Re: [Haskell-cafe] indentation with let and do
On Thu, Oct 3, 2013 at 2:31 PM, Corentin Dupont corentin.dup...@gmail.comwrote: test :: Bool - IO () test foo = do let bar = case foo of True - Foo; False - Bar return () while this one does (just adding one space in front of True and False): test :: Bool - IO () test foo = do let bar = case foo of True - Foo; False - Bar return () Do you understand how layout works? Informally, something that is more indented is a continuation of the previous expression, while something equally or less indented is a new expression. In this case, the previous expression is `bar = case foo of` and indenting `True` to the same level as `bar` means you have ended the expression starting with `bar =`. Adding just one extra space indicates that it's still part of `bar =`. (ghc is actually being somewhat lenient here; strictly speaking, you are not indented beyond the `case` so it should have ended the `case` expression. ghc allows some sloppiness like this when there absolutely must be something else after, but there are limits mostly imposed by layout introducers like `let` and `do`.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mystery of an Eq instance
On Sat, Sep 21, 2013 at 12:35 PM, Bardur Arantsson s...@scientician.netwrote: On 2013-09-20 18:31, Brandon Allbery wrote: [--snip--] unless you have a very clever representation that can store in terms of some operation like sin(x) or ln(x).) I may just be hallucinating, but I think this is called describable numbers, i.e. numbers which can described by some (finite) formula. Not sure how useful they would be in practice, though :). I was actually reaching toward a more symbolic representation, like what Mathematica uses. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mystery of an Eq instance
On Sat, Sep 21, 2013 at 12:43 PM, David Thomas davidleotho...@gmail.comwrote: Sure. An interesting, if not terribly relevant, fact is that there are more irrational numbers that we *can't* represent the above way than that we can (IIRC). I think that kinda follows from diagonalization... it does handle more cases than only using rationals, but pretty much by the Cantor diagonal argument there's an infinite (indeed uncountably) number of reals that cannot be captured by any such trick. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Strange exit status behavior from the process package
On Sat, Sep 21, 2013 at 11:12 PM, Michael Xavier mich...@michaelxavier.netwrote: I've run into some strangeness with the process package. When you kill some processes on the command line you correctly get a non-zero exit status. However when using the process package's terminateProcess (which sends a SIGTERM), it returns an ExitSuccess: The 143 you get from the shell is synthetic (and nonportable). Signals are not normal exit codes; WEXITSTATUS is not defined in this case (but often will be 0, as seems to be shown here), instead WTERMSIG will be set to the signal that terminated the process. The caller should be using WIFEXITED / WIFSIGNALED / WIFSTOPPED to determine the cause of the termination and then the appropriate WEXITSTATUS / WTERMSIG / WSTOPSIG call to determine the value. It sounds like the createProcess API does not recognize signal exit at all, and uses WEXITSTATUS even when it is not valid. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mystery of an Eq instance
On Fri, Sep 20, 2013 at 12:17 PM, damodar kulkarni kdamodar2...@gmail.comwrote: Ok, let's say it is the effect of truncation. But then how do you explain this? Prelude sqrt 10.0 == 3.1622776601683795 True Prelude sqrt 10.0 == 3.1622776601683796 True Because there's no reliable difference there. The truncation is in bits (machine's binary representation) NOT decimal digits. A difference of 1 in the final digit is probably within a bit that gets truncated. I suggest you study IEEE floating point a bit. Also, study why computers do not generally store anything like full precision for real numbers. (Hint: you *cannot* store random real numbers in finite space. Only rationals are guaranteed to be storable in their full precision; irrationals require infinite space, unless you have a very clever representation that can store in terms of some operation like sin(x) or ln(x).) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Trouble installing haskeline: ExitFailure 139
On Sat, Sep 14, 2013 at 4:57 PM, David Banas capn.fre...@gmail.com wrote: Has anyone else hit an unexplained *ExitFailure 139* when trying to install the *haskeline* package? 139 sounds like how the shell passes on Segmentation fault (core dumped). -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Proposal: New syntax for Haskell
On Thu, Sep 12, 2013 at 6:00 PM, David Thomas davidleotho...@gmail.comwrote: I've long been interested in a scripting language designed to be spoken. Not interested enough to go about making it happen... but the idea is fascinating and possibly useful. http://en.wikipedia.org/wiki/Shakespeare_(programming_language) ? :) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unary functions and infix notation
On Fri, Sep 6, 2013 at 11:04 AM, Johannes Emerich johan...@emerich.dewrote: Desugaring of an equivalent source file shows that id is applied to the anonymous function, which is then applied to 1. The following example of a function that is not polymorphic in its return type behaves closer to what I would have expected: It does not work. Prelude let z = (\y - True) :: a - Bool Prelude :t (`z` True) interactive:1:2: The operator `z' takes two arguments, but its type `a0 - Bool' has only one In the expression: (`z` True) What is the purpose/reason for this behaviour? Coming from another language, where functions aren't first class, you will probably be used to the notion that a function type is somehow different from any other type. You'll need to unlearn that for functional languages: function types are just as real as (Integer) is, and if I have a type variable somewhere which doesn't have constraints otherwise preventing it, that type variable can end up being (Integer) or (a - a) or (Num c = c - c - c) or (Maybe [x]) or (Maybe (a - a)) or any other (rank-1, i.e. no internal foralls) type. (id) has the type (a - a); in the use mentioned in the first quoted paragraph, this has unified (a) with (b - b) to produce (id :: (b - b) - (b - b)) in order for the whole expression to be typeable. In your second example, you don't have polymorphism where it's needed so it can't infer a type that will work. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to read a file and return a String?
On Wed, Sep 4, 2013 at 10:21 AM, yi lu zhiwudazhanjiang...@gmail.comwrote: I want to read a text file, and store it in a *String*. But readFile will get *IO String*. I search with google and they tell me it is not necessarily to do so. Can you explain to me why is this? Furthermore, How to read a file and store it in a String? You do not do so directly. An IO action is a promise to produce a value, not an actual value. (readFile contains a String in the same way the ls or dir command contains a list of files.) I suggest you take a look at http://learnyouahaskell.com/input-and-output#files-and-streams to see how IO works in Haskell. tl;dr: use do notation (which lets you pretend to a limited extent that you can see the String in an IO String) or = or fmap to attach a callback to the IO promise. readFile = (something that operates on a String and produces an IO whatever) do s - readFile (something that operates on a String and produces an IO whatever) Note that in the end it's still in IO. You can't escape it. (There are actually ways to escape but they will get you into trouble fairly quickly because they don't work the way you want them to.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unexpected behaviour with send and send-buffer setting
On Tue, Sep 3, 2013 at 6:56 PM, Simon Yarde simonya...@me.com wrote: I've found that setting the send buffer size causes send to truncate the ByteString to the buffer size, but that successive sends continue to succeed when the buffer should be full. I see no actual flow control here. That the receiver is blocked does not mean the receiver's *kernel* has not received the packets and buffered them. Also note that send is not synchronous; it cannot know that the receiver has hit its buffer limit --- and the kernel may well have already sent the previous packet, so the send buffer is in fact empty at that point, with the pending packet either in flight or in the receiving kernel's (interrupt time or normal; they are usually distinct. Or, with a sufficiently fancy network card, its own) network buffers. In short, you have not thought through all the possible ramifications, nor considered that the kernel handles packets and buffering independently of your program, nor considered the effects of the non-instantaneous network between sender and receiver. It may or not behave differently when sender and receiver are on the same machine. Do not assume that the kernel will short-circuit here and leave out all the intermediate buffering! The only part you're guaranteed to avoid is the interface with the network hardware. The crux of my line of enquiry is this; how can my application know when to pause in generating its chunked output if send doesn't block and the current non-blocking send behaviour apparently succeeds when the send buffer should be full? I would suggest reading a book on TCP/IP networking. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] World's First Commercial Haskell IDE and Deployment Platform, FP Haskell Center Launches Today
On Tue, Sep 3, 2013 at 3:35 PM, Mathijs Kwik math...@bluescreen303.nlwrote: You can always try the attached docx! :) Which likewise showed nothing. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unexpected behaviour with send and send-buffer setting
On Tue, Sep 3, 2013 at 7:58 PM, Joey Adams joeyadams3.14...@gmail.comwrote: On Tue, Sep 3, 2013 at 6:56 PM, Simon Yarde simonya...@me.com wrote: I'm new to Haskell and have reached an impasse in understanding the behaviour of sockets. The crux of my line of enquiry is this; how can my application know when to pause in generating its chunked output if send doesn't block and the current non-blocking send behaviour apparently succeeds when the send buffer should be full? 'send' will eventually block after enough 'send's without matching 'recv's. As Brandon explains, there is more buffering going on than the send buffer. In particular, the receiving host will accept segments until its buffer fills up. TCP implements flow control (i.e. keeps the sender from flooding the receiver) by Also note that, if you're using TCP, Nagle's algorithm will be turned on unless you specifically turn it off; this is explicitly designed to avoid sending very short packets, by buffering them into larger packets in the kernel network stack up until some timeout or a minimum threshold size is reached. (Protocols such as ssh and telnet turn it off for interactivity.) And if you're using UDP, there's no flow control at all; while packets won't be aggregated á la Nagle, the network stacks on the sending and receiving ends can do pretty much whatever they want with the individual packets. And in either case the socket buffer size is only the last mile: there is no way to control what happens elsewhere, and in particular the interrupt-time received packet handling usually won't know even what socket is the target, much less what buffer size that socket has set. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Template Haskell: let statement in a splice put in the main = do part of a program?
On Sat, Aug 24, 2013 at 11:00 AM, TP paratribulati...@free.fr wrote:
main = do
$(makeLetStatement a)
-- print a
Is that the actual indentation you used? Because it's wrong if so, and the
error you would get is the one you're reporting. Indentation matters in
Haskell.
In an equation for `main': main = do { $(makeLetStatement a) }
You cannot *end* a do with a let-statement; it requires something else
following it. You have nothing following it, as shown by the above fragment
from the error message.
--
brandon s allbery kf8nh sine nomine associates
allber...@gmail.com ballb...@sinenomine.net
unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] abs minBound (0 :: Int) negate minBound == (minBound :: Int)
On Mon, Aug 19, 2013 at 11:43 AM, Kyle Miller kmill31...@gmail.com wrote: Or, three other options: 1) make MIN_INT outside the domain of abs, 2) make the range of abs be some unsigned int type, or 3) use Integer (i.e., use a type which actually represents integers rather than a type which can only handle small integers). I think I would just document that Int is intended to represent a machine word and therefore inherits the behavior of machine words, behavior at its extrema is subject to the CPU behavior as a result, and if consistent behavior is required then Integer should be used. (Indeed, it should probably note that Int is a performance hack; but then you run into all the Data.List etc. functions that use it.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Errors in non-monadic code
On Mon, Aug 19, 2013 at 1:48 PM, jabolo...@google.com wrote: What is the proper way to implement a non-monadic function that checks whether a given value is correct and gives a proper error message otherwise ? What is the recommended option ? * Either String a Preferred, usually, since Nothing is regarded as an error condition of sorts: the Monad instance for Maybe associates Nothing with `fail`, which is invoked on failed pattern matches; likewise it's mzero for MonadPlus and mempty for Monoid, both of which use it (differently) to reflect certain failure scenarios). If nothing else, it would be highly confusing to see Nothing associated with success given its widespread association with failure. Alternatively, have you considered using your own ADT? `data Validity = Success | Failure String` would give you more readable / comprehensible code without needing to worry about assumptions or common usage. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Errors in non-monadic code
On Mon, Aug 19, 2013 at 2:09 PM, Brandon Allbery allber...@gmail.comwrote: Alternatively, have you considered using your own ADT? `data Validity = Success | Failure String` would give you more readable / comprehensible code without needing to worry about assumptions or common usage. Or possibly Valid and Invalid as the constructors This also means you can easily extend it later to include multiple errors, or position information, or other annotations. You could also use it with Monoid and/or the Writer monad to track success/failure in the most appropriate way for your project, instead of being constrained to the behavior of an existing instance. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Errors in non-monadic code
On Mon, Aug 19, 2013 at 2:59 PM, jabolo...@google.com wrote: I'd say that if you were in the context of the IO monad, maybe you'd prefer to use exceptions instead of 'Either' or 'Maybe'. Even in IO, exceptions should be reserved for truly exceptional conditions (of the program cannot safely continue variety), not merely for error checking when this can be described as a normal flow of evaluation. Exceptions are not simply alternative flow of control, even in procedural languages; they are *disruptions* of flow of control. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Database.postgreSQL.Simple - ambigious type
On Sat, Aug 17, 2013 at 1:35 PM, Hartmut Pfarr hartmut0...@googlemail.comwrote: (The example is identical to the first 5-liner-example in the package documentation) As I read it, the example has a typo: it should be using `query_` instead of `query`. See http://hackage.haskell.org/packages/archive/postgresql-simple/0.3.5.0/doc/html/Database-PostgreSQL-Simple.html#g:9for detals. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Database.postgreSQL.Simple - ambigious type
On Sat, Aug 17, 2013 at 5:59 PM, Hartmut Pfarr hartmut0...@googlemail.comwrote: query_ conn select 2 + 2 I've no errors any more. But: I don't see any result (for sure, it is not coeded yet) Yes, because you're not capturing it; it's the return value from `query_`, which you are throwing away above instead of capturing with some kind of `res - query_ ...`. Again, see that section of the documentation I pointed to for how to get results. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Applicative is like an Arrow
On Fri, Aug 16, 2013 at 10:04 AM, Thiago Negri evoh...@gmail.com wrote: I just stumbled upon the Applicative term. Arrows are quite difficult for me to understand at the moment. I guess it needs time to digest. But, as I understand so far, Applicative and Arrows looks like the same thing. Practically, that's not too far off. Arrows, at least as implemented currently, have a number of significant restrictions based on the need for the `arr` combinator to accomplish much of anything; Applicative has, as a result, largely taken over the spot in the Haskell ecosystem that Arrow was originally intended to fill. My understanding is that there's a rework of Arrow in progress that may change this in the future, since *theoretical* Arrows are more distinct, flexible and useful than the current implementation. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Applicative is like an Arrow
On Fri, Aug 16, 2013 at 10:49 AM, Tom Ellis tom-lists-haskell-cafe-2...@jaguarpaw.co.uk wrote: On Fri, Aug 16, 2013 at 10:26:42AM -0400, Brandon Allbery wrote: My understanding is that there's a rework of Arrow in progress that may change this in the future, since *theoretical* Arrows are more distinct, flexible and useful than the current implementation. I'd like to know more about that if you can provide any references. I am using arrows very heavily. It's been mentioned (but not much more) in #haskell IRC, so I don't know details. I also expect it's not going to simply replace the current one, at least not initially; and I think it's supposed to maintain compatibility with the current Arrow because that's just a specialization to the function arrow. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] more gtk help
On Tue, Aug 13, 2013 at 10:45 PM, bri...@aracnet.com wrote: fooBar = do putStrLn foo return True so then I thought, aha!, all I need to do is understand the type of return True and all will be revealed to me. Well, it's this: Control.Monad.Trans.Reader.ReaderT (GHC.Ptr.Ptr Gtk.EExpose) IO Bool just like the error message says. Still don't know what that's supposed to be. I'm having trouble tracking down Control.Monad.Trans.Reader.ReaderT In this case, all you need to know is the Control.Monad.Trans part and the IO underneath; this tells you that you can use `lift` and possibly `liftIO` to get at the IO. fooBar = do liftIO $ putStrLn foo return True If `liftIO` complains about a missing MonadIO instance, file a bug :) but you can also get there by using `lift` to reach it; in this case you only need it once, but for more deeply nested transformers you may need it multiple times (e.g. `lift . lift . lift $ putStrLn foo` for a stack of 3 transformers over IO). -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] llvm on macos
On Sat, Aug 10, 2013 at 7:39 AM, Dominic Steinitz domi...@steinitz.orgwrote: no location info: Warning: Couldn't figure out LLVM version! Make sure you have installed LLVM ghc: could not execute: opt The ghc documentation ( http://www.haskell.org/ghc/docs/7.6.1/html/users_guide/code-generators.html ) says that llvm and clang are installed by default for 10.6 and later. I am on 10.8.3. Apple *still* doesn't ship a full LLVM for some reason. I installed one via MacPorts; Homebrew also has it. Maybe if enough people file bugs with Apple, they'll start providing the whole thing instead of just the parts they use in Xcode. :/ -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Renumbered mailing list posts
On Sat, Aug 10, 2013 at 11:38 AM, Niklas Hambüchen m...@nh2.me wrote: (Also fact that hpaste just went away, invalidating all my links to hpastes, is similarly bad.) Those at least are recoverable, just replace hpaste.org with lpaste.net(content is still there). But still. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] llvm on macos
On Sat, Aug 10, 2013 at 12:53 PM, Dominic Steinitz domi...@steinitz.orgwrote: Thank you very much. I used Homebrew. Now I can compile albeit with a warning. I have yet to try running it. Loading package repa-3.2.3.1 ... linking ... done. You are using a new version of LLVM that hasn't been tested yet! We will try though... There may be some support for requesting specific versions from Homebrew. With MacPorts I can install any or all of LLVM 2.9 through 3.4 (prerelease) and then use port select to specify which one is default (or even make Apple's the default while keeping the MP ones available). -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Installing wxHaskel on Snow Leopard
On Thu, Aug 8, 2013 at 9:54 AM, Eduardo Sato eduardo.s...@gmail.com wrote: The only problem now is that I want to distribute a wxHaskell application on mac OS X. I tried using macosx-app and cabal-macosx ( https://github.com/michaelt/cabal-macosx) to make an app file. It runs fine on my machine, but it fails to run on another computer. I get the following error: Dyld Error Message: Library not loaded: /Users/eduardo/.cabal/lib/wxc-0.90.1.0/ghc-7.6.3/libwxc.dylib. What would be the best way to redistribute wxHaskell apps? This sounds like cabal-macosx was not updated to handle dynamic GHC libraries. (GHC used to default to static; OS X was one of the first platforms to switch to default dynamic.) I know in theory how to deal with this (copy the necessary libraries into the app bundle and use install_name_tool to adjust the references to be bundle-relative) but could not give you exact details. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Installing wxHaskel on Snow Leopard
On Thu, Aug 8, 2013 at 12:04 PM, Eduardo Sato eduardo.s...@gmail.comwrote: Would it be necessary to change Info.plist? I don't believe so; Info.plist is the externally visible interface details, but these libraries should be hidden inside the app bundle and not visible outside of it. When the runtime dynamic library loader is invoked in the context of a bundle, it uses a special token to find bundle-relative internal libraries (see @executable_path and friends in `man 1 dyld`). This is independent of Info.plist, except insofar as existence (not contents) of that plist is part of Apple's definition of bundle. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Alternative name for return
On Tue, Aug 6, 2013 at 4:03 AM, J. Stutterheim j.stutterh...@me.com wrote: I have to admit that I am a bit torn about using `pure`. On the one hand, if you actually have a pure value, it feels pretty intuitive to me. But what about pure (putStrLn Hi) `putStrLn Hi` is not a pure value... Or is there another way to interpret the word pure in this context? I actually have the opposite problem: what's impure about lifting 5 into Maybe or []? `pure` feels IO-targeted. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Alternative name for return
On Tue, Aug 6, 2013 at 9:10 PM, Richard A. O'Keefe o...@cs.otago.ac.nzwrote: I bet you can find an abundance of C programmers who think that strcmp is an intuitive name for string comparison (rather than compression, say). Them and a small and slowly shrinking group of folks who find it intuitive because obviously only the first 6 characters of an imported function are significant :) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why GHC is written in Happy and not a monadic parser library?
On Fri, Aug 2, 2013 at 8:49 PM, blackbox.dev.ml blackbox.dev...@gmail.comwrote: Is there any specific reason why GHC is written in a parser GENERATOR (Happy) and not in MONADIC PARSER COMBINATOR (like parsec)? Is Happy faster / handles better errors / hase some great features or anything else? Most probably because GHC predates practical parser combinators. Happy is just a yacc clone, really; ancient tech. And I would suspect that replacing the parser at this point could get pretty painful. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Sneaky method for var-arg fns?
On Fri, Jul 26, 2013 at 5:08 PM, Micah Cowan mi...@cowan.name wrote: I was wondering if there was a way to do it in pure Haskell (i.e., no GHC pragmas required), and also the specific reason for why the above example doesn't work without the pragma (I think it's just that in general a - b is not syntactically allowed for type specifiers within instance declarations)? The error message you get without the pragma tells you exactly what's wrong, and that's not it. Standard Haskell is *very* conservative about what it allows in an instance declaration; you may not have literal types, nor may you repeat a type variable, only things of the form (Type var1 var2 ...) are permitted. (The (String - String) is not syntactically a problem; it's read as ((-) String String) which would conform *if* it didn't use literal types. You can verify this by rephrasing it in prefix form --- note the error message uses the infix form even if you phrase it as a prefix!) This is widely seen as unnecessarily restrictive. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ordNub
On Sun, Jul 14, 2013 at 7:54 AM, Clark Gaebel cgae...@uwaterloo.ca wrote: Oops sorry I guess my point wasn't clear. Why ord based when hashable is faster? Then there's no reason this has to be in base, it can just be a Did the point about stable fly overhead? -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ordNub
On Mon, Jul 15, 2013 at 10:31 PM, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote: If I understand correctly, this function is proposed to be added to Data.List which lives in base... but the proposals here are about using either Sets from containers or HashSet from unordered-containers; I thought base wasn't supposed to depend on any other package :/ As I understand it, currently we have a double proposal: simple ordNub in Data.List without external dependencies, and the other one in containers and/or unordered-containers as appropriate. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] getting haddock to cooperate with cpp
On Fri, Jul 12, 2013 at 2:25 PM, Evan Laforge qdun...@gmail.com wrote: In the broader scheme, it seems perverse to be using CPP in the first place. I use it to configure imports and exports, e.g. to swap out a driver backend on different OSes, and to export more symbols when testing. Would it make sense to have a haskell version of CPP that provides only these features (e.g. just #ifdef, #else, #endif, and #define) and leaves out the problematic C comments and backslash expectations? You mean http://hackage.haskell.org/package/cpphs ? (although I think it may still do some of that stuff, it does far less than ANSI demands) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Comparing functions
On Thu, Jul 11, 2013 at 1:33 PM, Vlatko Basic vlatko.ba...@gmail.comwrote: data CmpFunction a = CF (a - a - Bool) that contains comparing functions, like ==, , ..., and I'm trying to declare the Show instance for it like this instance Show (CmpFunction a) where show (CF (==)) = ==-- no good show f = case f of-- no good also CBF (==) - == _ - Other but compiler complains for both with This binding for `==' shadows the existing binding imported from `Prelude' at src/Main.hs:6:8-11 (and originally defined in `ghc-prim:GHC.Classes') The problem here isn't quite what you think it is; (==) is not a constructor, therefore it is a *variable*. It's exactly the same problem as a = 5 -- ... foo a = 3 -- this does NOT compare with the previous value of a; it's identical to the next line! foo x = x Just as with the above, the normal way to do it would be to use a guard... but functions don't have an Eq instance, and *can't* have one. How do you meaningfully compare them? And for a typeclass function like (==), do you want (==) instantiated for Int to compare equal to (==) instantiated for Integer? Does a native-compiled function compare equal to an interpreted function? Remember referential transparency; the concept of comparing pointers used in some languages is not applicable to Haskell. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Comparing functions
On Thu, Jul 11, 2013 at 2:11 PM, Vlatko Basic vlatko.ba...@gmail.comwrote:
The problem here isn't quite what you think it is; (==) is not a
constructor, therefore it is a *variable*. It's exactly the same problem as
a = 5
-- ...
foo a = 3 -- this does NOT compare with the previous value of a;
it's identical to the next line!
foo x = x
Hm, I thought it is a pattern match with constant, as in f ('a':xs) ==
I wonder what you'd make of this definition, then?
(*) `on` f = \x y - f x * f y
--
brandon s allbery kf8nh sine nomine associates
allber...@gmail.com ballb...@sinenomine.net
unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Comparing functions
On Thu, Jul 11, 2013 at 2:58 PM, Vlatko Basic vlatko.ba...@gmail.comwrote:
Hm, I thought it is a pattern match with constant, as in f ('a':xs) ==
I wonder what you'd make of this definition, then?
(*) `on` f = \x y - f x * f y
According to the enlightenment above, I'd say (*) is a variable that holds
some function/operator that is applied on (f x) and (f y), not the
multiplication, right?
Correct. But if it's a variable there, why would you expect it to be a
constant in a different pattern?
--
brandon s allbery kf8nh sine nomine associates
allber...@gmail.com ballb...@sinenomine.net
unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghci ghc - JS (Emscripten)
On Wed, Jul 3, 2013 at 6:26 AM, B B blackbox.dev...@gmail.com wrote: Could you please answer one additional question - why you, while creating GHCJS didn't base on emscripten? Why haven't you patched it and created custom solution? I'd like to point out that the LLVM code from GHC is CPS-transformed, and this makes it a nightmare to work with. Already the LLVM optimizer pretty much fails to do anything: optimizing CPS-transformed code is well-nigh impossible without knowing what the pre-transformation code was, which means a GHC-specific optimizer is necessary, or some way to communicate the code's structure (LLVM actually supports annotations for this, but current GHC doesn't generate them; I also would expect those annotations to go only so far without GHC-specific tweaks to LLVM, and in fact I am under the impression such tweaks have been proposed for inclusion in LLVM). Similarly I would expect that generating any sort of sensible Javascript would require something fairly tightly tied to GHC; otherwise the output's going to have horrible performance because it's not going to understand the input and will fall back to the slowest but most general translation. (If it even has such a fallback, instead of simply failing on code that it doesn't recognize.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Installing Z3 on OS X 10.8.4 ( Off topic )
On Mon, Jul 1, 2013 at 8:34 AM, Johannes Waldmann waldm...@imn.htwk-leipzig.de wrote: and note that the install script says: Z3 shared libraries were installed at /usr/local/lib, make sure this directory is in your LD_LIBRARY_PATH environment variable. Only applicable on Linux (and setting the OS X equivalent of LD_LIBRARY_PATH is an absolutely wonderful way to break your system). OS X compiles full paths to shared objects into binaries, and provides a tool to change them if the need arises (install_name_tool). -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] question about indentation conventions
On Mon, Jul 1, 2013 at 3:43 AM, Tom Ellis tom-lists-haskell-cafe-2...@jaguarpaw.co.uk wrote: is OK but f (g x y z) is not. It seems to me that this means f x1 x2 x3 x4 is not. The OP was initially asking about this situation. If you wrote that in a do, the compiler would insert a () between the two lines. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] question about indentation conventions
On Mon, Jul 1, 2013 at 9:56 AM, Tikhon Jelvis tik...@jelv.is wrote: I've thought about writing an automatic indenting tool for Haskell (or, more accurately, a pretty-printer) for another project I have, and this is the main thing that threw me off. While automatic indentation might make sense for less expressive languages (Google Go being an extreme example), I think it would be too constraining for Haskell. After all, in reasonable code, chances are that similar constructs end up meaning wildly different things (especially with the advent of pervasive embedded DSLs), so the code itself is a poor indicator of its own structure. One might look at the history of the indentation modules for Emacs haskell-mode. Short version: they gave up, tab iterates through the possibilities because it's quite impossible to know which one is correct without a *semantic*, not just syntactic, understanding of the code. (Which, when you think about it, is pretty much par for the Haskell language definition. See also the literally impossible brace insertion rule of Haskell98.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Spam on list??
On Mon, Jul 1, 2013 at 11:19 AM, Vlatko Basic vlatko.ba...@gmail.comwrote: Anybody else getting this spam emails from j...@eukor.com every time a message is sent to Cafe? Yes, and I'm hoping a list admin steps in soon. The irony is, it's their *anti*spam filter. They decided to use one of those obnoxious whitelisting systems that requires all senders to register with it before it will pass on their mail... but didn't exclude mailing lists from this. Mailing lists, of course, can't authenticate, so they're sending all these image-heavy please whitelist yourself messages in Korean to the list submission address *and* not seeing any actual list traffic. This is one of the reasons I sometimes wish that use of an active spam whitelist like this were grounds for disabling the user's email account. They can't even tell what kind of mess they're making. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] tangential request...
On Sat, Jun 22, 2013 at 9:49 PM, Michael Orlitzky mich...@orlitzky.comwrote: On 06/22/2013 01:28 PM, Mark Lentczner wrote: 3) Do not resize the terminal window and 5) Take a screen shot of the whole terminal window are mutually exclusive? No, he wants a window shot, not a whole-screen shot. What *is* inconsistent is that do not resize presumably take it at its natural size. Users of tiling window managers need not apply -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Strange cabal failure
On Tue, Jun 18, 2013 at 1:57 PM, Jacques Carette care...@mcmaster.cawrote: In trying to install the lens package, it eventually tries to install transformers-compat-0.1.1.1 which in turn depends on transformers-0.3.0.0 -- however that asksk for transformers-0.3.0.0-**3006d6ea13a2c10770bffd4de7a96d**c9 which 1) is weird, and 2) doesn't exist!' What gives? The large blob at the end is an ABI hash which is computed when you install a package. So it would appear that you had transformers-0.3.0.0 installed and then removed it, but it's still indexed for some reason. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] opengl type confusion
On Sun, Jun 16, 2013 at 4:03 PM, bri...@aracnet.com wrote: Changing the declaration to GLdouble - GLdouble - GLdouble - IO() and using (0.0::GLdouble) fixes it, and I'm not clear on why it's not automagic. There are many times I see the Haskell never automagics types in that context; if it expects GLdouble, it expects GLdouble. Pretending it's Double will not work. It would in the specific case that GLdouble were actually a type synonym for Double; however, for performance reasons it is not. Haskell Double is not directly usable from the C-based API used by OpenGL, so GLdouble is a type synonym for CDouble which is. compiler doing type conversion an numerican arguments although sometimes the occasional fracSomethingIntegralorOther is required. I presume the reason the type specification for numeric literals is because there is no defaulting (and probably can't be without introducing other strange type issues) for GLdouble. In any case, the very fact that you refer to automagic and type conversion indicates that you don't really have an understanding of how Haskell's numeric types work; this will lead you into not only this kind of confusion, but worse problems later. In particular, you're going to get into dreadful messes where you expect Haskell to transparently deal with strange combinations of numeric types as if Haskell were (almost-typeless) Perl or something, and you'll have real trouble getting that code to work until you sit down and figure out how strong typing and Haskell's numeric typeclasses interact. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] opengl type confusion
On Sun, Jun 16, 2013 at 4:42 PM, bri...@aracnet.com wrote: On Sun, 16 Jun 2013 16:15:25 -0400 Brandon Allbery allber...@gmail.com wrote: On Sun, Jun 16, 2013 at 4:03 PM, bri...@aracnet.com wrote: Changing the declaration to GLdouble - GLdouble - GLdouble - IO() and using (0.0::GLdouble) fixes it, and I'm not clear on why it's not automagic. There are many times I see the I presume the reason the type specification for numeric literals is because there is no defaulting (and probably can't be without introducing other strange type issues) for GLdouble. What I was thinking about, using a very poor choice of words, was this : *Main let a = 1 *Main :t a a :: Integer *Main let a = 1::Double *Main a 1.0 *Main :t a a :: Double *Main so normally 1 would be interpreted as an int, but if I declare 'a' a Double then it gets promoted to a Double without me having to call a conversion routine explicitly. That seems automagic to me. No magic involved, although some automation is. Take a look at the `default` keyword in the Haskell Report (this is the defaulting I mentioned earlier). http://www.haskell.org/onlinereport/haskell2010/haskellch4.html#x10-790004.3.4 The default `default` is `default (Integer, Double)` which means that it will try to resolve a numeric literal as type Integer, and if it gets a type error it will try again with type Double. You should use this same mechanism to make numeric literals work with OpenGL code: neither Integer nor Double will produce a valid type for the expression, but at the same time the compiler cannot infer a type because there are two possibilities (GLfloat and GLdouble). You could therefore add a declaration `default (Integer, Double, GLdouble)` so that it will try GLdouble to resolve numeric literals when neither Integer nor Double will work. How can I simply declare 0.0 to be (0.0::GLdouble) and have the functional call work. Doesn't a conversion have to be happening, i.e. shouldn't I really have to do (realToFrac 0.0) ? The first part I just answered. As to the second, a conversion *is* happening, implicitly as defined by the language; the question being, to what type. A numeric literal has type (Num a = a), implemented by inserting a call to `fromIntegral` for literals without decimal points and `fromRational` for others. But the compiler can't always work out what `a` is in (Num a = a) without some help (the aforementioned `default` declaration). -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automating Hackage accounts
On Thu, Jun 13, 2013 at 10:48 AM, Niklas Hambüchen m...@nh2.me wrote: As for the user account creation and uploading packages you don't own, Hackage 2 (any day now) has fixes for both. Does Hackage 2 have SSL at least for the web interface? Doesn't look like it. :( -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to write a pure String to String function in Haskell FFI to C++
On Sun, Jun 2, 2013 at 7:22 PM, Ting Lei tin...@gmail.com wrote: In particular, I wanted to avoid having an IO in the return type because introducing the impurity (by that I mean the IO monad) for this simple task is logically unnecessary. All examples involing Anything that comes into or goes out of a Haskell program is in IO, period. If you have an FFI function which is guaranteed to not change anything but its parameters and those only in a pure way, then you can use unsafeLocalState to hide the IO; but claiming that when it's not true can lead to problems ranging from incorrect results to core dumps, so don't try to lie about it. a C string I have seen so far involve returning an IO something or Ptr which cannot be converted back to a pure String. Haskell String-s are *not* C strings. Not even slightly. C cannot work with Haskell's String type directly at all. Some kind of marshaling is absolutely necessary; there are functions in Foreign.Marshal.String that will marshal Haskell String-s to and from C strings. (String is a linked list of Char, which is also not a C char; it is a constructor and a machine word large enough to hold a Unicode codepoint. And because Haskell is non-strict, any part of that linked list can be an unevaluated thunk which requires forcing the evaluation of arbitrary Haskell code elsewhere to reify the value; this obviously cannot be done in the middle of random C code, so it must be done during marshaling.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to write a pure String to String function in Haskell FFI to C++
On Sun, Jun 2, 2013 at 8:01 PM, Thomas Davie tom.da...@gmail.com wrote: On 2 Jun 2013, at 16:48, Brandon Allbery allber...@gmail.com wrote: (String is a linked list of Char, which is also not a C char; it is a constructor and a machine word large enough to hold a Unicode codepoint. And because Haskell is non-strict, any part of that linked list can be an unevaluated thunk which requires forcing the evaluation of arbitrary Haskell code elsewhere to reify the value; this obviously cannot be done in the middle of random C code, so it must be done during marshalling.) I'm not convinced that that's obvious – though it certainly requires functions (that go through the FFI) to grab each character at a time. I think you underestimate the complexity of the Haskell runtime and the interactions between it and the FFI. Admittedly it is probably not obvious in the sense of anyone can tell without knowing anything about it that it can't possibly work, but it should be at least somewhat obvious to someone who sees why there needs to be an FFI in the first place that the situation is not trivial, and that they probably should not blindly assume that the only reason one can't just pass Haskell values directly to C is that some GHC developer was feeling lazy at the time. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Different answers on different machines
On Sat, Jun 1, 2013 at 1:55 PM, nadine.and.he...@pobox.com wrote: a Dell laptop and a desktop. I compiled this message with ghc -O2 --make ex429.lhs and ran it on each machine. On the Dell I get: 136342232 ./ex429 8.66s user 0.02s system 99% cpu 8.695 total When I run this exact same file on the desktop, I get: 98792821 ./ex429 6.50s user 0.03s system 99% cpu 6.537 total Which happens to be the right answer. But WHY is the output from the Dell different? (hardware description elided) You're missing one piece of information: do you have the 32-bit or the 64-bit ghc installed on each machine? -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] using a win32 dll (Happy too soon)
On Thu, May 30, 2013 at 3:15 AM, Kees Bleijenberg k.bleijenb...@lijbrandt.nl wrote: argument. The dll is in the PATH. I don't understand why it needs the -L argument. I'll figure this out later. If I use -lglasPng.dll (additional .dll) it doesn't work either. Unix has standard places to install and search for libraries; Windows doesn't, and almost every library that doesn't come with your build system will need at least one -L option to tell the linker where to find it. As I mentioned in my first message, it looks for multiple file names with -l: first it tries a .dll, then it tries a .lib (static library or import library for older DLLs). It does this mechanically; if you also include the .dll suffix, then it looks for library.dll.dll and library.dll.lib, which is almost certainly wrong. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] using a win32 dll (Happy too soon)
On Thu, May 30, 2013 at 11:46 AM, Kees Bleijenberg k.bleijenb...@lijbrandt.nl wrote: Brandon, thanks again for your explanation Are you sure about the non existing search order for dynamic loaded dll’s? I.e. http://msdn.microsoft.com/en-us/library/windows/desktop/ms682586(v=vs.85).aspx#standard_search_order_for_desktop_applicationssays there is a search order, starting with the current directory (I think). There is a search order. What I said is that there are no standard locations to install things. That is, every library package stows stuff in its own directory structure and no compiler can possibly know all the places it needs to look to find every library off in its own directory. I don’t understand why the linker needs to see the dll anyway. Because it's better to catch that symbol doesn't exist at build time instead of throwing an ugly error at runtime, among other things. possible in Delphi. Is Haskell dynamic loading more limited? There are ways to do that kind of dynamic linking; this is not one of them. C and C++ don't automatically dynload the way you're thinking either, because you should test for the DLL you're distributing (you are distributing it, right, not forcing the end user on a wild goose chase to find their own copy of the DLL, hoping it's the right/compatible version, and figure out where to put it so your program will run?) being the right one *when you build the program*, not defer that test until it is run. If you think about it, this is very similar to doing your type checking at compile time instead of runtime. If you want lazy type checking, why are you using Haskell? If you want lazy library checking, why are you using a compiler? -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] using a win32 dll (Happy too soon)
On Wed, May 29, 2013 at 9:40 AM, Kees Bleijenberg k.bleijenb...@lijbrandt.nl wrote: If I compile with ghc --make testGlasPng.hs –lglasPng I get: ….\ld.exe: cannot find –lglasPng. Collect 2: ld returned 1 exit status. ** Ld can’t find lglasPng (with the l in front, does it trim the l?). Why? Okay I try It's reproducing the thing passed to it, rather than outputting both the dll and implib versions that it actually looks for. Same happens on unixlikes where it's looking for a .so/.dylib/whatever or a .a. ghc --make testGlasPng.hs –Lpath to glasPng.dll I get: Not quite right; -L identifies a *directory* to search, then you must specify the actual filename afterward. testGlasPng.o: fake: (.text + 0x82) :undefined reference to ‘getPngVersion@0’. I think it has found the This just means it can't find the symbol; it does not mean it necessarily found the DLL. I run ghc on a 64 bits computer. The dll is 32 bits. Is that the problem? That can certainly be a problem, yes, and is likely why it wasn't found with the first one. But it's not so much what kind of machine you are on, as what kind of ghc you are using: a 64-bit ghc cannot link 32-bit libraries, and vice versa. But a 32-bit ghc and toolchain will work fine on a 64-bit system, aside from not linking 64-bit DLLs. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] list comprehension doesn't work
On Tue, May 14, 2013 at 11:17 AM, John knowledge1...@gmail.com wrote: listPairs = [(a*b, y) | a - [0..], b - [0..], (a*b) 5, (a*b) 500, (y*y) 1001, mod y x == 0] Now I have it as you said, however the compiler complains about all y and x and says they are NOT in scope. Why is it so? I can't see any problem with that... I don't see any definitions of x or y there. (Note that you have replaced x with a*b.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghci: Difference in garbage collection etc. between REPL and function
On Wed, May 8, 2013 at 9:54 PM, Niklas Hambüchen m...@nh2.me wrote: If I run these steps one by one in ghci, garbage ends up in my handle as expected. However, if I let main = do ... this whole block in order to pack it in a test case, it does not happen, neither in ghci nor ghc. ghci is in many ways like an endless (or at least until :l/:r) do-block. In particular, the handle remains in scope after you run your commands at the prompt, so it is not garbage collected. If you enclose it into its own do block, this introduces local scope and the handle goes out of scope and is garbage collected at the end. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghci: Difference in garbage collection etc. between REPL and function
On Thu, May 9, 2013 at 10:19 AM, Niklas Hambüchen m...@nh2.me wrote: On 09/05/13 20:50, Brandon Allbery wrote: ghci is in many ways like an endless (or at least until :l/:r) do-block. In particular, the handle remains in scope after you run your commands at the prompt, so it is not garbage collected. If you enclose it into its own do block, this introduces local scope and the handle goes out of scope and is garbage collected at the end. I am not sure how the handle is relevant - I do not expect it to garbage collected before the close or rely on that, and my problem happens earlier already. You said 'garbage in the handle'... but in any case it applies to all the bindings, not just to that one. Generalize. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Fwd: Backward compatibility
On Sun, May 5, 2013 at 7:55 AM, Raphael Gaschignard dasur...@gmail.comwrote: Forgive me if I'm wrong, but I feel like I've seen such suggestions in GHC errors before. If so, does that mean there's some sort of mechanism in the compiler already in place for such error recognition? Like some simple pattern stuff? If not, I think that it might not be bad to consider this stuff (misused packaged, changed semantics that create compiler errors), and to put something into place for future modifications. This could make it a lot easier to deal with unmaintained code. There's some very limited capability now; the GHC folks are tossing around ideas for something more general like that. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] runhaskell flags: What is going on?
Bleh, I could have sworn that thing had a real usage message at some point... which means there is in fact a problem and you should file a bug against runhaskell. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Backward compatibility
On Fri, May 3, 2013 at 5:30 AM, Adrian May adrian.alexander@gmail.comwrote: How about this: can you guys give me a detailed example of a justified deprecation: one so extremely obviously called for that even I would agree. I just want to understand the kind of logic that's applied over these things. This might not be possible because your notion of a justified change may not align with other people's. IIRC the removal of the Show constraint on Num was driven by type level natural numbers? which matter to the type hackers but not to someone whose main concern is getting an unmaintained web interface running. (OTOH it also may not have any effect on said web server, since it mostly affected people who take the somewhat risky action of defining their own Num instances; I suspect the exceptions change would have more impact on web stuff.) As for the exceptions stuff, that was a multi-step change. Exception handling was somewhat unprincipled and came in two forms, which used the same function names but in different ways. There was support for IO exceptions in the Prelude and conflicting support for general exceptions, which behaved somewhat differently when handed an IO exception, in Control.Exception. One key behavior was that you had to handle all exceptions or none at all; the only way to choose specific exceptions was to handle all of them, inspect the exception object, and rethrow if it wasn't one you wanted to handle. And inspecting the exception object to see what it had in it could be tricky at times, because there wasn't much guidance with respect to user defined exceptions and some library exceptions did things slightly differently from the ones in the base. The exception cleanup made IO exceptions and other exceptions behave consistently and got rid of the conflicting definitions. This did require source changes, as anyone relying on the Prelude exceptions had to add an import of Control.Exception and anyone using old-style exceptions generally had to add a type annotation to their handler; more ideally, they'd rewrite their exception code to handle specific exceptions or exception classes instead of poking at the exception object to determine whether it was one they cared about or not --- but this was not necessary to get older code running again, only the added type annotation was necessary. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] runhaskell flags: What is going on?
On Fri, May 3, 2013 at 10:35 AM, Niklas Hambüchen m...@nh2.me wrote: runhaskell -fno-warn-unused-matches Myfile.hs [some compile error] runhaskell -fno-warn-unused-matches Myfile.hs [no output whatsoever but exit code 127] runhaskell -asdf Myfile.hs ghc: unrecognised flags: -asdf runhaskell -fasdf Myfile.hs [no output whatsoever but exit code 127] Not sure if that's how it should work or missing error reporting? If you type just 'runhaskell' you will get an error message which explains what is going on. (The short version is, -f has multiple meanings; some of them apply to runhaskell, and some to the underlying ghc.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Backward compatibility
On Fri, May 3, 2013 at 10:54 AM, Guy guytsalmave...@yahoo.com wrote: http://hackage.haskell.org/**trac/ghc/wiki/**DefaultSuperclassInstanceshttp://hackage.haskell.org/trac/ghc/wiki/DefaultSuperclassInstances I'm surprised that the various superclass proposals haven't got more attention, seeing as it would allow for this kind of class hierarchy clean-up without breaking lots of code. IIRC they've been tried and found to actually cause more backward compatibility issues than they solve because there are so many packages which have created their own instances, and nobody's found a workaround that doesn't either do that or lead to bizarre type errors. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Backward compatibility
On Thu, May 2, 2013 at 1:27 AM, Adrian May adrian.alexander@gmail.comwrote: Let's face it: this decision to change the default syntax in GHC7 means that right now Haskell looks about as stable as Ruby on Rails. I just tried to use Flippi. It broke because of the syntax change so I tried WASH. I couldn't even install it because of the syntax change. I persisted for a while but gave up because getPackageId doesn't exist in any form at all anymore. This was only the install script: what would WASH itself have in store for me to get my brain around? I'm going to give you the flip side of this one. I've been active in the Perl community (admittedly in something of an off and on fashion for health reasons) for years. Perl 5 is in some ways the epitome of maintain backward compatibility: there is a lot of Perl code out there that was written under Perl 4 or earlier. (cpanel, I'm looking at you. Among others. I recently got to debug some code related to someone's RADIUS server that looked like it hadn't been touched since perl3.) And this is the direct cause of the Perl ecosystem being a sewer. Nobody is willing to take the step of making Perl default to the eminently sane behavior of checking for invalid inputs, because it will break too much existing (already horribly broken, in reality) code. Nobody will risk disabling the walking security hole and encouragement of sloppy, buggy code that is Perl's 2-argument open(). (If you ever wondered why Perl 6 decided to throw out source compatibility, here's your reason.) The Haskell98 ecosystem wasn't nearly that bad, but maintaining compatibility with it did prevent fixing various flaws in things like exception handling. Between the two, I'd rather see older code broken in the name of current code actually working correctly. And in Haskell I get a lot of help from the compiler to bring that older code up to date. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Backward compatibility
On Thu, May 2, 2013 at 10:36 AM, Adrian May adrian.alexander@gmail.comwrote: I think you're missing the point of the platform! I suppose I did miss the point of the platform: I was trying to build it, which requires at least part of the Having to build it already indicates that something is wrong, unless you're porting to an unsupported OS/hardware. platform. As I say, the reason I was trying to build it was that I wrongly blamed the ubuntu package for That said, may I point out that the Ubuntu packages *are* broken? They shipped a mangled Platform which can't be relied on for much; instead of a well-tested set of packages, they took a good Platform and replaced bits with minimal testing. Yes, this has actually caused problems for people. Yes there are times when something has to change. I acknowledged that in my original post. But I see no evidence whatsoever that anybody in control of Haskell is holding fire even on things as innocent as getPackageId or as ubiquitous as the prelude. I'm not asking for the opposite extreme of conservatism, just a bit of common sense instead of this bloodbath. You're assuming here that someone deliberately targeted your favorite pet. I don't know the details but I VERY STRONGLY doubt anyone said oh, we should break that function. But I ALSO find it likely that it was the victim of something sufficiently pervasive that the options were break it or live with something else being broken forever, just like Perl vs. cpanel! This, sadly, is the real world. The holy grail of fixing bugs without breaking any program ever anywhere is impossible, and even fix this bug without breaking many other programs is extremely unlikely. Your choices are this, or Perl/PHP we do not dare fix bugs or misdesigns because someone's pet program will die. (Other examples of this: - Python 3. Note how many existing Python packages still require Python 2. - The C and C++ standards are increasingly Byzantine due in large part to backward compatibility issues; but I'm guessing from your complaints that this is your ideal model because old programs still work. Lucky you, you can happily pretend that it's because they have found some magical way to do the fundamentally impossible --- right up until reality bites back. ) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why were datatype contexts removed instead of fixing them?
On Sun, Apr 28, 2013 at 3:59 AM, harry volderm...@hotmail.com wrote: Dan Doel dan.doel at gmail.com writes: However, another thing to consider is that getting rid of data type contexts was accepted into the language standard. ... which means that implementers should be free to fix data type contexts however they like, as they are now complier extensions which won't conflict with standard Haskell. Except that people do build older programs with newer Haskell compilers, and it's bad to repurpose a syntax like that because it leads to strange errors. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Request for help: Recompile of ghc producing ...-ghc7.4.2.sos, which break project builds.
On Sat, Apr 27, 2013 at 11:47 AM, David Banas capn.fre...@gmail.com wrote:
dbanas@dbanas-lap:~/prj/AMI-Tool$ make
rm -f libami.so
ghc -o libami.so -shared -dynamic -package parsec -lHSrts -lm -lffi -lrt
AMIParse.o AMIModel.o ami_model.o ExmplUsrModel.o Filter.o
dbanas@dbanas-lap:~/prj/AMI-Tool$
However, I'm a little confused as to why the -package parsec isn't
triggering the same issue, since the parsec dynamic libraries were given
the same -ghc7.4.2 suffix:
That would be because the parsec library contains the correct invocation
already, but above you are telling the linker to look for libHSrts.{so,a}
with the explicit -l option. You would need to change it to
```-lHSrts-ghc7.4.2```.
Perhaps ghc needs an option to include the correct runtime support
libraries in this case; certainly, having to specify all of those in the
build command is ugly and fragile even without mangled shared object names.
--
brandon s allbery kf8nh sine nomine associates
allber...@gmail.com ballb...@sinenomine.net
unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why were datatype contexts removed instead of fixing them?
On Thu, Apr 25, 2013 at 6:38 AM, harry volderm...@hotmail.com wrote: If I understand correctly, the problem with datatype contexts is that if we have e.g. data Eq a = Foo a = Foo a the constraint Eq a is thrown away after a Foo is constructed, and any method using Foos must repeat Eq a in its type signature. Why were these contexts removed from the language, instead of fixing them? As I understand it, it's because fixing them involves passing around a dictionary along with the data, and you can't do that with a standard declaration (it amounts to an extra chunk of data that's only *sometimes* wanted, and that sometimes complicates things). GADTs already have to pass around extra data in order to support their constructors and destructors; and, being new and not part of the standard, they don't have backward compatibility or standards compatibility issues, so they can get away with including the extra dictionary without breaking existing programs. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] exp implementation
On Thu, Apr 11, 2013 at 1:38 AM, Christopher Howard christopher.how...@frigidcode.com wrote: Hi. For my own learning, I wanted to see how the exp function is implemented in GHC. I have GHC 7.4.1 source code open, but I'm having trouble figuring out which file the actual function definition is in. I see expFloat(F# x) = F# (expFloat# x) expFloat# is likely a primop; good luck Primops aka primitive operations are generally implemented in the compiler backend as assembly language or Cmm code. Untangling that part of ghc makes my head swim. . -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal-install 1.16.0.2 on Mac
On Thu, Apr 11, 2013 at 1:19 AM, Richard A. O'Keefe o...@cs.otago.ac.nzwrote: On 11/04/2013, at 12:56 PM, Brandon Allbery wrote: Xcode 4.2 and on do not use /Developer at all. You have an older Xcode on your system somehow, which does not understand newer object files; you should remove the entire /Developer tree. (Xcode, in order to be distributable via the App Store, is completely self-contained in /Applications/Xcode.app.) Unfortunately, I cannot. I _am_ able to install stuff, but uninstalling generally gives me problems, and removing /Developer is something I'm not allowed to do. I think you need to discuss that with whoever made that dictum; requiring that a system be broken is not generally a good idea. Many software packages will find it and use outdated programs or frameworks as a result. It really needs to not be there at all. (Newer Xcode should actually complain and tell you to run the removal script on startup, because its presence can even break Xcode under some circumstances.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal-install 1.16.0.2 on Mac
On Thu, Apr 11, 2013 at 7:41 PM, Richard A. O'Keefe o...@cs.otago.ac.nzwrote: The basic problem is that the University has a strict policy that academic staff must not have root access on any machine that is connected to the University network. I was given an administrator account so that I could resume the printer and install (some) stuff, but /Developer is owned by root, and I will be given root access on the Greek Calends. I would have thought that many organisations would have similar policies. Well, yes (I was one of those admins, although not at your university, for many years), but if they are installing machines with both Xcode 4.6 under /Applications and Xcode 4.1 or earlier under /Developer, they are installing broken machines that will fail to build many packages and where Xcode may malfunction. /Developer should not exist on a machine with Xcode 4.2 or later installed, at all. You should contact an administrator about this and have them fix both installed machines and their installation images or maintenance routines (whatever they went with for OS X). sudo /Developer/Library/uninstall-devtools --mode=all If they need an official reference on this, I can dig up the relevant Apple knowledge base article. On 12/04/2013, at 2:44 AM, Brandon Allbery wrote: (Newer Xcode should actually complain and tell you to run the removal script on startup, because its presence can even break Xcode under some circumstances.) 4.6.1 was the latest available in March when I installed it, and it _didn't_ complain or tell me to run any removal script. I have heard that it is sometimes inconsistent about this; sadly, just because it didn't notice the older version doesn't mean the older version won't cause breakage. (As you saw.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bug in Network package
On Wed, Apr 10, 2013 at 3:26 AM, Florian Hofmann fhofm...@techfak.uni-bielefeld.de wrote: I might be mistaken, but is there a bug in the Show instance of PortNum? Not a bug, an annoying misdesign (IMO). A PortNum is actually in network byte order. If you extract it, you get the original port; if you simply show it, you see it byteswapped on little-endian platforms. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Automated Differentiation of Matrices (hmatrix)
On Wed, Apr 10, 2013 at 12:39 PM, Dominic Steinitz domi...@steinitz.orgwrote: interactive:1:6: Could not deduce (repa-3.2.3.1:Data.Array.Repa.Eval.Elt.Elt (ad-3.4:Numeric.AD.Internal.Types.AD s a)) DANGER WILL ROBINSON! It's showing package names+versions on the types; this usually means you have multiple versions of those packages installed, and ghc / ghci is confused as to which one to use. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal-install 1.16.0.2 on Mac
On Wed, Apr 10, 2013 at 8:36 PM, Richard A. O'Keefe o...@cs.otago.ac.nzwrote: /Developer/usr/bin/strip: object: /home/cshome/o/ok/.cabal/bin/cabal malformed object (unknown load command 15) Xcode 4.2 and on do not use /Developer at all. You have an older Xcode on your system somehow, which does not understand newer object files; you should remove the entire /Developer tree. (Xcode, in order to be distributable via the App Store, is completely self-contained in /Applications/Xcode.app.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] llvm-3.0.1.0 installation on Mac
On Mon, Apr 8, 2013 at 1:32 AM, Luke Evans l...@eversosoft.com wrote: Unfortunately, it looks like /Library/Frameworks/GHC.framework/Versions/7.4.2-x86_64/usr/lib/ghc-7.4.2/libffi.dylib is pointing to the dodgy library too, e.g.: otool -L /Library/Frameworks/GHC.framework/Versions/7.4.2-x86_64/usr/lib/ghc-7.4.2/libffi.dylib /Users/ian/zz64/ghc-7.4.2/libffi/build/inst/lib/libffi.5.dylib (compatibility version 6.0.0, current version 6.10.0) /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 159.1.0) Not sure what to patch the first reference in that one to. To itself; that's actually the internal reference that gets compiled into the others, and as such is the actual source of the problem. (In an ELF shared object, that would be the soname. Note that it *must* be a full path on OS X, unlike Linux/ELF.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] llvm-3.0.1.0 installation on Mac
On Mon, Apr 8, 2013 at 12:10 AM, Luke Evans l...@eversosoft.com wrote: Unfortunately, it looks like my cabal build failure occurs in a temporary and very short-lived directory. So presumably the dodgy FFI gets copied into there from elsewhere. I wonder if I can find the source... It's running an executable it seems to have built to generate something else for the build, so I suspect you are in fact seeing the ghc bug and you should fix the ghc reference. If you installed the official HP package, you need to find libHSrts-ghc7.4.2.dylib somewhere under /Library/Haskell and use install_name_tool on that. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why is Cont out of scope?
On Tue, Apr 2, 2013 at 8:37 PM, Daryoush Mehrtash dmehrt...@gmail.comwrote: I am trying to use the Cont in Control.Monad.Cont but it seems to be missing Prelude import Control.Monad.Cont Prelude Control.Monad.Cont :t Cont It's gone; try cont (lowercase). mtl2 replaced the old standalone monads with monad transformers over the Identity monad (so Cont is a type alias for ContT Identity); however, it's not possible to create data constructors for type aliases, so the Cont data constructor is gone and a cont smart constructor has taken its place. Prelude Control.Monad.Cont :t cont cont :: ((a - r) - r) - Cont r a The same is true of State, Reader, and Writer. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Make a DSL serializable
On Mon, Mar 25, 2013 at 8:53 AM, Corentin Dupont corentin.dup...@gmail.comwrote: Workflow is impressive! I didn't know you could serialize IO states/computations. In certain constrained cases you can. General case, as I said earlier, is kinda impossible without serializing the entire machine state. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Make a DSL serializable
On Sun, Mar 24, 2013 at 4:16 PM, Corentin Dupont corentin.dup...@gmail.comwrote: Hi Daniel, in my game the handlers are supplied by the players as part of little programs that they submit. An haskell interpreter is reading the program code submitted and inserts it in the game. So there is an infinite number of handlers... You might store both the compiled code and the originally submitted code, and serialize the latter in a form that restart can recompile. I don't think that can be any less safe than the original submission/compilation/insertion. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Make a DSL serializable
On Sun, Mar 24, 2013 at 5:44 PM, Corentin Dupont corentin.dup...@gmail.comwrote: But I always bothered me that this state is not serializable... I am not quite sure how to respond to that. You seem to be asking for magic. That kind of state has never been sanely serializeable. Not in Haskell, not anywhere else. The usual hack is to dump an entire memory image to disk, either as an executable (see gcore and undump; also see how the GNU emacs build dumps a preloaded emacs executable) or by dumping the data segment as raw bytes and reloading it as such (which doesn't work so well in modern demand paged executables; it can work better with a virtual machine environment, and various Lisp and Smalltalk implementations dump and reload their raw VM images this way). I would not be surprised if what you seem to be asking for turns out to be yet another guise of the halting problem. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Enumerating functions at runtime
On Sat, Mar 23, 2013 at 11:26 PM, Luke Evans l...@eversosoft.com wrote: I'm curious about using Haskell for metaprogramming. It looks like I can dynamically compile, load and run some Haskell with the plugins package. Actually I've briefly tried this and it seems to work for some simple cases at least. Now I would like to be able to enumerate precompiled public functions in modules that I might use as building blocks in such dynamic compilation. So far I'm not seeing anything that does this directly. Can anyone provide some pointers? I'm not aware of any canned solutions, but one way you could do it is to enumerate the symbol table of a compiled module and z-decode symbols; functions get their types z-encoded into their symbol table names. A more likely useful way is to extract them from the .hi file; there should be functions in ghc-api and likely in hint to do this, since the compiler must do so as part of importing a module; or at worst, you can use ghc -print-iface to decode a .hi file to text and extract the information that way. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Compiled program using OpenGL fails to trigger GPU switch on Mac, but works in GHCi
On Wed, Mar 20, 2013 at 9:02 AM, Jesper Särnesjö sarne...@gmail.com wrote: This solution seems to work perfectly for me. Since the foreign code is allowed to run uninterrupted, the GPU switch happens, and since the GUI actions stay on the main thread, the program's window responds to keyboard and mouse input correctly. If that's correct, then I think you have found a bug in the GHC runtime: my understanding is that the timers should be disabled while foreign code is running, specifically to avoid confusing code that has no clue that there is another runtime involved. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Specialized Computer Architecture - A Question
On Mon, Mar 18, 2013 at 4:31 PM, OWP owpmail...@gmail.com wrote: Let me rephrase that, of course they will survive politically. People built these tools and if built, they will be use but will they survive efficiently? In the future, if a particular specialized architecture is somewhat better than the rest on it's own merit for a particular need while the stock architecture is reaching a point of low returns for all the energy put into it - could the specialized architecture reach a point where it becomes useful? Could there be a competitive advantage to specialized architecture if Moore's Law were to go away? There is now, in some narrow specializations. GPUs and DSP come to mind --- while both are also done on commodity CPUs to some extent, the specialized architectures are used where speed is of the essence. (DSP started out on specialized architectures, but many commodity uses are on commodity architectures these days, reserving the specialized ones to those niches that require them.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Compiled program using OpenGL fails to trigger GPU switch on Mac, but works in GHCi
On Sun, Mar 17, 2013 at 7:58 PM, Jason Dagit dag...@gmail.com wrote: On Sat, Mar 16, 2013 at 6:53 PM, Jesper Särnesjö sarne...@gmail.comwrote: To be clear, I think this isn't really an OpenGL problem, but rather one related to FFI or event handling. If anyone could explain to me,The release notes for 7.0.1 said this about that flag: There is a new -fno-ghci-sandbox flag, which stops GHCi running computations in a separate thread. In particular, this is useful for GLUT on OS X, which only works if being run on the main thread. Worth noting is that Jesper said it *works* in ghci, and fails when compiled -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Overloading
On Tue, Mar 12, 2013 at 1:52 PM, Carlos Camarao carlos.cama...@gmail.comwrote: Sorry, I think my sentence: To define (+) as an overloaded operator in Haskell, you have to define and use a type class. is not quite correct. I meant that to define any operator in Haskell you have to have a type class defined with that operator as member. What? An operator is just an infix function, taken from the set of symbols. Any function can be an operator (and is, via `func` syntax). No typeclass is required to define a random operator. What did you really mean to say there? -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal install oddities
On Tue, Mar 12, 2013 at 3:21 PM, Tycho Andersen ty...@tycho.ws wrote: Below is some sample output from a failing package: ps168825:~/playground$ cabal install network Resolving dependencies... Configuring network-2.4.1.2... configure: WARNING: unrecognized options: --with-compiler, --with-gcc checking build system type... x86_64-unknown-linux-gnu checking host system type... x86_64-unknown-linux-gnu checking for gcc... gcc checking whether the C compiler works... yes checking for C compiler default output file name... a.out checking for suffix of executables... checking whether we are cross compiling... configure: error: in `/tmp/network-2.4.1.2-28534/network-2.4.1.2': configure: error: cannot run C compiled programs. cabal install unpacks a package into /tmp in order to build it. My guess is your OS has /tmp mounted noexec. I don't know offhand how you override this in cabal. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] building darcs failed (Unable to link against the iconv library)
On Sun, Mar 3, 2013 at 10:21 AM, Dmitry Malikov malikov@gmail.comwrote: checking whether to use -liconv... setup: Unable to link against the iconv library. Failed to install darcs-2.8.4 cabal: Error: some packages failed to install: What is actually going on here? Iconv libraries already installed with libc6 package. Running ubuntu, cabal-install-1.16.0.2. Linux distinguishes between runtime and linkable libraries; you probably need to install the libc6-dev package to get the latter. (This is not a Haskell-specific issue; configure is using a C program to test the link.) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] building darcs failed (Unable to link against the iconv library)
On Sun, Mar 3, 2013 at 1:59 PM, Dmitry Malikov malikov@gmail.comwrote: On 03/03/2013 10:56 PM, Brandon Allbery wrote: On Sun, Mar 3, 2013 at 10:21 AM, Dmitry Malikov malikov@gmail.comwrote: checking whether to use -liconv... setup: Unable to link against the iconv library. What is actually going on here? Iconv libraries already installed with libc6 package. Linux distinguishes between runtime and linkable libraries; you probably need to install the libc6-dev package to get the latter. (This is not a Haskell-specific issue; configure is using a C But libc6-dev is already the newest version. Then you'll have to check config.log (this probably means doing the build manually with cabal unpack darcs and then running cabal install without a package name from the directory with the darcs.cabal file) to see what's going wrong. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal install ghc-mod installs 3 years old version
On Fri, Mar 1, 2013 at 12:08 PM, Albert Y. C. Lai tre...@vex.net wrote: On 13-03-01 05:10 AM, Malcolm Wallace wrote: Doesn't Cabal tend to install library packages under the .cabal folder? So blowing it away gets rid of the problematic ones. (And everything else.) You need to perform scientific experiments to refute that claim, then see my At least some versions of cabal-install do put the actual library install trees under .cabal/lib, then register them under .ghc. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Question about forkIO
On Thu, Feb 28, 2013 at 6:09 AM, C K Kashyap ckkash...@gmail.com wrote: Say I have a haskell function 'f' that does a forkIO and starts an action a. I create a DLL of this haskell code and inovke f from C. Can I expect the a to continue to run once f has returned to C? While you're off in C the I/O manager and garbage collector are suspended. Many C programs are not prepared to deal with the side effects of their operation, such as being interrupted by timer signals; moreover, it is not possible to have multiple handlers at the OS level for a signal, and C programs may want to use the signal handlers themselves. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: Nomyx 0.1 beta, the game where you can change the rules
On Wed, Feb 27, 2013 at 8:37 AM, Corentin Dupont corentin.dup...@gmail.comwrote: Hi Chris, Thanks! That's true for the user number. What should I do? Encrypt it? It's not that you have a user number, or even that it's accessible: it's that it's the entirety of access control, meaning that if the user changes it they can masquerade as another user. The correct solution is that a user should authenticate, which creates a session hash that you stash away and also send back to the user as a cookie so the browser will present it on accesses. Then you check that the presented hash is there and matches the session hash. These should expire periodically, requiring the user to log back in again. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parser left recursion
On Sun, Feb 24, 2013 at 6:31 AM, Martin Drautzburg martin.drautzb...@web.de wrote: Just a silly quick question: why isn't right-recursion a similar problem? Very roughly: Left recursion is: let foo n = n + foo n in ... Right recursion is: let foo 1 = 1; foo n = n + foo (n - 1) in ... In short, matching the tokens before the right recursion will constitute an end condition that will stop infinite recursion --- if only because you'll hit the end of the input. Left recursion doesn't consume anything, just re-executes itself. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Need urgent help with Network.tls
On Sat, Feb 23, 2013 at 1:58 PM, C K Kashyap ckkash...@gmail.com wrote: What I am really looking for is a small sample code that demonstrates how TLS package can be used to connect to a webserver or imapserver. TLS isn't actually SSL, despite SSL getting blessed as TLS 0.9. Various attempts at TLS-enabled web protocols have foundered, so you won't find much code to speak TLS to web servers. (SSL is negotiated at socket connect time and involves no protocol commands.) In short, sample code that can do https would be completely useless for comparing to TLS-enabled code. IMAP is somewhat harder than SMTP; I suggest you read up on the protocol. I've done a fair amount of work with it, and still would have to refer to the RFC to establish a connection without the help of an existing IMAP library. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What is a Haskell way to implement flags?
On Tue, Feb 19, 2013 at 10:11 AM, Branimir Maksimovic bm...@hotmail.comwrote: In C usual way is to set some bit in integer variable by shifting or oring, and than check flag integer variable by anding with particular flag value. What is Haskell way? You can do that, but a somewhat more idiomatic way would be a list (or, slightly less conveniently but more accurately, a Data.Set) of constructors from a flags ADT. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] performance question
On Tue, Feb 12, 2013 at 11:32 PM, bri...@aracnet.com wrote: actualy native code compiler. Can't regex be done effectively in haskell ? Is it something that can't be done, or is it just such minimal effort to link to pcre that it's not worth the trouble ? PCRE is pretty heavily optimized. POSIX regex engines generally rely on vendor regex libraries which my not be well optimized; there is a native Haskell implementation as well, but that one runs into a different issue, namely a lack of interest (regexes are often seen as foreign to Haskell-think, so there's little interest in making them work well; people who *do* need them for some reason usually punt to pcre). -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] performance question
On Wed, Feb 13, 2013 at 11:32 AM, Nicolas Bock nicolasb...@gmail.comwrote: Since I have very little experience with Haskell and am not used to Haskell-think yet, I don't quite understand your statement that regexes are seen as foreign to Haskell-think. Could you elaborate? What would a more native solution look like? From what I have learned so far, it seems to me that Haskell is a lot about clear, The native solution is a parser like parsec/attoparsec. The problem with regexes is that you can't at compile time verify that, for example, you have as many matching groups in the regex as the code using it expects, nor does an optional matching group behave as a Maybe like it should; nor are there nice ways to recover. A parser gives you full control and better compile time checking, and is generally recommended. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] performance question
On Wed, Feb 13, 2013 at 12:46 PM, David Thomas davidleotho...@gmail.comwrote: The fact that parsec and attoparsec exist and can be pressed into service with reasonable performance (I think?) on tasks for which regexps are suitable is probably another big part of the reason no one's done it yet. I expect much of the plumbing would wind up looking a lot like those, actually. When I started out with Haskell, one of my early thoughts was about designing a DSL for Icon-style pattern matching; I dropped it when I realized I was reinventing (almost identically, at least for its lower level combinators) Parsec. Nothing really to be gained except from a tutelary standpoint. And the mapping from Icon patterns to regex patterns is pretty much mechanical if you phrase it so you aren't executing code in the middle. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] performance question
On Wed, Feb 13, 2013 at 5:45 PM, o...@cs.otago.ac.nz wrote: On 13.02.2013 21:41, Brandon Allbery wrote: The native solution is a parser like parsec/attoparsec. Aleksey Khudyakov alexey.sklad...@gmail.com replied Regexps only have this problem if they are compiled from string. Nothing prevents from building them using combinators. regex-applicative[1] uses this approach and quite nice to use. [1] http://hackage.haskell.org/package/regex-applicative That _is_ a nice package, but it _is_ 'a parser like parsec/attoparsec'. Well, yes; it's a case in point. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How far compilers are allowed to go with optimizations?
On Sat, Feb 9, 2013 at 3:56 AM, Johan Holmquist holmi...@gmail.com wrote: The code goes into production and, disaster. The new improved version runs 3 times slower than the old, making it practically unusable. The new version has to be rolled back with loss of uptime and functionality and management is not happy with P. It just so happened that the old code triggered some aggressive optimization unbeknownst to everyone, **including the original developer**, while the new code did not. (This optimization maybe even This leads ultimately to not allowing compilers to optimize at all. I suspect that's a bad plan. Keep in mind that a modern web application may be heavily enough used that it doesn't even need to be a hyper-optimization; even small changes in performance can scale to large performance differences. Also... what happens when it's not just manual optimization but a bug fix that triggers this? Maybe this is something that would never happen in practice, but how to be sure... If this really scares you, disable all compiler optimization. Now you can be sure even at large scales where even small changes can have huge effects... and now you'd better be good at hand optimization. And writing code in assembly language so you can get that optimization. This sounds like going backwards to me. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How far compilers are allowed to go with optimizations?
On Wed, Feb 6, 2013 at 6:45 AM, Jan Stolarek jan.stola...@p.lodz.pl wrote: nevertheless I objected to his opinion, claiming that if compiler performed such a high-level optimization - replace underlying data structure with a different one and turn one algorithm into a completely different one - programmer wouldn't be able to reason about space behaviour of a program. I concluded that such a solution should not be built into a compiler but instead turned into an EDSL. For what it's worth, the main dividing line between -O1 and -O2 in gcc is that -O2 may change space or time behavior in unexpected ways. (This may explain e.g. https://plus.google.com/u/0/102208456519922110915/posts/DZsZ6mvA4T6) -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Next Meetup
On Mon, Feb 4, 2013 at 3:53 PM, Albert Y. C. Lai tre...@vex.net wrote: Toronto is an international metropolis with three globally renowned universities, multiple major-player high-tech labs, a world-class orchestra and several world-class choirs, and fine cuisines from almost all cultures. Toronto is home of the Toronto Haskell Meetup. The Toronto Haskell Meetup welcomes attendees from all over the world. I'm sure, but it still helps to say *which* meetup is inviting those attendees -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] linking errors while compile hugs98 in macos
On Thu, Jan 31, 2013 at 1:31 AM, Junior White efi...@gmail.com wrote: Hi Cafe, I downloaded the latest hugs98 source package, unzip and build, I get the following link errors. It seems many symbols are not defined, am I missing same depending libraries? I don't think anyone is maintaining hugs any more. Undefined symbols for architecture x86_64: _environ, referenced from: ___hscore_environ in ccuTP291.o (maybe you meant: ___hscore_environ) environ is a legacy pre-standards interface to the process environment and has been deprecated for a long time; it looks like Mountain Lion no longer exports it at all. More proof that hugs is moribund, if it's still using those ancient interfaces. -- brandon s allbery kf8nh sine nomine associates allber...@gmail.com ballb...@sinenomine.net unix, openafs, kerberos, infrastructure, xmonadhttp://sinenomine.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
