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• "Work stealing" vs. "Work shrugging"?

  - by John

  Why is it that I can find lots of information on "work stealing" and nothing on "work shrugging" as a dynamic load-balancing strategy? By "work-shrugging" I mean busy processors pushing excessive work towards less loaded neighbours rather than idle processors pulling work from busy neighbours ("work-stealing"). I think the general scalability should be the same for both strategies. However I believe that it is much more efficient for busy processors to wake idle processors if and when there is definitely work for them to do than having idle processors spinning or waking periodically to speculatively poll all neighbours for possible work. Anyway a quick google didn't show up anything under the heading of "Work Shrugging" or similar so any pointers to prior-art and the jargon for this strategy would be welcome. Clarification/Confession In more detail:- By "Work Shrugging" I actually envisage the work submitting processor (which may or may not be the target processor) being responsible for looking around the immediate locality of the preferred target processor (based on data/code locality) to decide if a near neighbour should be given the new work instead because they don't have as much work to do. I am talking about an atomic read of the immediate (typically 2 to 4) neighbours' estimated q length here. I do not think this is any more coupling than implied by the thieves polling & stealing from their neighbours - just much less often - or rather - only when it makes economic sense to do so. (I am assuming "lock-free, almost wait-free" queue structures in both strategies). Thanks.

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• Test Views in ASP.NET MVC2 (ala RSpec)

  - by Dmitriy Nagirnyak

  Hi, I am really missing heavily the ability to test Views independently of controllers. The way RSpec does it. What I want to do is to perform assertions on the rendered view (where no controller is involved!). In order to do so I should provide required Model, ViewData and maybe some details from HttpContextBase (when will we get rid of HttpContext!). So far I have not found anything that allows doing it. Also it might heavily depend on the ViewEngine being used. List of things that views might contain are: Partial views (may be nested deeply). Master pages (or similar in other view engines). Html helpers generating links and other elements. Generally almost anything in a range of common sense :) . Also please note that I am not talking about client-side testing and thus Selenium is just not related to it at all. It is just plain .NET testing. So are there any options to actually do the testing of views? Thanks, Dmitriy.

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• Capturing time intervals when somebody was online? How would you impement this feature?

  - by Kirzilla

  Hello, Our aim is to build timelines saying about periods of time when user was online. (It really doesn't matter what user we are talking about and where he was online) To get information about onliners we can call API method, someservice.com/api/?call=whoIsOnline whoIsOnline method will give us a list of users currently online. But there is no API method to get information about who IS NOT online. So, we should build our timelines using information we got from whoIsOnline. Of course there will be a measurement error (we can't track information in realtime). Let's suppose that we will call whoIsOnline method every 2 minutes (yes, we will run our script by cron every 2 minutes). For example, calling whoIsOnline at 08:00 will return Peter_id Michal_id Andy_id calling whoIsOnline at 08:02 will return Michael_id Andy_id George_id As you can see, Peter has gone offline, but we have new onliner - George. Available instruments are Db(MySQL) / text files / key-value storage (Redis/memcache); feel free to choose any of them (or even all of them). So, we have to get information like this George_id was online... 12 May: 08:02-08:30, 12:40-12:46, 20:14-22:36 11 May: 09:10-12:30, 21:45-23:00 10 May: was not online And now question... How would you store information to implement such timelines? How would you query/calculate information about periods of time when user was online? Additional information.. You cannot update information about offline users, only users who are "currently" online. Solution should be flexible: timeline information could be represented relating to any timezone. We should keep information only for last 7 days. Every user seen online is automatically getting his own identifier in our database. Uff.. it was really hard for me to write it because my English is pretty bad, but I hope my question will be clear for you. Thank you.

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• why unsigned int 0xFFFFFFFF is equal to int -1?

  - by conejoroy

  perhaps it's a very stupid question but I'm having a hard time figuring this out =) in C or C++ it is said that the maximum number a size_t (an unsigned int data type) can hold is the same as casting -1 to that data type. for example see http://stackoverflow.com/questions/1420982/invalid-value-for-sizet Why?? I'm confused.. I mean, (talking about 32 bit ints) AFAIK the most significant bit holds the sign in a signed data type (that is, bit 0x80000000 to form a negative number). then, 1 is 0x00000001.. 0x7FFFFFFFF is the greatest positive number a int data type can hold. then, AFAIK the binary representation of -1 int should be 0x80000001 (perhaps I'm wrong). why/how this binary value is converted to anything completely different (0xFFFFFFFF) when casting ints to unsigned?? or.. how is it possible to form a binary -1 out of 0xFFFFFFFF? I have no doubt that in C: ((unsigned int)-1) == 0xFFFFFFFF or ((int)0xFFFFFFFF) == -1 is equally true than 1 + 1 == 2, I'm just wondering why. thanks!

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• How can I use "Dependency Injection" in simple php functions, and should I bother?

  - by Tchalvak

  I hear people talking about dependency injection and the benefit of it all the time, but I don't really understand it. I'm wondering if it's a solution to the "I pass database connections as arguments all the time" problem. I tried reading wikipedia's entry on it, but the example is written in Java so I don't solidly understand the difference it is trying to make clear. ( http://en.wikipedia.org/wiki/Dependency_injection ). I read this dependency-injection-in-php article ( http://www.potstuck.com/2009/01/08/php-dependency-injection/ ), and it seems like the objective is to not pass dependencies to an object directly, but to cordon off the creation of an object along with the creation of it's dependencies. I'm not sure how to apply that in a using php functions context, though. Additionally, is the following Dependency Injection, and should I bother trying to do dependency injection in a functional context? Version 1: (the kind of code that I create, but don't like, every day) function get_data_from_database($database_connection){ $data = $database_connection->query('blah'); return $data; } Version 2: (don't have to pass a database connection, but perhaps not dependency injection?) function get_database_connection(){ static $db_connection; if($db_connection){ return $db_connection; } else { // create db_connection ... } } function get_data_from_database(){ $conn = get_database_connection(); $data = $conn->query('blah'); return $data; } $data = get_data_from_database(); Version 3: (the creation of the "object"/data is separate, and the database code is still, so perhaps this would count as dependency injection?) function factory_of_data_set(){ static $db_connection; $data_set = null; $db_connection = get_database_connection(); $data_set = $db_connection->query('blah'); return $data_set; } $data = factory_of_data_set(); Anyone have a good resource or just insight that makes the method and benefit -crystal- clear?

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• Copying a directory that is version controlled

  - by ibz

  I am curious whether it is OK to copy a directory that is under version control and start working on both copies. I know it can be different from one VCS to another, but I intentionally don't specify any VCS since I am curious about different cases. I was talking to a coworker recently about doing it in SVN. I think it should be OK, but I am still not 100% sure, since I don't know what exactly SVN is storing in the working copy. However, if we talk about the DVCS world, things might be even more unclear, since every working copy is a repository by itself. Being faced with doing this in bzr now, I decided to ask the question. Later edit: Some people asked why I would want to do that. Here is the whole story: In the case of SVN it was because being out of the office, the connection to the SVN server was really slow, so me and my coworker decided to check out the sources only once and make a local copy. That's what we did and it worked OK, but I am still wondering whether it is guaranteed to work, or it just happened. In the bzr case, I am planning to move the "main" repo to another server. So I was thinking to just copy it there and start considering that the main repo. I guess the safest is to make a clone though.

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• Why is cell phone software is still so primitive?

  - by Tomislav Nakic-Alfirevic

  I don't do mobile development, but it strikes me as odd that features like this aren't available by default on most phones: full text search: searches all address book contents, messages, anything else being a plus better call management: e.g. a rotating audio call log, meaning you always have the last N calls recorded for your listening pleasure later (your little girl just said her first "da-da" while you were on a business trip, you had a telephone job interview, you received complex instructions to do something etc.) bluetooth remote control (like e.g. anyRemote, but available by default on a bluetooth phone) no multitasking capabilities worth mentioning and in general no e.g. weekly software updates, making the phone much more usable (even if it had to be done over USB, rather than over the network). I'm sure I was dumbfounded by the lack or design of other features as well, but they don't come to mind right now. To clarify, I'm not talking about smartphones here: my plain, 2-year old phone has a CPU an order of magnitude faster than my first PC, about as much storage space and it's ridiculous how bad (slow, unwieldy) the software is and it's not one phone or one manufacturer. What keeps the (to me) obvious software functionality vacuum on a capable hardware platform from being filled up?

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• iPhone OS: Strategies for high density image work

  - by Jasconius

  I have a project that is coming around the bend this summer that is going to involve, potentially, an extremely high volume of image data for display. We are talking hundreds of 640x480-ish images in a given application session (scaled to a smaller resolution when displayed), and handfuls of very large (1280x1024 or higher) images at a time. I've already done some preliminary work and I've found that the typical 640x480ish image is just a shade under 1MB in memory when placed into a UIImageView and displayed... but the very large images can be a whopping 5+ MB's in some cases. This project is actually be targeted at the iPad, which, in my Instruments tests seems to cap out at about 80-100MB's of addressable physical memory. Details aside, I need to start thinking of how to move huge volumes of image data between virtual and physical memory while preserving the fluidity and responsiveness of the application, which will be high visibility. I'm probably on the higher ends of intermediate at Objective-C... so I am looking for some solid articles and advice on the following: 1) Responsible management of UIImage and UIImageView in the name of conserving physical RAM 2) Merits of using CGImage over UIImage, particularly for the huge images, and if there will be any performance gain 3) Anything dealing with memory paging particularly as it pertains to images I will epilogue by saying that the numbers I have above maybe off by about 10 or 15%. Images may or may not end up being bundled into the actual app itself as opposed to being loaded in from an external server.

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• Are short tags *that* bad?

  - by Col. Shrapnel

  Everyone here on SO says it's bad, for 3 main reasons: XML is used everywhere You can't control where your script is going to be run short tags are going to be removed in PHP6 But let's see closer at them: Last one is easy - it's just not true. XML is not really a problem. If you want to use short tags, it won't be a problem for you to write a single tag using PHP echo, <?="<?XML...?>"?>. Anyway, why not to leave such a trifle thing for one's own judgment? PHP configuration access. Oh yes, the only thing that can be really considered as a reason. Of course in case you plan to spread your code wide. But if you don't? I think most of scripts being written not for the wide spread, but just for one place. If you can use short tags in that place - why to abandon them? Anyway, it's the only template we are talking about. If you don't like short tags, PHP native template is probably not for you, why not to try Smarty then? Well, the question is: is there any other real reasons to abandon short tags and make it strict recommendation? Or, as it was said, better to leave short tags alone?

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• Good mobile oriented GWT widget library alternatives

  - by Michael Donohue

  I've been developing a travel planning site - tripgrep.com - which is built on appengine, GWT and smartgwt, among other technologies. It is still early days, and the site is now working well on my development environment, which is either a windows or mac computer. However, I am frequently talking up the website to my friends when we are at a bar or other venue, so I am standing there while they try to access the site via an iPhone, Android or Blackberry - I've witnessed all three. It has been painfully obvious that the browser based frontend takes a long time to download on a mobile device. I am pretty sure this is because of the javascript download for SmartGWT. So, I would like to look at alternatives to SmartGWT. What I like about SmartGWT is that it has a reasonable look and feel out of the box - I don't need to learn any design or css and it has an office application look. This is considerably better than the GWT built-in widgets, which just get a blue border. The better look-and-feel is why I went with SmartGWT early on. However, the slow load times are killing me on these mobile demos. So now I want a fast loading widget alternative that has good look-and-feel out of the box. The features I care about are: tabs, good form layout, Google maps API integration, grid data viewing. If those are all available in a library that loads quickly on a mobile device, then that's the library I want.

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• How can I get bitfields to arrange my bits in the right order?

  - by Jim Hunziker

  To begin with, the application in question is always going to be on the same processor, and the compiler is always gcc, so I'm not concerned about bitfields not being portable. gcc lays out bitfields such that the first listed field corresponds to least significant bit of a byte. So the following structure, with a=0, b=1, c=1, d=1, you get a byte of value e0. struct Bits { unsigned int a:5; unsigned int b:1; unsigned int c:1; unsigned int d:1; } __attribute__((__packed__)); (Actually, this is C++, so I'm talking about g++.) Now let's say I'd like a to be a six bit integer. Now, I can see why this won't work, but I coded the following structure: struct Bits2 { unsigned int a:6; unsigned int b:1; unsigned int c:1; unsigned int d:1; } __attribute__((__packed__)); Setting b, c, and d to 1, and a to 0 results in the following two bytes: c0 01 This isn't what I wanted. I was hoping to see this: e0 00 Is there any way to specify a structure that has three bits in the most significant bits of the first byte and six bits spanning the five least significant bits of the first byte and the most significant bit of the second? Please be aware that I have no control over where these bits are supposed to be laid out: it's a layout of bits that are defined by someone else's interface.

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• Calling a method on an unitialized object (null pointer)

  - by Florin

  What is the normal behavior in Objective-C if you call a method on an object (pointer) that is nil (maybe because someone forgot to initialize it)? Shouldn't it generate some kind of an error (segmentation fault, null pointer exception...)? If this is normal behavior, is there a way of changing this behavior (by configuring the compiler) so that the program raises some kind of error / exception at runtime? To make it more clear what I am talking about, here's an example. Having this class: @interface Person : NSObject { NSString *name; } @property (nonatomic, retain) NSString *name; - (void)sayHi; @end with this implementation: @implementation Person @synthesize name; - (void)dealloc { [name release]; [super dealloc]; } - (void)sayHi { NSLog(@"Hello"); NSLog(@"My name is %@.", name); } @end Somewhere in the program I do this: Person *person = nil; //person = [[Person alloc] init]; // let's say I comment this line person.name = @"Mike"; // shouldn't I get an error here? [person sayHi]; // and here [person release]; // and here

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• Hotkeys in webapps

  - by Johoo

  When creating webapps, is there any guidelines on which keys you can use for your own hotkeys without overriding too many of the browsers default hotkeys. For example i might want to have a custom copy command for copying entire sets of data that only makes sense for my program instead of just text. The logical combination for this would be ctrl+c but that would destroy the default copy hotkey for normal text. One solution i was thinking about is to only catch the hotkey when it "makes sense" but when you use some advanced custom selection it might be hard to differentiate if your data is focused, if text is selected or both. Right now i am only using single keys as the hotkey, so just 'c' for the example above and this seems to be what most other sites are doing too. The problem is that if you have text input this doesn't work so good. Is this the best solution? To clarify I'm talking about advanced webapps that behave more like normal programs and not just some website presenting information(even though i think these guidlines would be valid for both cases). So for the copy example it might not be a big deal if you can't copy the text in the menu but when ctrl+tab, alt+d or ctrl+e doesn't work i would be really pissed, cough flash cough.

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• NHibernate IQueryable Collection as Property of Root

  - by Khalid Abuhakmeh

  Hello and thank you for taking the time to read this. I have a root object that has a property that is a collection. For example : I have a Shelf object that has Books. // now public class Shelf { public ICollection<Book> Books {get; set;} } // want public class Shelf { public IQueryable<Book> Books {get;set;} } What I want to accomplish is to return a collection that is IQueryable so that I can run paging and filtering off of the collection directly from the the parent. var shelf = shelfRepository.Get(1); var filtered = from book in shelf.Books where book.Name == "The Great Gatsby" select book; I want to have that query executed specifically by NHibernate and not a get all to load a whole collection and then parse it in memory (which is what currently happens when I use ICollection). The reasoning behind this is that my collection could be huge, tens of thousands of records, and a get all query could bash my database. I would like to do this implicitly so that when NHibernate sees and IQueryable on my class it knows what to do. I have looked at NHibernates Linq provider and currently I am making the decision to take large collections and split them into their own repository so that I can make explicit calls for filtering and paging. Linq To SQL offers something similar to what I'm talking about.

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• Ignore LD_LIBRARY_PATH and stick with library given through -rpath at link time

  - by roe

  I'm sitting in an environment which I have no real control over (it's not just me, so basically, I can't change the environment or it won't work for anyone else), the only thing I can affect is how the binary is built. My problem is, the environment specifies an LD_LIBRARY_PATH containing a libstdc++ which is not compatible with the compiler being used. I tried compiling it statically, but that doesn't seem possible for g++ (version 4.2.3, seems to have been work done in this direction in later versions though which are not available, -static-libstdc++ or something like that). Now I've arrived at using rpath to bake the absolute path name into the executable (would work, all machines it's supposed to run on are identical). Unfortunately it appears as though LD_LIBRARY_PATH takes precedence over rpath (resetting LD_LIBRARY_PATH confirmed that it's able to find the library, but as stated above, LD_LIBRARY_PATH will be set for everyone, and I cannot change that). Is there any way I can make rpath take precedence over LD_LIBRARY_PATH, or are there any other possible solutions to my problem? Note that I'm talking about dynamic linking at runtime, I am able to control the command line at compile and link time. Thanks.

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• What does flushing thread local memory to global memory mean?

  - by Jack Griffith

  Hi, I am aware that the purpose of volatile variables in Java is that writes to such variables are immediately visible to other threads. I am also aware that one of the effects of a synchronized block is to flush thread-local memory to global memory. I have never fully understood the references to 'thread-local' memory in this context. I understand that data which only exists on the stack is thread-local, but when talking about objects on the heap my understanding becomes hazy. I was hoping that to get comments on the following points: When executing on a machine with multiple processors, does flushing thread-local memory simply refer to the flushing of the CPU cache into RAM? When executing on a uniprocessor machine, does this mean anything at all? If it is possible for the heap to have the same variable at two different memory locations (each accessed by a different thread), under what circumstances would this arise? What implications does this have to garbage collection? How aggressively do VMs do this kind of thing? Overall, I think am trying to understand whether thread-local means memory that is physically accessible by only one CPU or if there is logical thread-local heap partitioning done by the VM? Any links to presentations or documentation would be immensely helpful. I have spent time researching this, and although I have found lots of nice literature, I haven't been able to satisfy my curiosity regarding the different situations & definitions of thread-local memory. Thanks very much.

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• Automatic .NET code, nhibernate session, and LINQ datacontext clean-up?

  - by AverageJoe719

  Hi all, in my goal to adopt better coding practices I have a few questions in general about automatic handling of code. I have heard different answers both from online and talking with other developers/programmers at my work. I am not sure if I should have split them into 3 questions, but they all seem sort of related: 1) How does .NET handle instances of classes and other code things that take up memory? I recently found out about using the factory pattern for certain things like service classes so that they are only instantiated once in the entire application, but then I was told that '.NET handles a lot of that stuff automatically when mentioning it.' 2) How does Nhibernate's session handle automatic clean-up of un-used things? I've seen some say that it is great at handling things automatically and you should just use a session factory and that's it, no need to close it. But I have also read and seem many examples where people close the hibernate session. 3) How does LINQ's datacontext handle this? Most of the time I never .disposed my datacontext's and the app didn't see to take a performance hit (though I am not running anything super intensively), but it seems like most people recommend disposing of your datacontext after you are done with it. However, I have seen many many code examples where the dispose method is never called. Also in general I found it kind of annoying that you couldn't access even one-deep child related objects after disposing of the datacontext unless you explicity also grabbed them in the query. Thanks all. I am loving this site so far, I kind of get lost and spend hours just reading things on here. =)

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• Multi-level shop, xml or sql. best practice?

  - by danrichardson

  Hello, i have a general "best practice" question regarding building a multi-level shop, which i hope doesn't get marked down/deleted as i personally think it's quite a good "subjective" question. I am a developer in charge (in most part) of maintaining and evolving a cms system and associated front-end functionality. Over the past half year i have developed a multiple level shop system so that an infinite level of categories may exist down into a product level and all works fine. However over the last week or so i have questioned by own methods in front-end development and the best way to show the multi-level data structure. I currently use a sql server database (2000) and pull out all the shop levels and then process them into an enumerable typed list with child enumerable typed lists, so that all levels are sorted. This in my head seems quite process heavy, but we're not talking about thousands of rows, generally only 1-500 rows maybe. I have been toying with the idea recently of storing the structure in an XML document (as well as the database) and then sending last modified headers when serving/requesting the document for, which would then be processed as/when nessecary with an xsl(t) document - which would be processed server side. This is quite a handy, reusable method of storing the data but does it have more overheads in the fact im opening and closing files? And also the xml will require a bit of processing to pull out blocks of xml if for instance i wanted to show two level mid way through the tree for a side menu. I use the above method for sitemap purposes so there is currently already code i have built which does what i require, but unsure what the best process is to go about. Maybe a hybrid method which pulls out the data, sorts it and then makes an xml document/stream (XDocument/XmlDocument) for xsl processing is a good way? - This is the way i currently make the cms work for the shop. So really (and thanks for sticking with me on this), i am just wandering which methods other people use or recommend as being the best/most logical way of doing things. Thanks Dan

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• Is the Windows dev environment worth the cost?

  - by MCS

  I recently made the move from Linux development to Windows development. And as much of a Linux enthusiast that I am, I have to say - C# is a beautiful language, Visual Studio is terrific, and now that I've bought myself a trackball my wrist has stopped hurting from using the mouse so much. But there's one thing I can't get past: the cost. Windows 7, Visual Studio, SQL Server, Expression Blend, ViEmu, Telerik, MSDN - we're talking thousands for each developer on the project! You're definitely getting something for your money - my question is, is it worth it? [Not every developer needs all the aforementioned tools - but have you ever heard of anyone writing C# code without Visual Studio? I've worked on pretty large software projects in Linux without having to pay for any development tool whatsoever.] Now obviously, if you're already a Windows shop, it doesn't pay to retrain all your developers. And if you're looking to develop a Windows desktop app, you just can't do that in Linux. But if you were starting a new web application project and could hire developers who are experts in whatever languages you want, would you still choose Windows as your development platform despite the high cost? And if yes, why?

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• A way to specify a different host in an SSH tunnel from the host in use

  - by Tom

  I am trying to setup an SSH tunnel to access Beanstalk (to bypass an annoying proxy server). I can get this to work, but with one caveat: I have to map my Beanstalk host URL (username.svn.beanstalkapp.com) in my hosts file to 127.0.0.1 (and use the ip in place of the domain when setting up the tunnel). The reason (I think) is that I am creating the tunnel using the local SSH instance (on Snow Leopard) and if I use localhost or 127.0.0.1 when talking to Beanstalk, it rejects the authorisation credentials. I believe this is because Beanstalk use the hostname specified in a request to determine which account the username / password combination should be checked against. If localhost is used, I think this information is missing (in some manner which Beanstalk requires) from the requests. At the moment I dig the IP for username.svn.beanstalkapp.com, map username.svn.beanstalkapp.com to 127.0.0.1 in my hosts file, then for the tunnel I use the command: ssh -L 8080:ip:443 -p 22 -l tom -N 127.0.0.1 I can tell Subversion that the repo. is located at: https://username.svn.beanstalkapp.com:8080/repo-name This uses my tunnel and the username and password are accepted. So, my question is if there is an option when setting up the SSH tunnel which would mean I wouldn't have to use my hosts file workaround?

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• How do programming languages bind identifiers to functions

  - by sub

  I'm talking about C and/or C++ here as this are the only languages I know used for interpreters where the following could be a problem: If we have an interpreted language X how can a library written for it add functions to the language which can then be called from within programs written in the language? PHP example: substr( $str, 5, 10 ); How is the function substr added to the "function pool" of PHP so it can be called from within scripts? It is easy for PHP storing all registered function names in an array and searching through it as a function is called in a script. However, as there obviously is no eval in C(++), how can the function then be called? I assume PHP doesn't have 100MB of code like: if( identifier == "substr" ) { return PHP_SUBSTR(...); } else if( ... ) { ... } Ha ha, that would be pretty funny. I hope you have understood my question so far. How do interpreters solve this problem? How can I solve this for my own experimental toy interpreter?

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• How would the 'Model' in a Rails-type webapp be implemented in a functional programming langauge?

  - by ceptorial

  In MVC web development frameworks such as Ruby on Rails, Django, and CakePHP, HTTP requests are routed to controllers, which fetch objects which are usually persisted to a backend database store. These objects represent things like users, blog posts, etc., and often contain logic within their methods for permissions, fetching and/or mutating other objects, validation, etc. These frameworks are all very much object oriented. I've been reading up recently on functional programming and it seems to tout tremendous benefits such as testability, conciseness, modularity, etc. However most of the examples I've seen for functional programming implement trivial functionality like quicksort or the fibonnacci sequence, not complex webapps. I've looked at a few 'functional' web frameworks, and they all seem to implement the view and controller just fine, but largely skip over the whole 'model' and 'persistence' part. (I'm talking more about frameworks like Compojure which are supposed to be purely functional, versus something Lift which conveniently seems to use the OO part of Scala for the model -- but correct me if I'm wrong here.) I haven't seen a good explanation of how functional programming can be used to provide the metaphor that OO programming provides, i.e. tables map to objects, and objects can have methods which provide powerful, encapsulated logic such as permissioning and validation. Also the whole concept of using SQL queries to persist data seems to violate the whole 'side effects' concept. Could someone provide an explanation of how the 'model' layer would be implemented in a functionally programmed web framework?

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• How 'terse' is too terse? -- Practical guidelines for expressing as much intent in as few characters

  - by Christopher Altman

  First, I love writing as little code as possible. I think, and please correct me, one of the golden rules of programming is to express your code in as few of character as possible while maintaining human readability. But I can get a little carried away. I can pack three or four lines into one statement, something like $startDate = $dateTime > time() ? mktime(0,0,0,date('m',time()-86400),date('d',time()*2),2011) : time(); (Note: this is a notional example) I can comprehend the above code when reading it. I prefer 'mushing' it all together because having less lines per page is a good thing to me. So my question: When writing code and thinking about how compact or terse you can express yourself, what are some guidelines you use? Do you write multiple lines because you think it helps other people? Do you write as little as possible, but use comments? Or do you always look for the way to write as little code as possible and enjoy the rewards of compact statements? (Just one slightly off topic comment: I love the Perl one-liners, but that is not what I am talking about here)

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• Are Fortran control characters (carriage control) still implemented in compilers?

  - by CmdrGuard

  In the book Fortran 95/2003 for Scientists and Engineers, there is much talk given to the importance of recognizing that the first column in a format statement is reserved for control characters. I've also seen control characters referred to as carriage control on the internet. To avoid confusion, by control characters, I refer to the characters "1, a blank (i.e. \s), 0, and +" as having an effect on the vertical spacing of output when placed in the first column (character) of a FORMAT statement. Also, see this text-only web page written entirely in fixed-width typeface : Fortran carriage-control (because nothing screams accuracy and antiquity better than prose in monospaced font). I found this page and others like it to be not quite clear. According to Fortran 95/2003 for Scientists and Engineers, failure to recall that the first column is reserved for carriage control can lead to horrible unintended output. Paraphrasing Dave Barry, type the wrong character, and nuclear missiles get fired at Norway. However, when I attempt to adhere to this stern warning, I find that gfortran has no idea what I'm talking about. Allow me to illustrate my point with some example code. I am trying to print out the number Pi: PROGRAM test_format IMPLICIT NONE REAL :: PI = 2 * ACOS(0.0) WRITE (*, 100) PI WRITE (*, 200) PI WRITE (*, 300) PI 100 FORMAT ('1', "New page: ", F11.9) 200 FORMAT (' ', "Single Space: ", F11.9) 300 FORMAT ('0', "Double Space: ", F11.9) END PROGRAM test_format This is the output: 1New page: 3.141592741 Single Space: 3.141592741 0Double Space: 3.141592741 The "1" and "0" are not typos. It appears that gfortran is completely ignoring the control character column. My question, then, is this: Are control characters still implemented in standards compliant compilers or is gfortran simply not standards compliant? For clarity, here is the output of my gfortran -v Using built-in specs. Target: powerpc-apple-darwin9 Configured with: ../gcc-4.4.0/configure --prefix=/sw --prefix=/sw/lib/gcc4.4 --mandir=/sw/share/man --infodir=/sw/share/info --enable-languages=c,c++,fortran,objc,java --with-gmp=/sw --with-libiconv-prefix=/sw --with-ppl=/sw --with-cloog=/sw --with-system-zlib --x-includes=/usr/X11R6/include --x-libraries=/usr/X11R6/lib --disable-libjava-multilib --build=powerpc-apple-darwin9 --host=powerpc-apple-darwin9 --target=powerpc-apple-darwin9 Thread model: posix gcc version 4.4.0 (GCC)

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• What's your preferred pointer declaration style, and why?

  - by Owen

  I know this is about as bad as it gets for "religious" issues, as Jeff calls them. But I want to know why the people who disagree with me on this do so, and hear their justification for their horrific style. I googled for a while and couldn't find a style guide talking about this. So here's how I feel pointers (and references) should be declared: int* pointer = NULL; int& ref = *pointer; int*& pointer_ref = pointer; The asterisk or ampersand goes with the type, because it modifies the type of the variable being declared. EDIT: I hate to keep repeating the word, but when I say it modifies the type I'm speaking semantically. "int* something;" would translate into English as something like "I declare something, which is a pointer to an integer." The "pointer" goes along with the "integer" much more so than it does with the "something." In contrast, the other uses of the ampersand and asterisk, as address-of and dereferencing operators, act on a variable. Here are the other two styles (maybe there are more but I really hope not): int *ugly_but_common; int * uglier_but_fortunately_less_common; Why? Really, why? I can never think of a case where the second is appropriate, and the first only suitable perhaps with something like: int *hag, *beast; But come now... multiple variable declarations on one line is kind of ugly form in itself already.

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