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  • C++ Templates: Convincing self against code bloat

    - by ArunSaha
    I have heard about code bloats in context of C++ templates. I know that is not the case with modern C++ compilers. But, I want to construct an example and convince myself. Lets say we have a class template< typename T, size_t N > class Array { public: T * data(); private: T elems_[ N }; }; template< typename T, size_t N > T * Array<T>::data() { return elems_; } Further, let's say types.h contains typedef Array< int, 100 > MyArray; x.cpp contains MyArray ArrayX; and y.cpp contains MyArray ArrayY; Now, how can I verify that the code space for MyArray::data() is same for both ArrayX and ArrayY? What else I should know and verify from this (or other similar simple) examples? If there is any g++ specific tips, I am interested for that too. PS: Regarding bloat, I am concerned even for the slightest of bloats, since I come from embedded context.

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  • Why is -webkit-keyframes not working in my SASS mixin?

    - by Tintin81
    I have this SASS mixin that should make a button flash: @mixin background_animation($color) { -webkit-animation: backgroundAnimation 800ms infinite; @-webkit-keyframes backgroundAnimation { 0% {background-color: $color;} 50% {background-color: red;} 100% {background-color: $color;} } } I am using it like this: @include background_animation(#000000); However, it's not working. The background color of the button won't flash. Can anybody tell me what I'm missing here? P.S. The code works fine when not including it as a mixin. The generated CSS looks like this: -webkit-animation-delay: 0s; -webkit-animation-direction: normal; -webkit-animation-duration: 0.800000011920929s; -webkit-animation-fill-mode: none; -webkit-animation-iteration-count: infinite; -webkit-animation-name: backgroundAnimation; -webkit-animation-timing-function: cubic-bezier(0.25, 0.1, 0.25, 1); ... other rules omitted for brevity

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  • Spork doesnt reload code

    - by there-is-no-spoon
    I am using following gems and ruby-1.9.3-p194: rails 3.2.3 rspec-rails 2.9.0 spork 1.0.0rc2 guard-spork 0.6.1 Full list of used gems is available in this Gemfile.lock or Gemfile. And I am using this configuration files: Guardfile .rspec spec_helper.rb factories.rb If I modify any model (or custom validator in app/validators etc) reloading code doesnt works. I mean when I run specs (hit Enter on guard console) Spork contain "old code" and I got obsolete error messages. But when I manually restart Guard and Spork (CTRC-C CTRL-d guard) everything works fine. But it is getting tired after few times. Questions: Can somebody look at my config files please and fix error which block updating code. Or maybe this is an issue of newest Rails version? PS This problem repeats and repeats over some projects (and on some NOT). But I haven't figured out yet why this is happens. PS2 Perhaps this problem is something to do with ActiveAdmin? When I change file in app/admin code is reloaded.

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  • How can I output my MySQL data into following structures?

    - by sky
    Here is the question, how can I output MySQL data into format like : userAge, userMid are the column name, table name Users. <script type="text/javascript"> userAge = new Array('21','36','20'), userMid = new Array('liuple','anhu','jacksen'); </script> Which I'll be using later with following code : var html = ' <table class="map-overlay"> <tr> <td class="user">' + '<a class="username" href="/' + **userMid[index]** + '" target="_blank"><img alt="" src="' + getAvatar(signImgList[index], '72x72') + '"></a><br> <a class="username" href="/' + **userMid[index]** + '" target="_blank">' + userNameList[index] + '</a><br> <span class="info">' + **userSex[index]** + ' ' + **userAge[index]** + '?<br> ' + cityList[index] + '</span>' + '</td> <td class="content">' + picString + somethings[index] + '<br> <span class="time">' + timeList[index] + picTips + '</span></td> </tr> </table> '; PS: I Just been told that i coulnt use JSON to output that format, so i have no idea now .< Thanks!

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  • HashMap Memory Leak because of Dynamic Array

    - by Jake M
    I am attempting to create my own HashMap to understand how they work. I am using an array of Linked Lists to store the values(strings) in my hashmap. I am creating the array like this: Node** list; Instead of this: Node* list[nSize]; This is so the array can be any size at runtime. But I think I am getting a memory leak because of how I am doing this. I dont know where the error is but when I run the following simple code the .exe crashes. Why is my application crashing and how can I fix it? Note: I am aware that using a vector would be much better than an array but this is just for learning and I want to challenge myself to create the hashmap using a 'Dynamic' Array. PS: is that the correct term(Dynamic Array) for the kind of array I am using? struct Node { // to implement }; class HashMap { public: HashMap(int dynSize) { *list = new Node[dynSize]; size = dynSize; for (int i=0; i<size; i++) list[i] = NULL; cout << "END\n"; } ~HashMap() { for (int i=0; i<size; i++) delete list[i]; } private: Node** list; // I could use a vector here but I am experimenting with a pointer to an array(pointer), also its more elegant int size; }; int main() { // When I run this application it crashes. Where is my memory leak? HashMap h(5); system("PAUSE"); return 0; }

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  • Noise with multi-threaded raytracer

    - by herber88
    This is my first multi-threaded implementation, so it's probably a beginners mistake. The threads handle the rendering of every second row of pixels (so all rendering is handled within each thread). The problem persists if the threads render the upper and lower parts of the screen respectively. Both threads read from the same variables, can this cause any problems? From what I've understood only writing can cause concurrency problems... Can calling the same functions cause any concurrency problems? And again, from what I've understood this shouldn't be a problem... The only time both threads write to the same variable is when saving the calculated pixel color. This is stored in an array, but they never write to the same indices in that array. Can this cause a problem? Multi-threaded rendered image (Spam prevention stops me from posting images directly..) Ps. I use the exactly same implementation in both cases, the ONLY difference is a single vs. two threads created for the rendering.

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  • Chache problem running two consecutive HTTP GET requests from an APP1 to an APP2

    - by user502052
    I use Ruby on Rails 3 and I have 2 applications (APP1 and APP2) working on two subdomains: app1.domain.local app2.domain.local and I am tryng to run two consecutive HTTP GET requests from APP1 to APP2 like this: Code in APP1 (request): response1 = Net::HTTP.get( URI.parse("http://app2.domain.local?test=first&id=1") ) response2 = Net::HTTP.get( URI.parse("http://app2.domain.local/test=second&id=1") ) Code in APP2 (response): respond_to do |format| if <model_name>.find(params[:id]).<field_name> == "first" <model_name>.find(params[:id]).update_attribute ( <field_name>, <field_value> ) format.xml { render :xml => <model_name>.find(params[:id]).<field_name> } elsif <model_name>.find(params[:id]).<field_name> == "second" format.xml { render :xml => <model_name>.find(params[:id]).<field_name> } end end After the first request I get the correct XML (response1 is what I expect), but on the second it isn't (response2 isn't what I expect). Doing some tests I found that the second time that <model_name>.find(params[:id]).<field_name> run (for the elsif statements) it returns always a blank value so that the code in the elseif statement is never run. Is it possible that the problem is related on caching <model_name>.find(params[:id]).<field_name>? P.S.: I read about eTag and Conditional GET, but I am not sure that I must use that approach. I would like to keep all simple.

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  • Complex sorting on MySQL database

    - by ChrisR
    I'm facing the following situation. We've got an CMS with an entity with translations. These translations are stored in a different table with a one-to-many relationship. For example newsarticles and newsarticle_translations. The amount of available languages is dynamically determined by the same CMS. When entering a new newsarticle the editor is required to enter at least one translation, which one of the available languages he chooses is up to him. In the newsarticle overview in our CMS we would like to show a column with the (translated) article title, but since none of the languages are mandatory (one of them is mandatory but i don't know which one) i don't really know how to construct my mysql query to select a title for each newsarticle, regardless of the entered language. And to make it all a little harder, our manager asked for the possibilty to also be able to sort on title, so fetching the translations in a separate query is ruled out as far as i know. Anyone has an idea on how to solve this in the most efficient way? Here are my table schema's it it might help > desc news; +-----------------+----------------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+----------------+------+-----+-------------------+----------------+ | id | int(10) | NO | PRI | NULL | auto_increment | | category_id | int(1) | YES | | NULL | | | created | timestamp | NO | | CURRENT_TIMESTAMP | | | user_id | int(10) | YES | | NULL | | +-----------------+----------------+------+-----+-------------------+----------------+ > desc news_translations; +-----------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | enabled | tinyint(1) | NO | | 0 | | | news_id | int(1) unsigned | NO | | NULL | | | title | varchar(255) | NO | | | | | summary | text | YES | | NULL | | | body | text | NO | | NULL | | | language | varchar(2) | NO | | NULL | | +-----------------+------------------+------+-----+---------+----------------+ PS: i've though about subqueries and coalesce() solutions but those seem rather dirty tricks, wondering if something better is know that i'm not thinking of?

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  • problem with "select new Object ... join ... where"

    - by jacob
    Hi, I'm having a problem with an HQL query Three classes ClassOne is my BusinessObject public class ClassOne { private int id; private int status; private Set<ClassTwo> classTwos; + other fields/getters/setters/constructor etc } ClassTwo is referenced in a set of ClassOne and is kind of the history of an object of ClassOne public class ClassTwo { private int id; private int oldStatus; private int newStatus; private String message; //+ getters/setters/constructor etc } ClassThree is my DTO/VO with just one classTwo (not the whole history) public class ClassThree { private int id; private int status; private ClassTwo classTwo; public ClassThree(int pId, int pStatus, ClassTwo pClassTwo) { id=pId; status=pStatus; classTwo=pClassTwo; } //+ getters/setters etc } Now I'd like to create an HQL query like this: I'd like to get all objects of ClassThree with a certain status and if it exists the newest ClassTwo with a certain newStatus. For example: I'd like to get all the DTOs (ClassThree) of ClassOne whose status is now 1, but earlier in their history it has been 2 and I'd like to have the latest ClassTwo object which has 2 as newStatus. SELECT new ClassThree(c1.id, c1.status, c2) FROM ClassOne c1 LEFT JOIN c1.classtwos c2 (...) and (...) is where I don't know what to do, I'm not even sure if it's a join / join fetch Looked around and tried quite a lot already, but no clue. Especially with the join fetch I get some Hibernate errors like org.hibernate.QueryException: query specified join fetching, but the owner of the fetched association was not present in the select list. Fetching the BusinessObject like that is no problem SELECT distinct(c1) FROM ClassOne c1 LEFT OUTER JOIN FETCH c1.classtwos c2 and I get the ClassTwos as my field. Thanks in advance, Jacob P.S.: One thing might be important, ClassTwo has no reference to ClassOne!!

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  • Indexing table with duplicates MySQL/MSSQL with millions of records

    - by Tesnep
    I need help in indexing in MySQL. I have a table in MySQL with following rows: ID Store_ID Feature_ID Order_ID Viewed_Date Deal_ID IsTrial The ID is auto generated. Store_ID goes from 1 - 8. Feature_ID from 1 - let's say 100. Viewed Date is Date and time on which the data is inserted. IsTrial is either 0 or 1. You can ignore Order_ID and Deal_ID from this discussion. There are millions of data in the table and we have a reporting backend that needs to view the number of views in a certain period or overall where trial is 0 for a particular store id and for a particular feature. The query takes the form of: select count(viewed_date) from theTable where viewed_date between '2009-12-01' and '2010-12-31' and store_id = '2' and feature_id = '12' and Istrial = 0 In MSSQL you can have a filtered index to use for Istrial. Is there anything similar to this in MySQL? Also, Store_ID and Feature_ID have a lot of duplicate data. I created an index using Store_ID and Feature_ID. Although this seems to have decreased the search period, I need better improvement than this. Right now I have more than 4 million rows. To search for a particular query like the one above, it looks at 3.5 million rows in order to give me the count of 500k rows. PS. I forgot to add view_date filter in the query. Now I have done this.

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  • Drawing line graphics leads Flash to spiral out of control!

    - by drpepper
    Hi, I'm having problems with some AS3 code that simply draws on a Sprite's Graphics object. The drawing happens as part of a larger procedure called on every ENTER_FRAME event of the stage. Flash neither crashes nor returns an error. Instead, it starts running at 100% CPU and grabs all the memory that it can, until I kill the process manually or my computer buckles under the pressure when it gets up to around 2-3 GB. This will happen at a random time, and without any noticiple slowdown beforehand. WTF? Has anyone seen anything like this? PS: I used to do the drawing within a MOUSE_MOVE event handler, which brought this problem on even faster. PPS: I'm developing on Linux, but reproduced the same problem on Windows. UPDATE: You asked for some code, so here we are. The drawing function looks like this: public static function drawDashedLine(i_graphics : Graphics, i_from : Point, i_to : Point, i_on : Number, i_off : Number) : void { const vecLength : Number = Point.distance(i_from, i_to); i_graphics.moveTo(i_from.x, i_from.y); var dist : Number = 0; var lineIsOn : Boolean = true; while(dist < vecLength) { dist = Math.min(vecLength, dist + (lineIsOn ? i_on : i_off)); const p : Point = Point.interpolate(i_from, i_to, 1 - dist / vecLength); if(lineIsOn) i_graphics.lineTo(p.x, p.y); else i_graphics.moveTo(p.x, p.y); lineIsOn = !lineIsOn; } } and is called like this (m_graphicsLayer is a Sprite): m_graphicsLayer.graphics.clear(); if (m_destinationPoint) { m_graphicsLayer.graphics.lineStyle(2, m_fixedAim ? 0xff0000 : 0x333333, 1); drawDashedLine(m_graphicsLayer.graphics, m_initialPos, m_destinationPoint, 10, 10); }

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  • Iphone: XML image problem

    - by avanadra
    Hi! I have a question about parsing XML and putting it into a table. I parsed the following elements from a RSS feed : title, dc:creator and enclosure url (= an image). The parsing is working, i can see everything showing up in the console. But when i try to load everything into the tablecell, everything shows up except for the image. So i figured that the problem must be in the CellForRowatIndexPath method in the RootViewController.m ( or in the TableCell.m) What am i doing wrong? Please help! Ive been struggling for days with this and just cant seem to figure it out! Heres the CellForRowatIndexPath: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; WerkTableCell *cell = (WerkTableCell *) [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { [[NSBundle mainBundle] loadNibNamed:@"WerkCell" owner:self options:nil]; cell =self.werkCell; } // Configure the cell. NSMutableArray *cont= [xmlcont items];// is niet in tablevb v. PS ItemData *current =[cont objectAtIndex:indexPath.row]; cell.titelLabel.text = [current titel]; cell.makerLabel.text = [current maker]; cell.thumbImage.image = [UIImage imageNamed:[current image]]; return cell; }

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  • paypal_adaptive gem in Rails: Dynamic Receiver "Population" (Chained Payments)

    - by Jmlevick
    Note: I didn't find a better title for this O.o Hello, Humm... Look, what I want to do is to have a Rails app where a visitor can click a button/link to make a "special" chained payment using Paypal; Currently I have a Users registration form that has one field for the user to enter his/her paypal account email, and as I saw here: http://marker.to/XGg9MR it is possible to specify the primary reciever and the secondary ones by adding such info in a controller action when using the paypal_adaptive gem in a rails app. The thing is, I don't want to hard code the secondary reciever as I need to specify a different secondary reciever from time to time, (being specific my primary reciever will always be the same, but depending on what button/link the visitor clicks, the secondary one is going to change) and I want that secondary reciever email to be the paypal e-mail account from one of the registered users when the visitor clicks on their specific button/link... My question is: Is it possible to create such enviroment functionality in my app using the current implementation of the paypal_adaptive gem? Could someone point me in the right direction on how to accomplish such thing? I'm still learning rails and also I'm really new in the paypal handling universe with this framework! XD P.S. Thanks! :)

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  • Are there any changes in the licensing of Visual Studio 2013 Express editions?

    - by Ramón García-Pérez
    As was going through reading the license.htm file provided as part of the VS2013_RTM_WebExp_ENU.iso offline installation media for the Visual Studio 2013 Express for Web, section 6 reads as follows: 6. PACKAGE MANAGER AND THIRD PARTY SOFTWARE INSTALLATION FEATURES. The software includes the following features (each a “Feature”), each of which enables you to obtain software applications or packages through the Internet from other sources: Extension Manager, New Project Dialog, Web Platform Installer, and Microsoft NuGet-Based Package Manager. Those software applications and packages are offered and distributed in some cases by third parties and in some cases by Microsoft, but each such application or package is under its own license terms. Microsoft is not developing, distributing or licensing any of the third-party applications or packages to you, but instead, as a convenience, enables you to use the Features to access or obtain those applications or packages directly from the third-party application or package providers. By using the Features, you acknowledge and agree that: you are obtaining the applications or packages from such third parties and under separate license terms applicable to each application or package (including, with respect to the package-manager Features, any terms applicable to software dependencies that may be included in the package); MICROSOFT MAKES NO REPRESENTATIONS, WARRANTIES OR GUARANTEES AS TO THE FEED OR GALLERY URL, ANY FEEDS OR GALLERIES FROM SUCH URL, THE INFORMATION CONTAINED THEREIN, OR ANY SOFTWARE APPLICATIONS OR PACKAGES REFERENCED IN OR ACCESSED BY YOU THROUGH SUCH FEEDS OR GALLERIES. MICROSOFT GRANTS YOU NO LICENSE RIGHTS FOR THIRD-PARTY SOFTWARE APPLICATIONS OR PACKAGES THAT ARE OBTAINED USING THE FEATURES. Are there any changes in the licensing of Visual Studio 2013 Express editions? If so, does this means that Visual Studio extensions installation in Express Editions is now allowed? PS: Previous versions of the Express editions did not allow the installation of extensions as per "EULA/TOS" discussed here: Limitations of Visual Studio 2012 Express Desktop

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  • Spring Data Neo4J @Indexed(unique = true) not working

    - by Markus Lamm
    I'm new to Neo4J and I have, probably an easy question. There're NodeEntitys in my application, a property (name) is annotated with @Indexed(unique = true) to achieve the uniqueness like I do in JPA with @Column(unique = true). My problem is, that when I persist an entity with a name that already exists in my graph, it works fine anyway. But I expected some kind of exception here...?! Here' s an overview over basic my code: @NodeEntity public abstract class BaseEntity implements Identifiable { @GraphId private Long entityId; ... } public class Role extends BaseEntity { @Indexed(unique = true) private String name; ... } public interface RoleRepository extends GraphRepository<Role> { Role findByName(String name); } @Service public class RoleServiceImpl extends BaseEntityServiceImpl<Role> implements { private RoleRepository repository; @Override @Transactional public T save(final T entity) { return getRepository().save(entity); } } And this is my test: @Test public void testNameUniqueIndex() { final List<Role> roles = Lists.newLinkedList(service.findAll()); final String existingName = roles.get(0).getName(); Role newRole = new Role.Builder(existingName).build(); newRole = service.save(newRole); } That's the point where I expect something to go wrong! How can I ensure the uniqueness of a property, without checking it for myself?? THANKS IN ADVANCE FOR ANY IDEAS!! P.S.: I'm using neo4j 1.8.M07, spring-data-neo4j 2.1.0.BUILD-SNAPSHOT and Spring 3.1.2.RELEASE.

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  • Actionscript - combining AS2 assets into a single SWF

    - by Justin Bachorik
    Hi guys, I have a flash project that I'm trying to export as a single SWF. There's a main SWF file that loads about 6 other SWFs, and both the main and the child SWFs reference other external assets (images, sounds, etc). I'd like to package everything as a single .swf file so I don't have to tote the other assets around with the .swf. All the coding is done in the timeline, but the assets haven't been imported into the Flash Authoring environment and I don't have time to do that right now (there are too many references to them everywhere). I'm hoping that there's just an option I'm missing that allows this sort of packaged export, but I haven't found anything like that. I don't have access to Flex or mxmlc (and as the AS is timeline-based, they wouldn't necessarily help me). Any thoughts? Thanks! PS...if there's no way of doing exactly what I'm saying, I could deal with having all the assets in a "assets" folder or something like that, so I'd just be toting around main.swf and an assets folder. The problem here is that all the references to the assets assume that they're in the same folder as the main.swf file, so everything's assumed to be local...is there a way to change the scope of all external references in Flash (so, for example, all local references in the code are actually searched in /assets)?

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  • Getting visitors country from their IP

    - by Ali Abdulkarim Salem
    i want to get visitors country via their IP.. right now I'm using this ( http://api.hostip.info/country.php?ip=...... ) here's my code <?php if (isset($_SERVER['HTTP_CLIENT_IP'])) { $real_ip_adress = $_SERVER['HTTP_CLIENT_IP']; } if (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) { $real_ip_adress = $_SERVER['HTTP_X_FORWARDED_FOR']; } else { $real_ip_adress = $_SERVER['REMOTE_ADDR']; } $cip = $real_ip_adress; $iptolocation = 'http://api.hostip.info/country.php?ip=' . $cip; $creatorlocation = file_get_contents($iptolocation); ?> Well, it's working properly, but the thing is, this returns the country code like US or CA., and not the whole country name like United States or Canada So, is there any good alternative to hostip.info offers this? I know that I can just write some code that will eventually turn this two letters to whole country name, but I'm just too lazy to write a code that contains all countries... P.S: For some reason I don't want to use any ready made CSV file or any code that will grab this information for me, something like ip2country ready made code and CSV.

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  • Help Redirecting A Page to Another Page with adverts for 5 seconds, and then redirecting to another page.

    - by XcodeDev
    Hey, I am trying to redirect a page to another page, and that was working successfully. However I am trying to redirect the first page to another page with adverts. This page will then redirect to another page after five seconds. I am trying to do that by doing this: <?php include('ads.php'); ?> <?php sleep(2); $url = $_GET['url']; header("Location: ".$url.""); exit; ?> However it is showing the advert in ads.php perfectly, but it is not redirecting after five seconds. I am receiving this error in my web browser: Warning: Cannot modify header information - headers already sent by (output started at /home/nucleusi/public_html/adverts/ads.php:1) in /home/nucleusi/public_html/adverts/index.php on line 7 A typical link I would be redirecting to would be this: http://nucleusiphone.com/adverts/index.php/?url=http%3A%2F%2Fitunes.apple.com%2Fmx%2Falbum%2Fstill-got-the-blues%2Fid14135178%3Fi%3D14135158 Thanks in advanced. PS. I don't know any php so any code helps!

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  • auto div height

    - by Geln
    <html><head><title>Test</title> <style> .main{width:600px;border:1px solid red; } .main .left{background:lightblue; width:100px;clear:both; float:left;} .main .right{margin-left:100px;background:lightyellow; } </style> </head><body> <div class="main"> <div class="left"> title </div> <div class="right"> <div id="item">item</div> <div id="item">item</div> <div id="item">item</div> <div id="item">item</div> <div id="item">item</div> <div id="item">item</div> <div id="item">item</div> </div> </div> </body></html> How to change the CSS to make the page display like the dialog shows? PS,I think it's a way that to make the "left" div's height auto expend when the height of the "right" div or parent div expend, but I don't know how.

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  • How to implement a grapher in C#

    - by iansinke
    So I'm writing a graphing calculator. So far I have a semi-functional grapher, however, I'm having a hard time getting a good balance between accurate graphs and smooth looking curves. The current implementation (semi-pseudo-code) looks something like this: for (float i = GraphXMin; i <= GraphXMax; i++) { PointF P = new PointF(i, EvaluateFunction(Function, i) ListOfPoints.Add(P) } Graphics.DrawCurve(ListOfPoints) The problem with this is since it only adds a point at every integer value, graphs end up distorted when their turning points don't fall on integers (e.g. sin(x)^2). I tried incrementing i by something smaller (like 0.1), which works, but the graph looks very rough. I am using C# and GDI+. I have SmoothingMethod set to AntiAlias, so that's not the problem, as you can see from the first graph. Is there some sort of issue with drawing curves with a lot of points? Should the points perhaps be positioned exactly on pixels? I'm sure some of you have worked on something very similar before, so any suggestions? While you're at it, do you have any suggestions for graphing functions with asymptotes? e.g. 1/x^2 P.S. I'm not looking for a library that does all this - I want to write it myself.

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  • 2-column table with two foreign keys. Performance/design question.

    - by Emanuel
    Hello everyone! I recently ran into a quite complex problem and after looking around a lot I couldn't find a solution to it. I've found answers to my questions many times before on stackoverflow.com, so I decided to post here. So I'm making a user/group managment system for a web-based project, and I'm storing all related data into a postgreSQL database. This system relies on three tables: USERS GROUPS GROUP_USERS The two first tables simply define all the users and all the groups on the site, and the last table, GROUP_USERS, stores the groups every user is part of. It only has two columns: USER_ID GROUP_ID Since every user can be a member of several groups, I decided to make a separate table for this purpose, rather than storing a comma separated column in the USERS-table. Now, both columns are foreign keys, and I want to make them both primary keys as well, this since each combination of USER_ID and GROUP_ID has to be unique, and if I give them the constraint UNIQUE pgAdmin tells me that each table should have at least one Primary key. But now I am stuck with what seems to be a lot of indexes and relations to a very small table only containing numbers. In the end, I want this table to be as fast as possible, even if containing tens of thousands of rows. Size on disk shouldn't be a problem since its just all numbers anyway, but it feels quite stupid to have a full-sized index refering to a smaller table. Should I stick with my current solution, store comma-separated values in a column in the USERS-table or is there any other solution I should be aware of. PS. I don't want to use an array-column, even if they are supported by postgreSQL. I want to be as generic as possible so I can switch database later on, if necessary. EDIT: I other words, will using a compound primary key and two foreign keys in one table with only two columns have a negative impact on performance rather than the opposite due to the size of the generated index? Thank you!

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  • C++ Macro Arithmetric

    - by anon
    I have to do with Macros (it's macros calling macros; so templates are out of the question). Here's what I want: foo(3, a, b1, c1) --> foo1(a, b1, c1); foo(5, a, b1, c1, b2, c2) -> foo2(a, b1, c1, b2, c2); foo(7, a, b1, c1, b2, c2, b3, c3) -> foo3(a, b1, c1, b2, c2, b3, c3); So basically, what I want is to be able to execute the "function" n - (n-1)/2 at macro expansion time. Is this possible? Thanks! [PS, if you dislike my questions; I support your right to downvote; my worst question so far is only -17, so maybe we can break that record; however, please let me know why my question is technically invalid.] Thanks EDIT: Foo takes a variable # of arguments, of the form: foo(N, a1, b1, a2, b2, ... a_N, b_N) -> foo##N(a1, b1, a2, b2, ... a_N, b_N);

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  • Expose webservice directly to webclients or keep a thin server-side script layer in between?

    - by max
    Hi, I'm developing a REST webservice (Java, Jersey). The people I'm doing this for want to directly access the webservice via Javascript. Some instinct tells me this is not a good idea, but I cannot really explain that instinct. My natural approach would have been to have the webservice do the real logic and database access, but also have some (relatively thin) server-side script layer (e.g. in PHP). Clients would talk to the PHP layer which in turn would talk to the webservice. (The webservice would be pretty local to the apache/PHP server and implicitly trust calls from the script layer. The script layer would take care of session management.) (Btw, I am not talking about just hiding the webservice behind an Apache which simply redirects calls.) But as I find myself at a lack of words/arguments to explain my instinct, I wonder whether my instinct is right - note that while I have been developing all kinds of software in all kinds of languages and frameworks for like 17 years, this is the first time I develop a webservice. So my question is basically: what are your opinions? Are there any standard setups? Is my instinct totally wrong? Or partially? ;P Many thanks, Max PS: I might add a few bits of information about the planned usage of the whole application: will be accessed by different kinds of users, partly general public, partly privileged thus, all major OS/browser combinations can be expected as clients however, writing the client is not my responsibility will potentially have very high load/traffic logic of webservice will later be massively expanded for another product which is basically a superset of the functionality of the current project there is a significant likelihood that at some point an API should be exposed which can be used by 3rd party developers - obviously, with some restrictions at some point, the public view of the product should become accessible via smartphones, too (in other words, maybe a customized version of the site to adapt to the smaller display and different input methods)

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  • (HTML) PNG on top of another PNG - possible to eliminate full transparency?

    - by MHTri
    I'd like to put a logo png onto of another coloured png. They both have transparent backgrounds. When I try this the images blend together. Curiously, in Photoshop the logo retains its opaque-ness - I put colours on the layers underneath it, another image, etc etc, the logo is still opaque. I'd like to do it this way so I can rotate the background images. How do I fix this? [edit]I've cooked up an example image: http://i.imgur.com/XtoGn.png The left is what I want to happen, the right is what happens on all browsers (I know the background isn't transparent but bear with me - they're both transparent pngs, with the background having a gradient layer mask). I've put the images like this <div> <img id="backgroundImg" style="position: absolute; top: 0;" src="/Images/background.png" /> <img id="logoImg" src="/Images/logo.png" /> </div> I'm not entirely sure what blending mode I'm using in PS.

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  • When is it possible to override top-level bindings in (R7RS) scheme?

    - by Marc
    I have read the current draft of the forthcoming R7RS scheme standard (small language), but I don't understand under which conditions it is not an error to redefine top-level bindings. I guess that it is possible to define or set! a binding that has been introduced at the top-level of a program a second time. But what about imported bindings from an external library? Is it possible to override these bindings by the standard? On page 26/27 of the report, it says: The top level of a program may also include import declarations. In a library declaration, it is an error to import the same identifier more than once with different bindings, or to redefine or mutate an imported binding with define, define-syntax or set!. However, a REPL should permit these actions. Does it mean that redefining is only an error when it does happen in libraries for imported bindings? I understand that it prohibits optimisations by compilers if the compiler does not know whether, say + still means the built-in addition or is any other user-specified error. But from this perspective, it does not make sense to restrict forbidding to rebind on the library level, when it would also make sense (at least) for imported bindings in programs. P.S.: As this is all about the environment of a scheme program: am I right in saying that environments are not first class citizens because one cannot get hold of the current environment? (Which, in turn, allows a compiled program to forget about the chosen names of the bindings.)

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