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• Do you feel underappreciated or resent the geek/nerd stigma?

  - by dotnetdev

  At work we have a piece of A4 paper with the number of everyone in the office. The structure of this document is laid out in rectangles, by department. I work for the department that does all the technical stuff. That includes support—bear in mind that the support staff isn't educated in IT but just has experience in PC maintenance and providing support to a system we resell but don't have source code access to, project manager, team leader, a network administrator, a product manager, and me, a programmer. Anyway, on this paper, we are labelled as nerds and geeks. I did take a little offence to this, as much as it is light hearted (but annoying and old) humour. I have a vivid image that a geek is someone who doesn't go out but codes all day. I code all day at home and at work (when I have something to code...), but I keep balance by going out. I don't know why it is only people who work with computers that get such a stigma. No other profession really gets the same stigma—skilled, technical, or whatever. An account manager (and this is hardly a skilled job) says, "Perhaps [MY NAME HERE] could write some geeky code tomorrow to add this functionality to the website." It is funny how I get such an unfair stigma but I am so pivotal. In fact, if it wasn't for me, the company would have nothing to sell so the account managers would be redundant! I make systems, they get sold, and this is what pays the wages. It's funny how the account managers get a commission for how many systems they sell, or manage to make clients resubscribe to. Yet I built the thing in the first place! On top of that, my brother says all I do is type stuff on a keyboard all day. Surely if I did, I'd be typing at my normal typing speed of 100wpm+ as if I am writing a blog entry. Instead, I plan as I code along on the fly if commercial pressures and time prohibit proper planning. I never type as if I'm writing normal English. There is more to our jobs than just typing code. And my brother is a pipe fitter with no formal qualifications in his name. I could easily, and perhaps more justifiably, say he just manipulates a spanner or something. Does you feel underappreciated or that a geek/nerd stigma is undeserved or unfair?

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• Question about design (inheritance, polymorphism)

  - by Dan

  Hi, I have a question about a problem I'm struggling with. Hope you can bear with me. Imagine I have an Object class representing the base class of a hierarchy of physical objects. Later I inherit from it to create an Object1D, Object2D and Object3D classes. Each of these derived classes will have some specific methods and attributes. For example, the 3d object might have functionality to download a 3d model to be used by a renderer. So I'd have something like this: class Object {}; class Object1D : public Object { Point mPos; }; class Object2D : public Object { ... }; class Object3D : public Object { Model mModel; }; Now I'd have a separate class called Renderer, which simply takes an Object as argument and well, renders it :-) In a similar way, I'd like to support different kinds of renderers. For instance, I could have a default one that every object could rely on, and then provide other specific renderers for some kind of objects: class Renderer {}; // Default one class Renderer3D : public Renderer {}; And here comes my problem. A renderer class needs to get an Object as an argument, for example in the constructor in order to retrieve whatever data it needs to render the object. So far so good. But a Renderer3D would need to get an Object3D argument, in order to get not only the basic attributes but also the specific attributes of a 3d object. Constructors would look like this: CRenderer(Object& object); CRenderer3D(Object3D& object); Now how do I specify this in a generic way? Or better yet, is there a better way to design this? I know I could rely on RTTI or similar but I'd like to avoid this if possible as I feel there is probably a better way to deal with this. Thanks in advance!

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• Want to show <embed> and <object> tags from YUI editor as a text rather then a video.

  - by user208678

  I am using YUI rich text editor on my website (php/mysql), so that a user may enter textual matter/articles through it. But if a user copies and paste some embed code in the textarea, from any video sites like youtube, it should get saved as a text block and not as a playing video when showing the text content on the browser. Now YUI automatically converts the characters into html entities which ever is needed. Please note that if I put a new line in the yui editor (by pressing "Enter" key), it will be converted into a "<br>" tag in the background and this will not get html entity encoded when passing the value to my backend PHP script. But If I copy and paste any embed tag or for that reason any valid html tags in the textarea, it will be html entity encoded by YUI. Now to support UTF-8 characters, I am using a function (DBVarConv) in my php script before saving it into my database. The code for the function is given below function DBVarConv($var,$isEncoded = false) { if($isEncoded) return addslashes(htmlentities($var, ENT_QUOTES, 'UTF-8', false)); else return htmlentities ($var, ENT_QUOTES, 'UTF-8', false); } $myeditorData = DBVarConv($myeditorData, true); // Save $myeditorData in database. While showing the data in the browser, I am using another function called "smart_html_entity_decode". The code is given below. function smart_html_entity_decode($text, $isAddslashesUsed = false) { if($isAddslashesUsed) $tmp = stripslashes(html_entity_decode($text, ENT_QUOTES, 'UTF-8')); else $tmp = html_entity_decode($text, ENT_QUOTES, 'UTF-8'); if ($tmp == $text) return $tmp; return smart_html_entity_decode($tmp, $isAddslashesUsed); } // Get $myData from database $myData=smart_html_entity_decode($myData, true); echo $myData; The problem is that in doing so, it is also decoding the embed and object tags from their html encoded entities and as a result my obejct tags are shown as a video and not as a simple text. Try using the text editor at tumblr.com. If you paste an embed code in the editor, it will be shown as a text block not as a video. I am trying to build the same functionality on my website with UTF-8 support. Any help will be highly appreciated.

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• Are there programs that iteratively write new programs?

  - by chris

  For about a year I have been thinking about writing a program that writes programs. This would primarily be a playful exercise that might teach me some new concepts. My inspiration came from negentropy and the ability for order to emerge from chaos and new chaos to arise out of order in infinite succession. To be more specific, the program would start by writing a short random string. If the string compiles the programs will log it for later comparison. If the string does not compile the program will try to rewrite it until it does compile. As more strings (mini 'useless' programs) are logged they can be parsed for similarities and used to generate a grammar. This grammar can then be drawn on to write more strings that have a higher probability of compilation than purely random strings. This is obviously more than a little silly, but I thought it would be fun to try and grow a program like this. And as a byproduct I get a bunch of unique programs that I can visualize and call art. I'll probably write this in Ruby due to its simple syntax and dynamic compilation and then I will visualize in processing using ruby-processing. What I would like to know is: Is there a name for this type of programming? What currently exists in this field? Who are the primary contributors? BONUS! - In what ways can I procedurally assign value to output programs beyond compiles(y/n)? I may want to extend the functionality of this program to generate a program based on parameters, but I want the program to define those parameters through running the programs that compile and assigning meaning to the programs output. This question is probably more involved than reasonable for a bonus, but if you can think of a simple way to get something like this done in less than 23 lines or one hyperlink, please toss it into your response. I know that this is not quite meta-programming and from the little I know of AI and generative algorithms they are usually more goal oriented than what I am thinking. What would be optimal is a program that continually rewrites and improves itself so I don't have to ^_^

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• how to implement a "soft barrier" in multithreaded c++

  - by Jason

  I have some multithreaded c++ code with the following structure: do_thread_specific_work(); update_shared_variables(); //checkpoint A do_thread_specific_work_not_modifying_shared_variables(); //checkpoint B do_thread_specific_work_requiring_all_threads_have_updated_shared_variables(); What follows checkpoint B is work that could have started if all threads have reached only checkpoint A, hence my notion of a "soft barrier". Typically multithreading libraries only provide "hard barriers" in which all threads must reach some point before any can continue. Obviously a hard barrier could be used at checkpoint B. Using a soft barrier can lead to better execution time, especially since the work between checkpoints A and B may not be load-balanced between the threads (i.e. 1 slow thread who has reached checkpoint A but not B could be causing all the others to wait at the barrier just before checkpoint B). I've tried using atomics to synchronize things and I know with 100% certainty that is it NOT guaranteed to work. For example using openmp syntax, before the parallel section start with: shared_thread_counter = num_threads; //known at compile time #pragma omp flush Then at checkpoint A: #pragma omp atomic shared_thread_counter--; Then at checkpoint B (using polling): #pragma omp flush while (shared_thread_counter > 0) { usleep(1); //can be removed, but better to limit memory bandwidth #pragma omp flush } I've designed some experiments in which I use an atomic to indicate that some operation before it is finished. The experiment would work with 2 threads most of the time but consistently fail when I have lots of threads (like 20 or 30). I suspect this is because of the caching structure of modern CPUs. Even if one thread updates some other value before doing the atomic decrement, it is not guaranteed to be read by another thread in that order. Consider the case when the other value is a cache miss and the atomic decrement is a cache hit. So back to my question, how to CORRECTLY implement this "soft barrier"? Is there any built-in feature that guarantees such functionality? I'd prefer openmp but I'm familiar with most of the other common multithreading libraries. As a workaround right now, I'm using a hard barrier at checkpoint B and I've restructured my code to make the work between checkpoint A and B automatically load-balancing between the threads (which has been rather difficult at times). Thanks for any advice/insight :)

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• Dynamic data-entry value store

  - by simendsjo

  I'm creating a data-entry application where users are allowed to create the entry schema. My first version of this just created a single table per entry schema with each entry spanning a single or multiple columns (for complex types) with the appropriate data type. This allowed for "fast" querying (on small datasets as I didn't index all columns) and simple synchronization where the data-entry was distributed on several databases. I'm not quite happy with this solution though; the only positive thing is the simplicity... I can only store a fixed number of columns. I need to create indexes on all columns. I need to recreate the table on schema changes. Some of my key design criterias are: Very fast querying (Using a simple domain specific query language) Writes doesn't have to be fast Many concurrent users Schemas will change often Schemas might contain many thousand columns The data-entries might be distributed and needs syncronization. Preferable MySQL and SQLite - Databases like DB2 and Oracle is out of the question. Using .Net/Mono I've been thinking of a couple of possible designs, but none of them seems like a good choice. Solution 1: Union like table containing a Type column and one nullable column per type. This avoids joins, but will definitly use a lot of space. Solution 2: Key/value store. All values are stored as string and converted when needed. Also use a lot of space, and of course, I hate having to convert everything to string. Solution 3: Use an xml database or store values as xml. Without any experience I would think this is quite slow (at least for the relational model unless there is some very good xpath support). I also would like to avoid an xml database as other parts of the application fits better as a relational model, and being able to join the data is helpful. I cannot help to think that someone has solved (some of) this already, but I'm unable to find anything. Not quite sure what to search for either... I know market research is doing something like this for their questionnaires, but there are few open source implementations, and the ones I've found doesn't quite fit the bill. PSPP has much of the logic I'm thinking of; primitive column types, many columns, many rows, fast querying and merging. Too bad it doesn't work against a database.. And of course... I don't need 99% of the provided functionality, but a lot of stuff not included. I'm not sure this is the right place to ask such a design related question, but I hope someone here has some tips, know of any existing work, or can point me to a better place to ask such a question. Thanks in advance!

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• Move options between multiple dropdown lists

  - by Martha

  We currently have a form with the standard multi-select functionality of "here are the available options, here are the selected options, here are some buttons to move stuff back and forth." However, the client now wants the ability to not just select certain items, but to also categorize them. For example, given a list of books, they want to not just select the ones they own, but also the ones they've read, the ones they would like to read, and the ones they've heard about. (All examples fictional.) Thankfully, a selected item can only be in one category at a time. I can find many examples of moving items between listboxes, but not a single one for moving items between multiple listboxes. To add to the complication, the form needs to have two sets of list+categories, e.g. a list of movies that need to be categorized in addition to the aforementioned books. An additional problem is that sorting between lists is all well and good in the javascript-enabled world, but I can't really think of a good fallback interface for, say, mobile browsers. Maybe a pseudo-listbox with radio buttons next to each item? The master list of items will in general be very long - over 100 items, certainly, possibly many more. Any given category will most likely contain one or two selected items, but the possibility exists for a category to have dozens of selected items, or zero selected items. As far as OS and stuff, the site is in classic asp (quit snickering!), the server-side code is VBScript, and so far we've avoided the various Javascript libraries by the simple expedient of almost never using client-side scripting. This one form for this one client is currently the big exception. Give 'em an inch and they want a mile... Oh, and I have to add: I suck at Javascript, or really at any C-descendant language. Curly braces give me hives. I'd really, really like something I can just copy & paste into my page, maybe tweak some variable names, and never look at it again. A girl can dream, can't she? :)

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• Why does extend() engage in bizarre behaviour when passed the same list twice?

  - by intuited

  I'm pretty confused by one of the subtleties of the vimscript extend() function. If you use it to extend a list with another list, it does pretty much what you'd expect, which is to insert the second list into the first list at the index given by the third parameter: let list1 = [1,2,3,4,5,6] | echo extend(list1,[1,2,3,4,5,6],5) " [1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 6, 6] However if you give it the same list twice it starts tripping out a bit. let list1 = [1,2,3,4,5,6] | echo extend(list1,list1,0) " [1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6] let list1 = [1,2,3,4,5,6] | echo extend(list1,list1,1) " [1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6] let list1 = [1,2,3,4,5,6] | echo extend(list1,list1,2) " [1, 2, 1, 2, 1, 2, 1, 2, 3, 4, 5, 6] let list1 = [1,2,3,4,5,6] | echo extend(list1,list1,3) " [1, 2, 3, 1, 2, 3, 1, 2, 3, 4, 5, 6] let list1 = [1,2,3,4,5,6] | echo extend(list1,list1,4) " [1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 5, 6] let list1 = [1,2,3,4,5,6] | echo extend(list1,list1,5) " [1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 6] let list1 = [1,2,3,4,5,6] | echo extend(list1,list1,6) " [1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6] Extra-confusingly, this behaviour applies when the list is referenced with two different variables: let list1 = [1,2,3,4,5,6] | let list2 = list1 | echo extend(list1,list2,4) " [1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 5, 6] This is totally bizarre to me. I can't fathom a use for this functionality, and it seems like it would be really easy to invoke it by accident when you just wanted to insert one list into another and didn't realize that the variables were referencing the same array. The documentation says the following: If they are |Lists|: Append {expr2} to {expr1}. If {expr3} is given insert the items of {expr2} before item {expr3} in {expr1}. When {expr3} is zero insert before the first item. When {expr3} is equal to len({expr1}) then {expr2} is appended. Examples: :echo sort(extend(mylist, [7, 5])) :call extend(mylist, [2, 3], 1) When {expr1} is the same List as {expr2} then the number of items copied is equal to the original length of the List. E.g., when {expr3} is 1 you get N new copies of the first item (where N is the original length of the List). Does this make sense in a way that I'm not getting, or is it just an eccentricity?

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• should I ever put a major version number into a C#/Java namespace?

  - by Andrew Patterson

  I am designing a set of 'service' layer objects (data objects and interface definitions) for a WCF web service (that will be consumed by third party clients i.e. not in-house, so outside my direct control). I know that I am not going to get the interface definition exactly right - and am wanting to prepare for the time when I know that I will have to introduce a breaking set of new data objects. However, the reality of the world I am in is that I will also need to run my first version simultaneously for quite a while. The first version of my service will have URL of http://host/app/v1service.svc and when the times comes by new version will live at http://host/app/v2service.svc However, when it comes to the data objects and interfaces, I am toying with putting the 'major' version of the interface number into the actual namespace of the classes. namespace Company.Product.V1 { [DataContract(Namespace = "company-product-v1")] public class Widget { [DataMember] string widgetName; } public interface IFunction { Widget GetWidgetData(int code); } } When the time comes for a fundamental change to the service, I will introduce some classes like namespace Company.Product.V2 { [DataContract(Namespace = "company-product-v2")] public class Widget { [DataMember] int widgetCode; [DataMember] int widgetExpiry; } public interface IFunction { Widget GetWidgetData(int code); } } The advantages as I see it are that I will be able to have a single set of code serving both interface versions, sharing functionality where possible. This is because I will be able to reference both interface versions as a distinct set of C# objects. Similarly, clients may use both interface versions simultaneously, perhaps using V1.Widget in some legacy code whilst new bits move on to V2.Widget. Can anyone tell why this is a stupid idea? I have a nagging feeling that this is a bit smelly.. notes: I am obviously not proposing every single new version of the service would be in a new namespace. Presumably I will do as many non-breaking interface changes as possible, but I know that I will hit a point where all the data modelling will probably need a significant rewrite. I understand assembly versioning etc but I think this question is tangential to that type of versioning. But I could be wrong.

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• Android - Transforming widgets within transformed widgets and the resulting usability issues.

  - by Ben Rose

  Hello. I'm new to Android application development and I'm currently experimenting with various UI ideas. In the image below, you can see a vertically scrolling list of horizontally scrolling galleries (and also textviews as you can see). I'm also doing some matrix and camera transformations which I will come to in a minute. For the background of the list elements, I use green. Blue is the background of the galleries, and red is the background for the images. These are just for my benefit of learning. The galleries being used are extended classes where I overrode the drawChild method to perform a canvas scale operation in order for the image closest to the center (width) to be larger than the others. The list view going vertically, I overrode the drawChild method and used the camera rotations from lack of depth dimension in the canvas functionality. The items in the list are scaled down and rotated relative to their position's proximity to the center (height). I understood that scrolling and clicking would not necessarily follow along with the image transforms, but it appears as though the parent Gallery class's drawing is constrained to the original coordinates as well (see photo below). I would love to hear any insight any of you have regarding how I can change the coordinates of the galleries in what is rendered via gallery scroll and the touch responsiveness of said gallery. Images in the gallery are not same dimensions, so don't let that throw you in looking at the image below Thanks in advance! Ben link to image (could not embed) -- Update: I was using my test application UI and noticed that when I got the UI to the point of the linked image and then I touched the top portion of the next row in the list, the gallery updated to display the proper representation. So, I added a call to clearFocus() in the drawChild method and that resulted in more accurate drawing. It does seem a tad slower, and since I'm on the Incredible, I'm worried it is a bloated solution. In any event, I would still appreciate any thoughts you have regarding the best way to have the views display properly and how to translate the touch events in the gallery's new displayed area to its touchable coordinates so that scrolling on the actual images works when the gallery has moved. Thanks!

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• LINQ Query Returning Multiple Copies Of First Result

  - by Mike G

  I'm trying to figure out why a simple query in LINQ is returning odd results. I have a view defined in the database. It basically brings together several other tables and does some data munging. It really isn't anything special except for the fact that it deals with a large data set and can be a bit slow. I want to query this view based on a long. Two sample queries below show different queries to this view. var la = Runtime.OmsEntityContext.Positions.Where(p => p.AccountNumber == 12345678).ToList(); var deDa = Runtime.OmsEntityContext.Positions.Where(p => p.AccountNumber == 12345678).Select(p => new { p.AccountNumber, p.SecurityNumber, p.CUSIP }).ToList(); The first one should hand back a List. The second one will be a list of anonymous objects. When I do these queries in entities framework the first one will hand me back a list of results where they're all exactly the same. The second query will hand me back data where the account number is the one that I queried and the other values differ. This seems to do this on a per account number basis, ie if I were to query for one account number or another all the Position objects for one account would have the same value (the first one in the list of Positions for that account) and the second account would have a set of Position objects that all had the same value (again, the first one in it's list of Position objects). I can write SQL that is in effect the same as either of the two EF queries. They both come back with results (say four) that show the correct data, one account number with different securities numbers. Why does this happen??? Is there something that I could be doing wrong so that if I had four results for the first query above that the first record's data also appears in the 2-4th's objects??? I cannot fathom what would/could be causing this. I've searched Google for all kinds of keywords and haven't seen anyone with this issue. We partial class out the Positions class for added functionality (smart object) and some smart properties. There are even some constructors that provide some view model type support. None of this is invoked in the request (I'm 99% sure of this). However, we do this same pattern all over the app. The only thing I can think of is that the mapping in the EDMX is screwy. Is there a way that this would happen if the "primary keys" in the EDMX were not in fact unique given the way the view is constructed? I'm thinking that the dev who imported this model into the EDMX let the designer auto select what would be unique. Any help would give a haggered dev some hope!

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• help me "dry" out this .net XML serialization code

  - by Sarah Vessels

  I have a base collection class and a child collection class, each of which are serializable. In a test, I discovered that simply having the child class's ReadXml method call base.ReadXml resulted in an InvalidCastException later on. First, here's the class structure: Base Class // Collection of Row objects [Serializable] [XmlRoot("Rows")] public class Rows : IList<Row>, ICollection<Row>, IEnumerable<Row>, IEquatable<Rows>, IXmlSerializable { public Collection<Row> Collection { get; protected set; } public void ReadXml(XmlReader reader) { reader.ReadToFollowing(XmlNodeName); do { using (XmlReader rowReader = reader.ReadSubtree()) { var row = new Row(); row.ReadXml(rowReader); Collection.Add(row); } } while (reader.ReadToNextSibling(XmlNodeName)); } } Derived Class // Acts as a collection of SpecificRow objects, which inherit from Row. Uses the same // Collection<Row> that Rows defines which is fine since SpecificRow : Row. [Serializable] [XmlRoot("MySpecificRowList")] public class SpecificRows : Rows, IXmlSerializable { public new void ReadXml(XmlReader reader) { // Trying to just do base.ReadXml(reader) causes a cast exception later reader.ReadToFollowing(XmlNodeName); do { using (XmlReader rowReader = reader.ReadSubtree()) { var row = new SpecificRow(); row.ReadXml(rowReader); Collection.Add(row); } } while (reader.ReadToNextSibling(XmlNodeName)); } public new Row this[int index] { // The cast in this getter is what causes InvalidCastException if I try // to call base.ReadXml from this class's ReadXml get { return (Row)Collection[index]; } set { Collection[index] = value; } } } And here's the code that causes a runtime InvalidCastException if I do not use the version of ReadXml shown in SpecificRows above (i.e., I get the exception if I just call base.ReadXml from within SpecificRows.ReadXml): TextReader reader = new StringReader(serializedResultStr); SpecificRows deserializedResults = (SpecificRows)xs.Deserialize(reader); SpecificRow = deserializedResults[0]; // this throws InvalidCastException So, the code above all compiles and runs exception-free, but it bugs me that Rows.ReadXml and SpecificRows.ReadXml are essentially the same code. The value of XmlNodeName and the new Row()/new SpecificRow() are the differences. How would you suggest I extract out all the common functionality of both versions of ReadXml? Would it be silly to create some generic class just for one method? Sorry for the lengthy code samples, I just wanted to provide the reason I can't simply call base.ReadXml from within SpecificRows.

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• Selecting one row when working with typed datasets.

  - by Wodzu

  I have a typed dataset in my project. I would like to populate a datatable with only one row instead of all rows. The selected row must be based on the primary key column. I know I could modify the designer code to achive this functionality however if I change the code in the designer I risk that this code will be deleted when I update my datased via designer in the future. So I wanted to alter the SelectCommand not in the designer but just before firing up MyTypedTableAdapter.Fill method. The strange thing is that the designer does not create a SelectCommand! It creates all other commands but not this one. If it would create SelectCommand I could alter it in this way: this.operatorzyTableAdapter.Adapter.SelectCommand.CommandText += " WHERE MyColumn = 1"; It is far from perfection but atleast I would not have to modify the designer's work. unfortunately as I said earlier the SelectCommand is not created. Instead designer creates something like this: [global::System.Diagnostics.DebuggerNonUserCodeAttribute()] private void InitCommandCollection() { this._commandCollection = new global::System.Data.SqlClient.SqlCommand[1]; this._commandCollection[0] = new global::System.Data.SqlClient.SqlCommand(); this._commandCollection[0].Connection = this.Connection; this._commandCollection[0].CommandText = "SELECT Ope_OpeID, Ope_Kod, Ope_Haslo, Ope_Imie, Ope_Nazwisko FROM dbo.Operatorzy"; this._commandCollection[0].CommandType = global::System.Data.CommandType.Text; } It doesn't make sense in my opinion. Why to create UpdateCommand, InsertCommand and DeleteCommand but do not create SelectCommand? I could bear with this but this._commandCollection is private so I cannot acces it outside of the class code. I don't know how to get into this collection without changing the designer's code. The idea which I have is to expose the collection via partial class definition. However I want to introduce many typed datasets and I really don't want to create partial class definition for each of them. Please note that I am using .NET 3.5. I've found this article about accessing private properties but it concerns .NET 4.0 Thanks for your time.

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• Runge-Kutta Method with adaptive step

  - by infoholic_anonymous

  I am implementing Runge-Kutta method with adaptive step in matlab. I get different results as compared to matlab's own ode45 and my own implementation of Runge-Kutta method with fixed step. What am I doing wrong in my code? Is it possible? function [ result ] = rk4_modh( f, int, init, h, h_min ) % % f - function handle % int - interval - pair (x_min, x_max) % init - initial conditions - pair (y1(0),y2(0)) % h_min - lower limit for h (step length) % h - initial step length % x - independent variable ( for example time ) % y - dependent variable - vertical vector - in our case ( y1, y2 ) function [ k1, k2, k3, k4, ka, y ] = iteration( f, h, x, y ) % core functionality performed within loop k1 = h * f(x,y); k2 = h * f(x+h/2, y+k1/2); k3 = h * f(x+h/2, y+k2/2); k4 = h * f(x+h, y+k3); ka = (k1 + 2*k2 + 2*k3 + k4)/6; y = y + ka; end % constants % relative error eW = 1e-10; % absolute error eB = 1e-10; s = 0.9; b = 5; % initialization i = 1; x = int(1); y = init; while true hy = y; hx = x; %algorithm [ k1, k2, k3, k4, ka, y ] = iteration( f, h, x, y ); % error estimation for j=1:2 [ hk1, hk2, hk3, hk4, hka, hy ] = iteration( f, h/2, hx, hy ); hx = hx + h/2; end err(:,i) = abs(hy - y); % step adjustment e = abs( hy ) * eW + eB; a = min( e ./ err(:,i) )^(0.2); mul = a * s; if mul >= 1 % step length admitted keepH(i) = h; k(:,:,i) = [ k1, k2, k3, k4, ka ]; previous(i,:) = [ x+h, y' ]; %' i = i + 1; if floor( x + h + eB ) == int(2) break; else h = min( [mul*h, b*h, int(2)-x] ); x = x + keepH(i-1); end else % step length requires further adjustments h = mul * h; if ( h < h_min ) error('Computation with given precision impossible'); end end end result = struct( 'val', previous, 'k', k, 'err', err, 'h', keepH ); end The function in question is: function [ res ] = fun( x, y ) % res(1) = y(2) + y(1) * ( 0.9 - y(1)^2 - y(2)^2 ); res(2) = -y(1) + y(2) * ( 0.9 - y(1)^2 - y(2)^2 ); res = res'; %' end The call is: res = rk4( @fun, [0,20], [0.001; 0.001], 0.008 ); The resulting plot for x1 : The result of ode45( @fun, [0, 20], [0.001, 0.001] ) is:

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• Autocomplete server-side implementation

  - by toluju

  What is a fast and efficient way to implement the server-side component for an autocomplete feature in an html input box? I am writing a service to autocomplete user queries in our web interface's main search box, and the completions are displayed in an ajax-powered dropdown. The data we are running queries against is simply a large table of concepts our system knows about, which matches roughly with the set of wikipedia page titles. For this service obviously speed is of utmost importance, as responsiveness of the web page is important to the user experience. The current implementation simply loads all concepts into memory in a sorted set, and performs a simple log(n) lookup on a user keystroke. The tailset is then used to provide additional matches beyond the closest match. The problem with this solution is that it does not scale. It currently is running up against the VM heap space limit (I've set -Xmx2g, which is about the most we can push on our 32 bit machines), and this prevents us from expanding our concept table or adding more functionality. Switching to 64-bit VMs on machines with more memory isn't an immediate option. I've been hesitant to start working on a disk-based solution as I am concerned that disk seek time will kill performance. Are there possible solutions that will let me scale better, either entirely in memory or with some fast disk-backed implementations? Edits: @Gandalf: For our use case it is important the the autocompletion is comprehensive and isn't just extra help for the user. As for what we are completing, it is a list of concept-type pairs. For example, possible entries are [("Microsoft", "Software Company"), ("Jeff Atwood", "Programmer"), ("StackOverflow.com", "Website")]. We are using Lucene for the full search once a user selects an item from the autocomplete list, but I am not yet sure Lucene would work well for the autocomplete itself. @Glen: No databases are being used here. When I'm talking about a table I just mean the structured representation of my data. @Jason Day: My original implementation to this problem was to use a Trie, but the memory bloat with that was actually worse than the sorted set due to needing a large number of object references. I'll read on the ternary search trees to see if it could be of use.

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• How to properly downcast in C# with a SWIG generated interface?

  - by JG

  I've got a very large and mature C++ code base that I'm trying to use SWIG on to generate a C# interface for. I cannot change the actual C++ code itself but we can use whatever SWIG offers in the way of extending/updating it. I'm facing an issue where a function C++ is written as such: A* SomeClass::next(A*) The caller might do something like: A* acurr = 0; while( (acurr = sc->next(acurr)) != 0 ){ if( acurr isoftype B ){ B* b = (B*)a; ...do some stuff with b.. } elseif( acurr isoftype C ) ... } Essentially, iterating through a container elements that depending on their true type, do something different. The SWIG generated C# layer for the "next" function unfortunately does the following: return new A(); So the calling code in C# land cannot determine if the returned object is actually a derived class or not, it actually appears to always be the base class (which does make sense). I've come across several solutions: Use the %extend SWIG keyword to add a method on an object and ultimately call dynamic_cast. The downside to this approach, as I see it, is that this requires you to know the inheritance hierarchy. In my case it is rather huge and I see this is as a maintenance issue. Use the %factory keyword to supply the method and the derived types and have SWIG automatically generate the dynamic_cast code. This appears to be a better solution that the first, however upon a deeper look it still requires you to hunt down all the methods and all the possible derived types it could return. Again, a huge maintenance issue. I wish I had a doc link for this but I can't find one. I found out about this functionality by looking through the example code that comes with SWIG. Create a C# method to create an instance of the derived object and transfer the cPtr to the new instance. While I consider this clumsy, it does work. See an example below. public static object castTo(object fromObj, Type toType) { object retval = null; BaseClass fromObj2 = fromObj as BaseClass; HandleRef hr = BaseClass.getCPtr(fromObj2); IntPtr cPtr = hr.Handle; object toObj = Activator.CreateInstance(toType, cPtr, false); // make sure it actually is what we think it is if (fromObj.GetType().IsInstanceOfType(toObj)) { return toObj; } return retval; } Are these really the options? And if I'm not willing to dig through all the existing functions and class derivations, then I'm left with #3? Any help would be appreciated.

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• many-to-many performance concerns with fluent nhibernate.

  - by Ciel

  I have a situation where I have several many-to-many associations. In the upwards of 12 to 15. Reading around I've seen that it's generally believed that many-to-many associations are not 'typical', yet they are the only way I have been able to create the associations appropriate for my case, so I'm not sure how to optimize any further. Here is my basic scenario. class Page { IList<Tag> Tags { get; set; } IList<Modification> Modifications { get; set; } IList<Aspect> Aspects { get; set; } } This is one of my 'core' classes, and coincidentally one of my core tables. Virtually half of the objects in my code can have an IList<Page>, and some of them have IList<T> where T has its own IList<Page>. As you can see, from an object oriented standpoint, this is not really a problem. But from a database standpoint this begins to introduce a lot of junction tables. So far it has worked fine for me, but I am wondering if anyone has any ideas on how I could improve on this structure. I've spent a long time thinking and in order to achieve the appropriate level of association required, I cannot think of any way to improve it. The only thing I have come up with is to make intermediate classes for each object that has an IList<Page>, but that doesn't really do anything that the HasManyToMany does not already do except introduce another class. It does not extend the functionality and, from what I can tell, it does not improve performance. Any thoughts? I am also concerned about Primary Key limits in this scenario. Most everything needs to be able to have these properties, but the Pages cannot be unique to each object, because they are going to be frequently shared and joined between multiple objects. All relationships are one-sided. (That is, a Page has no knowledge of what owns it). Because of this, I also have no Inverse() mapped HasManyToMany collections. Also, I have read the similar question : Usage of ORMs like NHibernate when there are many associations - performance concerns But it really did not answer my concerns.

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• QTreeView memory consumption

  - by Eye of Hell

  Hello. I'm testing QTreeView functionality right now, and i was amazed by one thing. It seems that QTreeView memory consumption depends on items count O_O. This is highly unusual, since model-view containers of such type only keeps track for items being displayed, and rest of items are in the model. I have written a following code with a simple model that holds no data and just reports that it has 10 millions items. With MFC, Windows API or .NET tree / list with such model will take no memory, since it will display only 10-20 visible elements and will request model for more upon scrolling / expanding items. But with Qt, such simple model results in ~300Mb memory consumtion. Increasing number of items will increase memory consumption. Maybe anyone can hint me what i'm doing wrong? :) #include <QtGui/QApplication> #include <QTreeView> #include <QAbstractItemModel> class CModel : public QAbstractItemModel { public: QModelIndex index ( int i_nRow, int i_nCol, const QModelIndex& i_oParent = QModelIndex() ) const { return createIndex( i_nRow, i_nCol, 0 ); } public: QModelIndex parent ( const QModelIndex& i_oInex ) const { return QModelIndex(); } public: int rowCount ( const QModelIndex& i_oParent = QModelIndex() ) const { return i_oParent.isValid() ? 0 : 1000 * 1000 * 10; } public: int columnCount ( const QModelIndex& i_oParent = QModelIndex() ) const { return 1; } public: QVariant data ( const QModelIndex& i_oIndex, int i_nRole = Qt::DisplayRole ) const { return Qt::DisplayRole == i_nRole ? QVariant( "1" ) : QVariant(); } }; int main(int argc, char *argv[]) { QApplication a(argc, argv); QTreeView oWnd; CModel oModel; oWnd.setUniformRowHeights( true ); oWnd.setModel( & oModel ); oWnd.show(); return a.exec(); }

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• Cannot figure out how to take in generic parameters for an Enterprise Framework library sql statemen

  - by KallDrexx

  I have written a specialized class to wrap up the enterprise library database functionality for easier usage. The reasoning for using the Enterprise Library is because my applications commonly connect to both oracle and sql server database systems. My wrapper handles both creating connection strings on the fly, connecting, and executing queries allowing my main code to only have to write a few lines of code to do database stuff and deal with error handling. As an example my ExecuteNonQuery method has the following declaration: /// <summary> /// Executes a query that returns no results (e.g. insert or update statements) /// </summary> /// <param name="sqlQuery"></param> /// <param name="parameters">Hashtable containing all the parameters for the query</param> /// <returns>The total number of records modified, -1 if an error occurred </returns> public int ExecuteNonQuery(string sqlQuery, Hashtable parameters) { // Make sure we are connected to the database if (!IsConnected) { ErrorHandler("Attempted to run a query without being connected to a database.", ErrorSeverity.Critical); return -1; } // Form the command DbCommand dbCommand = _database.GetSqlStringCommand(sqlQuery); // Add all the paramters foreach (string key in parameters.Keys) { if (parameters[key] == null) _database.AddInParameter(dbCommand, key, DbType.Object, null); else _database.AddInParameter(dbCommand, key, DbType.Object, parameters[key].ToString()); } return _database.ExecuteNonQuery(dbCommand); } _database is defined as private Database _database;. Hashtable parameters are created via code similar to p.Add("@param", value);. the issue I am having is that it seems that with enterprise library database framework you must declare the dbType of each parameter. This isn't an issue when you are calling the database code directly when forming the paramters but doesn't work for creating a generic abstraction class such as I have. In order to try and get around that I thought I could just use DbType.Object and figure the DB will figure it out based on the columns the sql is working with. Unfortunately, this is not the case as I get the following error: Implicit conversion from data type sql_variant to varchar is not allowed. Use the CONVERT function to run this query Is there any way to use generic parameters in a wrapper class or am I just going to have to move all my DB code into my main classes?

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• Is it possible to read infinity or NaN values using input streams?

  - by Drise

  I have some input to be read by a input filestream (for example): -365.269511 -0.356123 -Inf 0.000000 When I use std::ifstream mystream; to read from the file to some double d1 = -1, d2 = -1, d3 = -1, d4 = -1; (assume mystream has already been opened and the file is valid), mystream >> d1 >> d2 >> d3 >> d4; mystream is in the fail state. I would expect std::cout << d1 << " " << d2 << " " << d3 << " " << d4 << std::endl; to output -365.269511 -0.356123 -1 -1. I would want it to output -365.269511 -0.356123 -Inf 0 instead. This set of data was output using C++ streams. Why can't I do the reverse process (read in my output)? How can I get the functionality I seek? From MooingDuck: #include <iostream> #include <limits> using namespace std; int main() { double myd = std::numeric_limits<double>::infinity(); cout << myd << '\n'; cin >> myd; cout << cin.good() << ":" << myd << endl; return 0; } Input: inf Output: inf 0:inf See also: http://ideone.com/jVvei Also related to this problem is NaN parsing, even though I do not give examples for it.

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• How do I use a custom #theme function to a fieldset in a drupal module?

  - by Rob Crowell

  I have a module that builds a form that includes a fieldset. Instead of using the <legend> element to render the fieldset title, I want to place this content in a <div> element instead. But I want to change the behavior only for the form returned by my module, so I don't want to place any new functionality into my theme's template.php file. In mymod.module I have defined: // custom rendering function for fieldset elements function theme_mymod_fieldset($element) { return 'test'; } // implement hook_theme function mymod_theme() { return array( 'mymod_fieldset' => array('arguments' => array('element' => NULL)), 'mymod_form' => array('arguments' => array()) ); } // return a form that is based on the 'Basic Account Info' category of the user profile function mymod_form() { // load the user's profile global $user; $account = user_load($user->uid); // load the profile form, and then edit it $form_state = array(); $form = drupal_retrieve_form('user_profile_form', $form_state, $account, 'Basic Account Info'); // set the custom #theme function for this fieldset $form['Basic Account Info']['#theme'] = 'mymod_fieldset'; // more form manipulations // ... return $form; } When my page gets rendered, I expected to see the fieldset representing 'Basic Account Info' to be wholly replaced by my test message 'test'. Instead what happens is that the <fieldset> and <legend> elements are rendered as normal, but with the body of the fieldset replaced by the test message instead, like this: <fieldset> <legend>Basic Account Info</legend> test </fieldset> Why doesn't my #theme function have the chance to replace the entire <fieldset> element? If I wrap a textfield in this function instead, I am able to completely replace the <input> element along with its label. Furthermore, if I provide an override in my site's template.php for theme_fieldset, it works as expected and I am able to completely replace the <fieldset>, so I know it is possible. What's different about providing #theme functions to fieldsets inside a module?

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• plupload not working in wordpress theme files

  - by Kedar B

  This is my code for image upload.... <a id="aaiu-uploader" class="aaiu_button" href="#"><?php _e('*Select Images (mandatory)','wpestate');?></a> <input type="hidden" name="attachid" id="attachid" value="<?php echo $attachid;?>"> <input type="hidden" name="attachthumb" id="attachthumb" value="<? php echo $thumbid;?>"> i want upload functionality more than one time in single page in wordpress.i have add js code for that same as first upload block but its not working. This is js code for image upload.... jQuery(document).ready(function($) { "use strict"; if (typeof(plupload) !== 'undefined') { var uploader = new plupload.Uploader(ajax_vars.plupload); uploader.init(); uploader.bind('FilesAdded', function (up, files) { $.each(files, function (i, file) { // console.log('append'+file.id ); $('#aaiu-upload-imagelist').append( '<div id="' + file.id + '">' + file.name + ' (' + plupload.formatSize(file.size) + ') <b></b>' + '</div>'); }); up.refresh(); // Reposition Flash/Silverlight uploader.start(); }); uploader.bind('UploadProgress', function (up, file) { $('#' + file.id + " b").html(file.percent + "%"); }); // On erro occur uploader.bind('Error', function (up, err) { $('#aaiu-upload-imagelist').append("<div>Error: " + err.code + ", Message: " + err.message + (err.file ? ", File: " + err.file.name : "") + "</div>" ); up.refresh(); // Reposition Flash/Silverlight }); uploader.bind('FileUploaded', function (up, file, response) { var result = $.parseJSON(response.response); // console.log(result); $('#' + file.id).remove(); if (result.success) { $('#profile-image').css('background-image','url("'+result.html+'")'); $('#profile-image').attr('data-profileurl',result.html); $('#profile-image_id').val(result.attach); var all_id=$('#attachid').val(); all_id=all_id+","+result.attach; $('#attachid').val(all_id); $('#imagelist').append('<div class="uploaded_images" data- imageid="'+result.attach+'"><img src="'+result.html+'" alt="thumb" /><i class="fa deleter fa-trash-o"></i> </div>'); delete_binder(); thumb_setter(); } }); $('#aaiu-uploader').click(function (e) { uploader.start(); e.preventDefault(); }); $('#aaiu-uploader2').click(function (e) { uploader.start(); e.preventDefault(); }); } });

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• Move options between multiple lists

  - by Martha

  We currently have a form with the standard multi-select functionality of "here are the available options, here are the selected options, here are some buttons to move stuff back and forth." However, the client now wants the ability to not just select certain items, but to also categorize them. For example, given a list of books, they want to not just select the ones they own, but also the ones they've read, the ones they would like to read, and the ones they've heard about. (All examples fictional.) Thankfully, a selected item can only be in one category at a time. I can find many examples of moving items between listboxes, but not a single one for moving items between multiple listboxes. To add to the complication, the form needs to have two sets of list+categories, e.g. a list of movies that need to be categorized in addition to the aforementioned books. EDIT: Having now actually sat down to try to code the non-javascripty bits, I need to revise my question, because I realized that multiple select lists won't really work from the "how do I inform the server about all this lovely new information" standpoint. So the html code is now a pseudo-listbox, i.e. an unordered list (ul) displayed in a box with a scrollbar, and each list item (<li>) has a set of five radio buttons (unselected/own/read/like/heard). My task is still roughly the same: how to take this one list and make it easy to categorize the items, in such a way that the user can tell at a glance what is in what category. (The pseudo-listbox has some of the same disadvantages as a multi-select listbox, namely it's hard to tell what's selected if the list is long enough to scroll.) The dream solution would be a drag-and-drop type thing, but at this point even buttons would be OK. Another modification (a good one) is that the client has revised the lists, so the longest is now "only" 62 items long (instead of the many hundreds they had before). The categories will still mostly contain zero, one, or two selected items, possibly a couple more if the user was overzealous. As far as OS and stuff, the site is in classic asp (quit snickering!), the server-side code is VBScript, and so far we've avoided the various Javascript libraries by the simple expedient of almost never using client-side scripting. This one form for this one client is currently the big exception. Give 'em an inch and they want a mile... Oh, and I have to add: I suck at Javascript, or really at any C-descendant language. Curly braces give me hives. I'd really, really like something I can just copy & paste into my page, maybe tweak some variable names, and never look at it again. A girl can dream, can't she? :) [existing code deleted because it's largely irrelevant.]

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• How to redirect to a page using a button tag in html?

  - by Vlad Radulescu

  When I Click a button I want to get redirected to a page. The problem is...if I use the normal sintax , the button works fine, but If I apply some css to id by ussing # and .(classes) ,the button it`s not working any more ?! How can I keep my css and functionality at the same time ?! This is my code: <body> <input id="buttonrain" class="classname" type="button" onClick="window.location.href='rain.html'" value="Rain" /> <!--or <a href="rain.html" id="buttonrain" class="classname">Rain</a> still not working--> </body> CSS FILE html { min-width: 100%; min-height: 100%; } body{ width: 1024px; height:600px; background:white; margin:0px; padding:0px 0px; display:block; overflow:hidden; } .classname { -moz-box-shadow:inset 0px 1px 0px 0px #ffffff; -webkit-box-shadow:inset 0px 1px 0px 0px #ffffff; box-shadow:inset 0px 1px 0px 0px #ffffff; background:-webkit-gradient( linear, left top, left bottom, color-stop(0.05, #f0ea3c), color-stop(1, #dfdfdf) ); background:-moz-linear-gradient( center top, #f0ea3c 5%, #dfdfdf 100% ); filter:progid:DXImageTransform.Microsoft.gradient(startColorstr='#f0ea3c', endColorstr='#dfdfdf'); background-color:#f0ea3c; -moz-border-radius:6px; -webkit-border-radius:6px; border-radius:6px; border:1px solid #dcdcdc; display:inline-block; color:#0f000f; font-family:Verdana; font-size:15px; font-weight:bold; padding:18px 9px; text-decoration:none; text-shadow:1px 1px 0px #ffffff; position:relative; bottom:250px; }.classname:active { position:relative; top:1px; } #buttonrain{ left:80px; }

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• iOS: Gesture recogniser for smooth scrolling and flicking a View

  - by AppleDeveloper

  I am building an iPad app where I needed to allow resizing views functionality using divider view provided between two views. This divider view is just a 20px height view between two half screen content views - please refer attached images. When user scrolls this divider view up or down, both content views changes their sizes appropriately. I have extended UIView and implemented this using touchMoved delegate as code given below in touchesMoved delegate. It works fine. The only thing is missing with TouchMoved is you can't flick divider view to top or bottom directly. You have to scroll all the way to top or bottom! To support flicking the view I have tried UIPanGestureRecognizer but I don't see smooth scrolling with it. When I handle split position change in UIGestureRecognizerStateChanged state, just touching divider view flick it to top or bottom. Handling split position change in UIGestureRecognizerStateEnded does the same but I don't see content view resizing with dividerview scrolling! Could someone please tell me how could I achieve both smooth scrolling of divider view with resizing content views(like touchMoved) and flicking the view. Any alternative approach would also fine. Thanks. - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; if (touch) { CGPoint lastPt = [touch previousLocationInView:self]; CGPoint pt = [touch locationInView:self]; float offset = pt.y - lastPt.y; self.parentViewController.splitPosition = self.parentViewController.splitPosition + offset; } } - (void)handlePan:(UIPanGestureRecognizer*)recognizer { CGPoint translation = [recognizer translationInView:recognizer.view]; CGPoint velocity = [recognizer velocityInView:recognizer.view]; if (recognizer.state == UIGestureRecognizerStateBegan) { } else if (recognizer.state == UIGestureRecognizerStateChanged) { // If I change split position here, I don't see smooth scrolling dividerview...it directly jumps to the top or bottom! self.parentViewController.splitPosition = self.parentViewController.splitPosition + translation.y; } else if (recognizer.state == UIGestureRecognizerStateEnded) { // If I change split position here, the same thing happens at end and I don't see my divider view moving with my scrolling and resizing my views. self.parentViewController.splitPosition = self.parentViewController.splitPosition + translation.y; } } Initial screen Increased top view size by scrolling divider view Top view is totally hidden here but I have to scroll divider view all the way to top. I want to flick the divider view so that it directly goes from any position to top

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