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  • How to lazy load scripts in YUI that accompany ajax html fragments

    - by Chris Beck
    I have a web app with Tabs for Messages and Contacts (think gmail). Each Tab has a Y.on('click') event listener that retrieves an HTML fragment via Y.io() and renders the fragment via node.setContent(). However, the Contact Tab also requires contact.js to enable an Edit button in the fragment. How do I defer the cost of loading contact.js until the user clicks on the Contacts tab? How should contact.js add it's listener to the Edit button? The Complete function of my Tab's on('click') event could serialize Get.script('contact.js') after Y.io('fragment'). However, for better performance, I would prefer to download the script in parallel to downloading the HTML fragment. In that case, I would need to defer adding an event listener to the Edit button until the Edit button is available. This seems like a common RIA design pattern. What is the best way to implement this with YUI? How should I get the script? How should I defer sections of the script until elements in the fragment are available in the DOM?

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  • Webpage data scraping using Java

    - by Gemma
    I am now trying to implement a simple HTML webpage scraper using Java.Now I have a small problem. Suppose I have the following HTML fragment. <div id="sr-h-left" class="sr-comp"> <a class="link-gray-underline" id="compare_header" rel="nofollow" href="javascript:i18nCompareProd('/serv/main/buyer/ProductCompare.jsp?nxtg=41980a1c051f-0942A6ADCF43B802');"> <span style="cursor: pointer;" class="sr-h-o">Compare</span> </a> </div> <div id="sr-h-right" class="sr-summary"> <div id="sr-num-results"> <div class="sr-h-o-r">Showing 1 - 30 of 1,439 matches, The data I am interested is the integer 1.439 shown at the bottom.I am just wondering how can I get that integer out of the HTML. I am now considering using a regular expression,and then use the java.util.Pattern to help get the data out,but still not very clear about the process. I would be grateful if you guys could give me some hint or idea on this data scraping. Thanks a lot.

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  • Problem with load testing Web Service - VSTS 2008

    - by Carlos
    Hello, I have a webtest with makes a simple call to a WebService which looks like that: MyWebService webService = new MyWebService(); webService.Timeout = 180000; webService.myMethod(); I am not using ThinkTimes, also the Run Duration is set to 5 minutes. When I ran this test simulating only 1 user, I check the counters and I found something like that: Tests Total: 4500 Network Interface\Bytes sent (agent machine): 35,500 Then I ran the same tests, but this time simulating 2 users and I got something like that: Tests Total: 2225 Network Interface\Bytes sent (agent machine): 30,500 So when I increased the numbers of users the tests/sec was half than when I use only 1 user and the bytes sent by the agent was also lower. I think it is strange, because it doesn't seems I have a bottleneck in my agent machine since CPU is never higher than 30% and I have over 1.5GB of RAM free, also my network utilization is like 0.5% of its capacity. In order to troubleshot this I ran a test using Step Pattern, the simulated users went from 20 to 800 users. When I check the requests/sec it is practically constant through the whole test, so it is clear there is something in my test or my environment which is preventing the number of requests from gets higher. It would be a expected behavior if the "response time" was getting higher because it would tell me the requests wasn't been processed properly, but the strange thing is the response time is practically constant all the time and it is pretty low actually. I have no idea why my agent can't send more requests when I increase the numbers of users, any help/tip/guess would be really appreciate.

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  • a selective dual command binding converter in WPF?

    - by Jippers
    I'll start off and say I am not using the MVVM pattern for my WPF app. Please forgive me. Right now I have a data template with two buttons, each binds to a different command on the CLR object this data template represents. Both use the same command parameter. Here's an example of the buttons. <Button x:Name="Button1" Command="{Binding Path=Command1}" CommandParameter="{Binding Path=Text, ElementName=TextBox1}" /> <Button x:Name="Button2" Command="{Binding Path=Command2}" CommandParameter="{Binding Path=Text, ElementName=TextBox1}" /> I would like to refactor this into a single button that can perform either command based on a user setting like a boolean in Settings.settings. I don't have access to refactoring the CLR object itself. Also this is a Data Template there isn't codebehind for me to work with. My take is that a converter would be the best bet, but I don't know how I would put that together. The converter would need to take in the CommandParameter, as well as the DataContext so it knows which object to execute the Commands on. Can someone lend me a hand with this? Thanks in advance.

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  • Is F# a good language for card game AI?

    - by Anthony Brien
    I'm writing a Mahjong Game in C# (the Chinese traditional game, not the solitaire kind). While writing the code for the bot player's AI, I'm wondering if a functional language like F# would be a more suitable language than what I currently use which is C# with a lot of Linq. I don't know much about F# which is why I ask here. To illustrate what I try to solve, here's a quick summary of Mahjong: Mahjong plays a bit like Gin Rummy. You have 13 tiles in your hand, and each turn, you draw a tile and discard another one, trying to improve your hand towards a winning Mahjong hand, which consists or 4 sets and a pair. Sets can be a 3 of a kind (pungs), 4 of a kind (kongs) or a sequence of 3 consecutive tiles (chows). You can also steal another player's discard, if it can complete one of your sets. The code I had to write to detect if the bot can declare 3 consecutive tiles set (chow) is pretty tedious. I have to find all the unique tiles in the hand, and then start checking if there's a sequence of 3 tiles that contain that one in the hand. Detecting if the bot can go Mahjong is even more complicated since it's a combination of detecting if there's 4 sets and a pair in his hand. And that's just a standard Mahjong hand. There's also numerous "special" hands that break those rules but are still a Mahjong hand. For example, "13 unique wonders" consists of 13 specific tiles, "Jade Empire" consists of only tiles colored green, etc. In a perfect world, I'd love to be able to just state the 'rules' of Mahjong, and have the language be able to match a set of 13 tiles against those rules to retrieve which rules it fulfills, for example, checking if it's a Mahjong hand or if it includes a 4 of a kind. Is this something F#'s pattern matching feature can help solve?

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  • Should frontend and backend handled by different controllers?

    - by DR
    In my previous learning projects I always used a single controller, but know I wonder if that is good practice or even always possible. In all RESTful Rails tutorials the controllers have a show, an edit and an index view. If an authorized user is logged on, the edit view becomes available and the index view shows additional data manipulation controls, like a delete button or a link to the edit view. Now I have a Rails application which falls exactly into this pattern, but the index view is not reusable: The normal user sees a flashy index page with lots of pictures, complex layout, no Javascript requirement, ... The Admin user index has a completly different minimalistic design, jQuery table and lots of additional data, ... Now I'm not sure how to handle this case. I can think of the following: Single controller, single view: The view is split into two large blocks/partials using an if statement. Single controller, two views: index and index_admin. Two different controllers: BookController and BookAdminController None of this solutions seems perfect, but for now I'm inclined to use the 3rd option. What's the preferred way to do this?

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  • standard way to perform a clean shutdown with Boost.Asio

    - by Timothy003
    I'm writing a cross-platform server program in C++ using Boost.Asio. Following the HTTP Server example on this page, I'd like to handle a user termination request without using implementation-specific APIs. I've initially attempted to use the standard C signal library, but have been unable to find a design pattern suitable for Asio. The Windows example's design seems to resemble the signal library closest, but there's a race condition where the console ctrl handler could be called after the server object has been destroyed. I'm trying to avoid race conditions that cause undefined behavior as specified by the C++ standard. Is there a standard (correct) way to stop the server? So far: #include <csignal> #include <functional> #include <boost/asio.hpp> using std::signal; using boost::asio::io_service; extern "C" { static void handle_signal(int); } namespace { std::function<void ()> sighandler; } void handle_signal(int) { sighandler(); } int main() { io_service s; sighandler = std::bind(&io_service::stop, &s); auto res = signal(SIGINT, &handle_signal); // race condition? SIGINT raised before I could set ignore back if (res == SIG_IGN) signal(SIGINT, SIG_IGN); res = signal(SIGTERM, &handle_signal); // race condition? SIGTERM raised before I could set ignore back if (res == SIG_IGN) signal(SIGTERM, SIG_IGN); s.run(); // reset signals signal(SIGTERM, SIG_DFL); signal(SIGINT, SIG_DFL); // is it defined whether handle_signal can still be in execution at this // point? sighandler = nullptr; }

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  • Can I specify the files to commit in subversion in a file rather than on the command line?

    - by René Nyffenegger
    I have renamed (with svn move) a lot of files in a subversion project. Now, I am trying to commit these on Window's cmd.exe. It seems that I hit a limit (probably by cmd.exe) in that the number of files is too long for the command line to swallow. Now, I thought and hoped that I could list the files to commit in a seperate file that I could specify with the commit command (something like svn ci --files-to-commit=renamed-files.txt -m "Renamed a lot of files" Yet, either such an option does not exist or I am unable to find this. Unfortunately, I cannot do a svn ci . as I have done other changes in the project as well. Neither can I do a svn ci *pattern-of-renamed-files* since this would only check in the added files, not the deleted ones. Before I start checking in the files with smaller chunks of files to check in (and thus increase the revision number uneccesserily without giving a hint as to the 'atomicity' of the operation) I thought I ask if this is indeed impossible to do.

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  • Wpf binding with nested properties

    - by byte
    ViewModel I have a property of type Member called KeyMember. The 'Member' type has an ObservableCollection called Addresses. The Address is composed of two strings - street and postcode . View I have a ListBox whose item source need to be set to ViewModels's KeyMember property and it should display the Street of all the Past Addresses in the collection. Question My ViewModel and View relationship is established properly. I am able to write a data template for the above simple case as below <ListBox ItemsSource="{Binding KeyMember.Addresses}"> <ListBox.ItemTemplate> <DataTemplate DataType="Address"> <TextBlock Text="{Binding Street}"/> </DataTemplate> </ListBox.ItemTemplate> </ListBox> How would I write the DataTemplate if I change KeyMember from type Member to ObservableCollection< Member assuming that the collection has only one element. PS: I know that for multiple elements in collection, I will have to implement the Master-Detail pattern/scenario.

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  • MVC Paging and Sorting Patterns: How to Page or Sort Re-Using Form Criteria

    - by CRice
    What is the best ASP.NET MVC pattern for paging data when the data is filtered by form criteria? This question is similar to: http://stackoverflow.com/questions/1425000/preserve-data-in-net-mvc but surely there is a better answer? Currently, when I click the search button this action is called: [AcceptVerbs(HttpVerbs.Post)] public ActionResult Search(MemberSearchForm formSp, int? pageIndex, string sortExpression) {} That is perfect for the initial display of the results in the table. But I want to have page number links or sort expression links re-post the current form data (the user entered it the first time - persisted because it is returned as viewdata), along with extra route params 'pageIndex' or 'sortExpression', Can an ActionLink or RouteLink (which I would use for page numbers) post the form to the url they specify? <%= Html.RouteLink("page 2", "MemberSearch", new { pageIndex = 1 })%> At the moment they just do a basic redirect and do not post the form values so the search page loads fresh. In regular old web forms I used to persist the search params (MemberSearchForm) in the ViewState and have a GridView paging or sorting event reuse it.

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  • How to allow one thread to mutate an array property while another thread iterates on a copy of the a

    - by Steve918
    I would like to implement an observer pattern in Objective-C where the observer implements an interface similar to SKPaymentTransactionObserver and the observable class just extends my base observable. My observable class looks something like what is below. Notice I'm making copies of the observers before enumeration to avoid throwing an exception . I've tried adding an NSLock around add observers and notify observers, but I run into a deadlock. What would be the proper way to handle concurrency when observers are being added as notifications are being sent? @implementation Observable -(void)notifyObservers:(SEL)selector { @synchronized(self) { NSSet* observer_copy = [observers copy]; for (id observer in observer_copy) { if([observer respondsToSelector: selector]) { [observer performSelector: selector]; } } [observer_copy release]; } } -(void)notifyObservers:(SEL)selector withObject:(id)arg1 withObject:(id)arg2 { @synchronized(self) { NSSet* observer_copy = [observers copy]; for (id observer in observer_copy) { if([observer respondsToSelector: selector]) { [observer performSelector: selector withObject: arg1 withObject: arg2]; } } [observer_copy release]; } } -(void)addObserver:(id)observer { @synchronized(self) { [observers addObject: observer]; } } -(void)removeObserver:(id)observer { @synchronized(self) { [observers removeObject: observer]; } }

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  • How to configure database connection securely

    - by chiccodoro
    Similar but not the same: How to securely store database connection details Securely connecting to database within a application Hi all, I have a C# WinForms application connecting to a database server. The database connection string, including a generic user/pass, is placed in a NHibernate configuration file, which lies in the same directory as the exe file. Now I have this issue: The user that runs the application should not get to know the username/password of the general database user because I don't want him to rummage around in the database directly. Alternatively I could hardcode the connection string, which is bad because the administrator must be able to change it if the database is moved or if he wants to switch between dev/test/prod environments. So long I've found three possibilities: The first referenced question was generally answered by making the file only readable for the user that runs the application. But that's not not enough in my case (the user running the application is a person. The database user/pass are general and shouldn't even be accessible by the person.) The first answer additionally proposed to encrypt the connection data before writing it to the file. With this approach, the administrator is not able anymore to configure the connection string because he cannot encrypt it by hand. The second referenced question provides an approach for this very scenario but it seems very complicated. My questions to you: This is a very general issue, so isn't there any general "how-to-do-it" way, somehow a "design pattern"? Is there some support in .NET's config infrastructure? (optional, maybe out of scope) Can I combine that easily with the NHibernate configuration mechanism?

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  • How do I use the sed command to remove all lines between 2 phrases (including the phrases themselves

    - by fzkl
    I am generating a log from which I want to remove X startup output which looks like this: X.Org X Server 1.7.6 Release Date: 2010-03-17 X Protocol Version 11, Revision 0 Build Operating System: Linux 2.6.31-607-imx51 armv7l Ubuntu Current Operating System: Linux nvidia 2.6.33.2 #1 SMP PREEMPT Mon May 31 21:38:29 PDT 2010 armv7l Kernel command line: mem=448M@0M nvmem=64M@448M mem=512M@512M chipuid=097c81c6425f70d7 vmalloc=320M video=tegrafb console=ttyS0,57600n8 usbcore.old_scheme_first=1 tegraboot=nand root=/dev/nfs ip=:::::usb0:on rw tegra_ehci_probe_delay=5000 smp dvfs tegrapart=recovery:1b80:a00:800,boot:2680:1000:800,environment:3780:40:800,system:38c0:2bc00:800,cache:2f5c0:4000:800,userdata:336c0:c840:800 envsector=3080 Build Date: 23 April 2010 05:19:26PM xorg-server 2:1.7.6-2ubuntu7 (Bryce Harrington <[email protected]>) Current version of pixman: 0.16.4 Before reporting problems, check http://wiki.x.org to make sure that you have the latest version. Markers: (--) probed, (**) from config file, (==) default setting, (++) from command line, (!!) notice, (II) informational, (WW) warning, (EE) error, (NI) not implemented, (??) unknown. (==) Log file: "/var/log/Xorg.0.log", Time: Wed Jun 16 19:52:00 2010 (==) Using config file: "/etc/X11/xorg.conf" (==) Using config directory: "/usr/lib/X11/xorg.conf.d" Is there any way to do this without manually checking pattern for each line?

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  • How to represent and insert into an ordered list in SQL?

    - by Travis
    I want to represent the list "hi", "hello", "goodbye", "good day", "howdy" (with that order), in a SQL table: pk | i | val ------------ 1 | 0 | hi 0 | 2 | hello 2 | 3 | goodbye 3 | 4 | good day 5 | 6 | howdy 'pk' is the primary key column. Disregard its values. 'i' is the "index" that defines that order of the values in the 'val' column. It is only used to establish the order and the values are otherwise unimportant. The problem I'm having is with inserting values into the list while maintaining the order. For example, if I want to insert "hey" and I want it to appear between "hello" and "goodbye", then I have to shift the 'i' values of "goodbye" and "good day" (but preferably not "howdy") to make room for the new entry. So, is there a standard SQL pattern to do the shift operation, but only shift the elements that are necessary? (Note that a simple "UPDATE table SET i=i+1 WHERE i=3" doesn't work, because it violates the uniqueness constraint on 'i', and also it updates the "howdy" row unnecessarily.) Or, is there a better way to represent the ordered list? I suppose you could make 'i' a floating point value and choose values between, but then you have to have a separate rebalancing operation when no such value exists. Or, is there some standard algorithm for generating string values between arbitrary other strings, if I were to make 'i' a varchar? Or should I just represent it as a linked list? I was avoiding that because I'd like to also be able to do a SELECT .. ORDER BY to get all the elements in order.

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  • Using clases in PHP to store function

    - by Artur
    Hello! I need some advise on my PHP code organisation. I need classes where I can store different functions, and I need access to those classes in different parts of my project. Making an object of this classes each time is too sadly, so I've found a two ways have to solve it. First is to use static methods, like class car { public static $wheels_count = 4; public static function change_wheels_count($new_count) { car::$wheels_count = $new_count; } } Second is to use singleton pattern: class Example { // Hold an instance of the class private static $instance; // The singleton method public static function singleton() { if (!isset(self::$instance)) { $c = __CLASS__; self::$instance = new $c; } return self::$instance; } } But author of the article about singletons said, that if I have too much singletons in my code I should reconstruct it. But I need a lot of such classes. Can anybody explain prons and cons of each way? Which is mostly used? Are there more beautiful ways?

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  • How can I validate/secure/authenticate a JavaScript-based POST request?

    - by Bungle
    A product I'm helping to develop will basically work like this: A Web publisher creates a new page on their site that includes a <script> from our server. When a visitor reaches that new page, that <script> gathers the text content of the page and sends it to our server via a POST request (cross-domain, using a <form> inside of an <iframe>). Our server processes the text content and returns a response (via JSONP) that includes an HTML fragment listing links to related content around the Web. This response is cached and served to subsequent visitors until we receive another POST request with text content from the same URL, at which point we regenerate a "fresh" response. These POSTs only happen when our cached TTL expires, at which point the server signifies that and prompts the <script> on the page to gather and POST the text content again. The problem is that this system seems inherently insecure. In theory, anyone could spoof the HTTP POST request (including the referer header, so we couldn't just check for that) that sends a page's content to our server. This could include any text content, which we would then use to generate the related content links for that page. The primary difficulty in making this secure is that our JavaScript is publicly visible. We can't use any kind of private key or other cryptic identifier or pattern because that won't be secret. Ideally, we need a method that somehow verifies that a POST request corresponding to a particular Web page is authentic. We can't just scrape the Web page and compare the content with what's been POSTed, since the purpose of having JavaScript submit the content is that it may be behind a login system. Any ideas? I hope I've explained the problem well enough. Thanks in advance for any suggestions.

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  • what kind of relationship is there between a common wall and the rooms that located next to it?

    - by siamak
    I want to know whats the Relationship between a common wall (that are located In an adjoining room ) and the rooms. As i know the relationship between a room and its walls is Composition not Aggregation (am i right ?) And according to the definition of Composition the contained object can't be shared between two containers, whereas in aggregation it is possible. now i am confused that whats the best modeling approach to represent the relationship between a common wall and the rooms located next to it ? It would be highly Appreciated if you could provide your advices with some code. |--------|--------| Approch1: (wall class ---- room class) /Composition Approach2: wall class ----- room class /Aggregation Approch3: we have a wall class and a Common wall class , Common wall class inherits from wall class adjoining room class ---- (1) Common wall class /Aggregation adjoining room class ---- (6) wall class / composition Approach4: I am a developer not a designer :) so this is my idea : class Room { private wall _firstwall ; private wall _secondtwall; private wall _thirdwall ; private wall _commonwall ; public Room( CommonWall commonwall) { _firstwall=new Wall(); _secondtwall=new Wall(); _thirdwall=new Wall(); _commonwall=commonwall; } } Class CommonWall:Wall { //... } // in somewher : static void main() { Wall _commonWall=new Wall(); Room room1=new Room(_commonWall); Room room2=new Room(_commonWall); Room [] adjacentRoom =new Room[2]{room1,room2}; } Edit 1: I think this is a clear question but just for more clarification : The point of the question is to find out whats the best pattern or approach to model a relationship for an object that is a component of two other objects in the same time. and about my example : waht i mean by a "room" ?,surely i mean an enclosed square room with 4 walls and one door.but in this case one of these walls is a common wall and is shared between two adjacent rooms.

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  • Disposing underlying object from finalizer in an immutable object

    - by Juan Luis Soldi
    I'm trying to wrap around Awesomium and make it look to the rest of my code as close as possible to NET's WebBrowser since this is for an existing application that already uses the WebBrowser. In this library, there is a class called JSObject which represents a javascript object. You can get one of this, for instance, by calling the ExecuteJavascriptWithResult method of the WebView class. If you'd call it like myWebView.ExecuteJavascriptWithResult("document", string.Empty).ToObject(), then you'd get a JSObject that represents the document. I'm writing an immutable class (it's only field is a readonly JSObject object) called JSObjectWrap that wraps around JSObject which I want to use as base class for other classes that would emulate .NET classes such as HtmlElement and HtmlDocument. Now, these classes don't implement Dispose, but JSObject does. What I first thought was to call the underlying JSObject's Dispose method in my JSObjectWrap's finalizer (instead of having JSObjectWrap implement Dispose) so that the rest of my code can stay the way it is (instead of having to add using's everywhere and make sure every JSObjectWrap is being properly disposed). But I just realized if more than two JSObjectWrap's have the same underlying JSObject and one of them gets finalized this will mess up the other JSObjectWrap. So now I'm thinking maybe I should keep a static Dictionary of JSObjects and keep count of how many of each of them are being referenced by a JSObjectWrap but this sounds messy and I think could cause major performance issues. Since this sounds to me like a common pattern I wonder if anyone else has a better idea.

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  • UNIX-style RegExp Replace running extremely slowly under windows. Help? EDIT: Negative lookahead ass

    - by John Sullivan
    I'm trying to run a unix regEXP on every log file in a 1.12 GB directory, then replace the matched pattern with ''. Test run on a 4 meg file is took about 10 minutes, but worked. Obviously something is murdering performance by several orders of magnitude. Find: ^(?!.*155[0-2][0-9]{4}\s.*).*$ -- NOTE: match any line NOT starting 155[0-2]NNNN where in is a number 0-9. Replace with: ''. Is there some justifiable reason for my regExp to take this long to replace matching text, or is the program I am using (this is windows / a program called "grepWin") most likely poorly optimized? Thanks. UPDATE: I am noticing that searching for ^(155[0-2]).$ takes ~7 seconds in a 5.6 MB file with 77 matches. Adding the Negative Lookahead Assertion, ?=, so that the regExp becomes ^(?!155[0-2]).$ is causing it to take at least 5-10 minutes; granted, there will be thousands and thousands of matches. Should the negative lookahead assertion be extremely detrimental to performance, and/or a large quantity of matches?

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  • Convert pre-IEEE-574 C++ floating-point numbers to/from C#

    - by Richard Kucia
    Before .Net, before math coprocessors, before IEEE-574, Microsoft defined a bit pattern for floating-point numbers. Old versions of the C++ compiler happily used that definition. I am writing a C# app that needs to read/write such floating-point numbers in a file. How can I do the conversions between the 2 bit formats? I need conversion methods in both directions. This app is going to run in a PocketPC/WinCE environment. Changing the structure of the file is out-of-scope for this project. Is there a C++ compiler option that instructs it to use the old FP format? That would be ideal. I could then exchange data between the C# code and C++ code by using a null-terminated text string, and the C++ methods would be simple wrappers around sprintf and atof functions. At the very least, I'm hoping someone can reply with the bit definitions for the old FP format, so I can put together a low-level bit manipulation algorithm if necessary. Thanks.

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  • Database for Python Twisted

    - by Will
    There's an API for Twisted apps to talk to a database in a scalable way: twisted.enterprise.dbapi The confusing thing is, which database to pick? The database will have a Twisted app that is mostly making inserts and updates and relatively few selects, and then other strictly-read-only clients that are accessing the database directly making selects. (The read-only users are not necessarily selecting the data that the Twisted app is inserting; its not as though the database is being used as a message-queue) My understanding - which I'd like corrected/adviced - is that: Postgres is a great DB, but all the Python bindings - and there is a confusing maze of them - are abandonware There is psycopg2, but that makes a lot of noise about doing its own connection-pooling and things; does this co-exist gracefully/usefully/transparently with the Twisted async database connection pooling and such? SQLLite is a great database for little things but if used in a multi-user way it does whole-database locking, so performance would suck in the usage pattern I envisage MySQL - after the Oracle takeover, who'd want to adopt it now or adopt a fork? Is there anything else out there?

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  • Use continue or Checked Exceptions when checking and processing objects

    - by Johan Pelgrim
    I'm processing, let's say a list of "Document" objects. Before I record the processing of the document successful I first want to check a couple of things. Let's say, the file referring to the document should be present and something in the document should be present. Just two simple checks for the example but think about 8 more checks before I have successfully processed my document. What would have your preference? for (Document document : List<Document> documents) { if (!fileIsPresent(document)) { doSomethingWithThisResult("File is not present"); continue; } if (!isSomethingInTheDocumentPresent(document)) { doSomethingWithThisResult("Something is not in the document"); continue; } doSomethingWithTheSucces(); } Or for (Document document : List<Document> documents) { try { fileIsPresent(document); isSomethingInTheDocumentPresent(document); doSomethingWithTheSucces(); } catch (ProcessingException e) { doSomethingWithTheExceptionalCase(e.getMessage()); } } public boolean fileIsPresent(Document document) throws ProcessingException { ... throw new ProcessingException("File is not present"); } public boolean isSomethingInTheDocumentPresent(Document document) throws ProcessingException { ... throw new ProcessingException("Something is not in the document"); } What is more readable. What is best? Is there even a better approach of doing this (maybe using a design pattern of some sort)? As far as readability goes my preference currently is the Exception variant... What is yours?

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  • Using JavaCC to infer semantics from a Composite tree

    - by Skice
    Hi all, I am programming (in Java) a very limited symbolic calculus library that manages polynomials, exponentials and expolinomials (sums of elements like "x^n * e^(c x)"). I want the library to be extensible in the sense of new analytic forms (trigonometric, etc.) or new kinds of operations (logarithm, domain transformations, etc.), so a Composite pattern that represent the syntactic structure of an expression, together with a bunch of Visitors for the operations, does the job quite well. My problem arise when I try to implement operations that depends on the semantics more than on the syntax of the Expression (like integrals, for instance: there are a lot of resolution methods for specific classes of functions, but these same classes can be represented with more than a single syntax). So I thought I need something to "parse" the Composite tree to infer its semantics in order to invoke the right integration method (if any). Someone pointed me to JavaCC, but all the examples I've seen deal only with string parsing; so, I don't know if I'm digging in the right direction. Some suggestions? (I hope to have been clear enough!)

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  • Display image background fully for last repeat in a div

    - by Stiggler
    I have a 700x300 background repeating seamlessly under the main content-div. Now I'd like to attach a div at the bottom of the content-div, containing a continuation-to-end of the background image, connecting seamlessly with the background above it. Due to the nature of the pattern, unless the full 300px height of the background image is visible in the last repeat of the content-div's backround, the background in the div below won't seamlessly connect. Basically, I need the content div's height to be a multiple of 300px under all circumstances. What's a good approach to this sort of problem? I've tried resizing the content-div on loading the page, but this only works as long as the content div doesn't contain any resizing, dynamic content, which is not my case: function adjustContentHeight() { // Setting content div's height to nearest upper multiple of column backgrounds height, // forcing it not to be cut-off when repeated. var contentBgHeight = 300; var contentHeight = $("#content").height(); var adjustedHeight = Math.ceil(contentHeight / contentBgHeight); $("#content").height(adjustedHeight * contentBgHeight); } $(document).ready(adjustContentHeight); What I'm looking for there is a way to respond to a div resizing event, but there doesn't seem to be such a thing. Also, please assume I have no access to the JS controlling the resizing of content in the content-div, though this is potentially a way of solving the problem. Another potential solution I was thinking off was to offset the background image in the bottom div by a certain amount depending on the height of the content-div. Again, the missing piece seems to be the ability to respond to a resize event.

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  • Null Safe dereferencing in Java like ?. in Groovy using Maybe monad

    - by Sathish
    I'm working on a codebase ported from Objective C to Java. There are several usages of method chaining without nullchecks dog.collar().tag().name() I was looking for something similar to safe-dereferencing operator ?. in Groovy instead of having nullchecks dog.collar?.tag?.name This led to Maybe monad to have the notion of Nothing instead of Null. But all the implementations of Nothing i came across throw exception when value is accessed which still doesn't solve the chaining problem. I made Nothing return a mock, which behaves like NullObject pattern. But it solves the chaining problem. Is there anything wrong with this implementation of Nothing? [http://github.com/sathish316/jsafederef/blob/master/src/s2k/util/safederef/Nothing.java] As far as i can see 1. It feels odd to use mocking library in code 2. It doesn't stop at the first null. 3. How do i distinguish between null result because of null reference or name actually being null? How is it distinguished in Groovy code?

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