[Haskell-cafe] threadDelay
Am I correct in assuming this program should run 100 secs? import Control.Concurrent main = do threadDelay 10 Why do I get the folling result then? ghc -threaded Main.hs -o delay time ./delay real0m0.104s user0m0.001s sys0m0.002s Thanks in advance for all your wonderful comments, Immanuel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Comments from OCaml Hacker Brian Hurt
It's a criticism already voiced by the great David Bowie: My Brain Hurt like a warehouse, it had no room to spare I had to cram so many things to store everything in there Immanuel On Thu, Jan 15, 2009 at 4:34 PM, John Goerzen jgoer...@complete.org wrote: Hi folks, Don Stewart noticed this blog post on Haskell by Brian Hurt, an OCaml hacker: http://enfranchisedmind.com/blog/2009/01/15/random-thoughts-on-haskell/ It's a great post, and I encourage people to read it. I'd like to highlight one particular paragraph: One thing that does annoy me about Haskell- naming. Say you've noticed a common pattern, a lot of data structures are similar to the difference list I described above, in that they have an empty state and the ability to append things onto the end. Now, for various reasons, you want to give this pattern a name using on Haskell's tools for expressing common idioms as general patterns (type classes, in this case). What name do you give it? I'd be inclined to call it something like Appendable. But no, Haskell calls this pattern a Monoid. Yep, that's all a monoid is- something with an empty state and the ability to append things to the end. Well, it's a little more general than that, but not much. Simon Peyton Jones once commented that the biggest mistake Haskell made was to call them monads instead of warm, fluffy things. Well, Haskell is exacerbating that mistake. Haskell developers, stop letting the category theorists name things. Please. I beg of you. I'd like to echo that sentiment! He went on to add: If you?re not a category theorists, and you're learning (or thinking of learning) Haskell, don't get scared off by names like monoid or functor. And ignore anyone who starts their explanation with references to category theory- you don't need to know category theory, and I don't think it helps. I'd echo that one too. -- John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] some ideas for Haskell', from Python
2) In Python it is possible to import modules inside a function. In Haskell something like: joinPath' root name = joinPath [root, name] importing System.FilePath (joinPath) In Python importing a module has totally different semantics from importing in Haskell. I runs the initialization code for the module makes the names in that module available to you code. In Haskell modules are just namespace control, and you can always refer to names imported through import X through the syntax X.name. This means that the local import in Python solves two problems 1) making a name available locally. 2) running initialization code only when a specific function is called. Neither of those makes any sense for Haskell as far as I can tell. Immanuel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Taking Exception to Exceptions
I recommend this paper for info, it's very easy to follow: http://www.haskell.org/~simonmar/papers/ext-exceptions.pdfhttp://www.haskell.org/%7Esimonmar/papers/ext-exceptions.pdf Austin That paper cleared up most of my issues and it is amazing that it is not amongst the papers that are referenced at the top of the the page describing Control.Exception. Anyway, there is one more problem I have related to exceptions that is about forcing strictness. It relates to option parsing. I have an option -t that says which track from a file of tracks to print. So I go data Flags = TrackNumber !Int deriving(Read, Show, Eq) makeTrackNumber :: String - Flags makeTrackNumber str = TrackNumber $ read str options = [GetOpt.Option ['t'] [tracknumber] (GetOpt.ReqArg makeTrackNumber tracknumber) number of track to show] Now my main goes main = do args - getArgs opts - evaluate $ GetOpt.getOpt GetOpt.RequireOrder options args print done getting the opts case opts of ... which of course first prints done getting opts and then throws an exception if I give it a flag -t abc. What would be the way to proceed here? Do I increase the strictness or do I write a handler around my complete main? Even if I map the exception in makeTrackNumber to my very own exception how do I find out which exact call gave a problem i.e. which is the call stack at the moment the exception was thrown -- I might use makeTrackNumber in other contexts too. Thanks in advance, Immanuel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Taking Exception to Exceptions
I'm trying to use the new (for me at least) extensible exceptions and I am little amazed that I cannot get catch, try or mapException to work without telling them which exceptions I want to catch. What is the rationale behind this? How does bracket manage to catch all exceptions? What should onException do? Is there some example code that uses these exceptions, or better documentation? Thanks in advance, Immanuel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Why Not Haskell?
Reilly Hayes [EMAIL PROTECTED] writes: On Aug 8, 2006, at 1:42 AM, Immanuel Litzroth wrote: Reilly Hayes [EMAIL PROTECTED] writes: I don't understand your argument. How exactly does the GPL get in the way of selling software as an instantiation of business expertise? Are you saying that you have the business expertise but customers still prefer not to buy your software? Doesn't that just mean that your expertise isn't worth much (economic evaluation :-). Or that your idea that they were buying expertise was not correct, they were just buying the software after all, and now they have an alternative? I failed to communicate my case clearly. The software *is* what is being sold. The *reason* it is valuable is the business expertise required to build it. There are markets with very small populations of people who both understand the business thoroughly and can implement solutions. It makes software valuable and makes licensing the most effective way to monetize that value. I am not arguing that licensing would not be a very effective way to monetize value. Yes I know the business model. Sell them some overpriced software charge them through the nose for support, features, training, installation, updates Your resentment against the GPL stems from the fact that it makes squeezing the last buck out of your clients somewhat harder (in some markets). It probably annoys you that you are not dealing with a competitor who is making shitloads of money, making some price fixing or secret agreements not feasable. Your problem is that just as your business practice is not illegal, neither is the GPL. This paragraph is way out of line. You have taken a discussion of the merits of using GPL software and turned it into a personal attack. Attack the argument, not the arguer. It would be both polite and reasonable to tone down the hostility if you actually want a discussion. Yeah, it might have been harsh and I apologize. But I just describe what I have seen in some of the companies I worked for. I don't have a problem with the GPL. In my professional life, I am careful to avoid GPL software in those cases where the GPL would interfere with the firm's commercial interests. I certainly don't resent the GPL or those who choose to release software under the GPL. In fact, I can imagine wanting to release some kinds of software under the GPL. The point I was making was that the GPL *does* get in the way of *some* optimal mechanisms of making money. Which is *fine*. That is one of the *intents* of the GPL. The argument that I am trying to counter is the one that says open source is *always* better for everybody. I don't think the *intent* of the GPL is to get in the way of some optimal ways of making money. Can you tell me which part of the GPL makes you think? It might have that side-effect though. Sometimes, the best thing for the owner of the intellectual property is to keep it closed. There *are* markets where monetization of IP is a zero sum game, or worse (if the IP is public, nobody makes any money). I wonder who you see as the participants in this game? A worse than zero sum game might be interesting if you are one of the people who score positive and some of the other people have to pay for it. Gambling is a fine example. I'm not making (or getting involved in) the moral argument about free or open software. I will point out that the current good health of Haskell owes a great deal to Microsoft through the computer scientists they employ. I'm sure Haskell has benefitted from the largesse of other companies as well. That is definitely wrong. Haskell would be in even greater shape if some people who shall remain unnamed had not gone over to Microsoft. I foresee an interesting discussion here. I don't see how you can say Haskell would be better OR worse off if people hadn't gone to work for Microsoft. It's an entirely hypothetical case and it's just not knowable. My point is much simpler. Haskell GHC do benefit from the efforts of people being paid by Microsoft. Microsoft is planning to hire a full-time contractor to work on GHC. It seems irony gets lost so easily in these conversations. You have no way of knowing what the state of haskell would have been had certain key contributors to GHC and Haskell not taken jobs at Microsoft. Therefore you statement is meaningless and only good for producing approving nods among people who already agree with what you say. The snarky comment about people who shall remain unnamed is rude. I did not mean to be rude, and would like to apologize if anyone felt personally attacked by this. Immanuel -- *** I can, I can't. Tubbs Tattsyrup -- Immanuel
Re: [Haskell-cafe] Re: Why Not Haskell?
Reilly Hayes [EMAIL PROTECTED] writes: On Aug 7, 2006, at 10:00 AM, Stefan Monnier wrote: In any case, making a living by selling a program (as opposed to services around that program) is a difficult business. Making a living writing and selling programs for use by a wide audience is one thing. But there is a lot of money to be made by developers who really understand a complex niche market (assuming the niche is actually populated by customers who need and can pay for the product). And the GPL absolutely gets in the way of that. Because what you're really selling in that kind of market is software as an instantiation of business expertise. I don't understand your argument. How exactly does the GPL get in the way of selling software as an instantiation of business expertise? Are you saying that you have the business expertise but customers still prefer not to buy your software? Doesn't that just mean that your expertise isn't worth much (economic evaluation :-). Or that your idea that they were buying expertise was not correct, they were just buying the software after all, and now they have an alternative? Maybe you should thank the FSF for making you doubt: you should really think very hard about how you're going to make a living off of selling a program, even if that program hasn't been anywhere near any GPL'd code. In all likelihood it'll be much easier to earn your money by selling services around your program than just the program itself. Selling services is much easier if you can tie the services to IP that you own exclusively. It can also double your firm's daily rate on related services. And the economics of selling product (the program) can be MUCH better, assuming people want to use the program. If they don't, then you don't have a service business either. Yes I know the business model. Sell them some overpriced software charge them through the nose for support, features, training, installation, updates Your resentment against the GPL stems from the fact that it makes squeezing the last buck out of your clients somewhat harder (in some markets). It probably annoys you that you are not dealing with a competitor who is making shitloads of money, making some price fixing or secret agreements not feasable. Your problem is that just as your business practice is not illegal, neither is the GPL. I'm not making (or getting involved in) the moral argument about free or open software. I will point out that the current good health of Haskell owes a great deal to Microsoft through the computer scientists they employ. I'm sure Haskell has benefitted from the largesse of other companies as well. That is definitely wrong. Haskell would be in even greater shape if some people who shall remain unnamed had not gone over to Microsoft. I foresee an interesting discussion here. Immanuel -- *** I can, I can't. Tubbs Tattsyrup -- Immanuel Litzroth Software Development Engineer Enfocus Software Antwerpsesteenweg 41-45 9000 Gent Belgium Voice: +32 9 269 23 90 Fax : +32 9 269 16 91 Email: [EMAIL PROTECTED] web : www.enfocus.be *** ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why Not Haskell?
Brian Hulley [EMAIL PROTECTED] writes: I meant even a non-programmer in the sense of even someone who is not a C hacker to show that the threat of people being able to steal code from a program is not the only source of problems that GPL could impose on a commercial application. No derogatory implication towards people who choose not to learn computer programming was intended. The GPL itself refers to a cost of distribution, since it recognizes such things are not free-in-price. This is in reference to offering a copy of the source code. The price of a binary copy can be as large as desired. Likewise for the cost of support. Well I understand the free as in free speech not free beer motto, but suppose person A is talented at writing software but prefers a peaceful existence and lacks the contacts/refs/desire/energy etc to be a consultant or contractor, and has had the bad experience of being forced to work extremely long hours with low pay while in an employed position, and person B is outgoing, ebullient, and talented at marketing and advertising. Now person A spends some years quietly writing some code, which uses a GPL library and is therefore GPL'd, and sells it, as is his/her right under the GPL to person B. Then person B is free, as in free speech to do whatever he/she likes with the software, and so in particular could use his/her marketing skills to completely undermine person A's one and only hope of earning a living, so from person A's point of view the *amortized* effect of the GPL is to make his/her software free as in free beer as well. Then someone discovers a bug in the program of person A. Person B is being so busy being outgoing, ebullient and effervescent that he does not easily find the cause of the bug. Moreover the code needs to be ported to a the new Warthog MacOSX release. Person A being not only talented but also shrewd now uses the contractual obligations of person B as leverage to screw him out of most of his previously made profit for delivering said work. He lived peacefully ever after. What is this, Economic Analysis by Parable? Immanuel -- *** I can, I can't. Tubbs Tattsyrup -- Immanuel Litzroth Software Development Engineer Enfocus Software Antwerpsesteenweg 41-45 9000 Gent Belgium Voice: +32 9 269 23 90 Fax : +32 9 269 16 91 Email: [EMAIL PROTECTED] web : www.enfocus.be *** ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] if-then-else as rebindable syntax
Doaitse Swierstra [EMAIL PROTECTED] writes: We alreday are at a stage where first year students trying to master haskell get error messages like Bool is not an instance of the class Num if they accidently write 1 + True (or something equivalent, but less obvious). Good! It will prepare them for C++ error messages of several pages because you forgot to write const next to a member function, thus make the transition from Haskell to something that pays the rent easier. In short: you will not make Haskell a lot more popular by attracting category theorists, but by making transitions from Java and C as smooth and surprise-free as possible (and this is already hard enough). Are we talking about the straw that broke the camel's back? Are you serious about making Java/C programmers transition to Haskell? What would be the purpose of that? Immanuel -- *** I can, I can't. Tubbs Tattsyrup -- Immanuel Litzroth Software Development Engineer Enfocus Software Antwerpsesteenweg 41-45 9000 Gent Belgium Voice: +32 9 269 23 90 Fax : +32 9 269 16 91 Email: [EMAIL PROTECTED] web : www.enfocus.be *** ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language shootout (reloaded)
Stefan Holdermans [EMAIL PROTECTED] writes: Still---and, please, forgive me for this---I feel that us being #1 now tells us more about the Haskell community than it tells us about Haskell. How to optimize Haskell code: 1) enter it as a test in the great language shootout. 2) wait a few days. 3) download optimized code. Immanuel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Haskell versus Lisp
David F. Place [EMAIL PROTECTED] writes: I was hoping that the examples I requested would be examples of particular control constructs or extensions to the language's syntax and semantics. Though I admit that such things are possible in lisp, I suspect that their utility is minimal. Ever heard of the loop macro? Immanuel Litzroth ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Haskell versus Lisp
Tomasz Zielonka [EMAIL PROTECTED] writes: On Wed, Sep 21, 2005 at 08:53:47AM +0100, Immanuel Litzroth wrote: David F. Place [EMAIL PROTECTED] writes: I was hoping that the examples I requested would be examples of particular control constructs or extensions to the language's syntax and semantics. Though I admit that such things are possible in lisp, I suspect that their utility is minimal. Ever heard of the loop macro? Immanuel Litzroth I would be nice if you could give some examples for use of LOOP macro that you think would be cumbersome to translate to Haskell. That was not the original question and I think that would lead to pointless discussion about the meaning of cumbersome. Loop is an example of a control construct that can be implemented by a macro. One can can discuss it's utility, but it was deemed important enough to be standardized (by lisp people). It was only one of the macros developed at that time to do things sequencelike things (series, generators/gatherers were others) . Another example is UFFI, basically a bunch of macros to do platform independent foreign function interfaces. I a currently writing a macro to generate the functions and datastructures to read an ipod database. This allows me to declaratively say (defheader (header-name inherits-from) (field-name length optional reader)...). I doubt this would be easy in Haskell (maybe with TH it could be done) since I build a list of (header-name . (field-names ...)) at compile time which is then used to generate code that locally binds these to the result of reading them so that readers can refer to fields already read e.g. (let* ((field-name (reader stream))) ((field-name2 (reader field-name1 stream)) Immanuel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Haskell versus Lisp
David F. Place [EMAIL PROTECTED] writes: On Sep 21, 2005, at 3:53 AM, Immanuel Litzroth wrote: Ever heard of the loop macro? Yes, the loop macro is a good example for the argument against lisp. Lisp has features to support iteration that date back to the time before it was understood that tail recursion is equivalent to iteration. In fact, even in the early '90s most common lisp compilers didn't implement tail-merging. I doubt there is any program implemented using the loop macro that couldn't be more elegantly implemented recursively. In fact, when writing in lisp or scheme, I always write recursively now that I can depend on compilers to tail- merge. I personally find loop usually the most concise way to express my iteration requirements. Immanuel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
