run Hugs on it. Now I would love to see a Haskell interpreter in the App Store — which, by the way, is possible; as there are Scheme interpreters there, why not Haskell? Отправлено с iPhone Jun 18, 2011, в 22:27, Jack Henahan jhena...@uvm.edu написал(а): I suppose you could make a GUI, by why? Given that you'll have to be working on a jailbroken device, anyway, one could just as well use one of the numerous terminal emulators now floating around for jailbroken iOS. That said, the idea of people writing Haskell on phones and iPads and so on makes me just a little bit grinny. On Jun 18, 2011, at 2:17 PM, Alexander Solla wrote: On Sat, Jun 18, 2011 at 10:46 AM, John Velman vel...@cox.net wrote: To further emphasize, I'd like to type in (or paste in) Haskell code and have it executed on the iPad. To reiterate: Something like Hugs, or ghci on the iPad. Since the iPhone OS is pretty much OS X for ARM, and GHC apparently now supports cross-compilation, you can compile GHC for iOS. I guess you could cross compile Hugs with GCC. Doing so probably isn't trivial, but it should be straightforward. I bet you could even use Xcode to make a graphical user interface to GHCi. ___ 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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
