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• FIFO implementation

  - by Narek

  While implementing a FIFO I have used the following structure: struct Node { T info_; Node* link_; Node(T info, Node* link=0): info_(info), link_(link) {} }; I think this a well known trick for lots of STL containers (for example for List). Is this a good practice? What it means for compiler when you say that Node has a member with a type of it's pointer? Is this a kind of infinite loop? And finally, if this is a bad practice, how I could implement a better FIFO. EDIT: People, this is all about implemenation. I am enough familiar with STL library, and know a plenty of containers from several libraries. Just I want to discuss with people who can gave a good implementation or a good advice.

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• Php PEAR, Database Abstraction & Factory Methods

  - by pws5068

  I'm interested in learning more about design practices in PHP for Database Abstraction & Factory methods. For background, my site is a special-interest social networking community currently in beta mode. Currently, I've started moving my old code for object retrieval to factory methods. However, I do feel like I'm limiting myself by keeping a lot of SQL table names and structure separated in each function/method. Questions: 1.) Is there a reason to use PEAR (or similar) if I dont anticipate switching databases? 2.) Can PEAR interface with the MySqli prepared statements I currently use? 3.) Will it help me separate table names from each method? (If no, what other design patterns might I want to research?) 4.) Will it slow down my site once I have a significantly large member base?

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• linq-to-sql "an attempt has been made to attach or add an entity that is not new"?

  - by Curtis White

  I've been getting several errors: cannot add an entity with a key that is already in use An attempt has been made to attach or add an entity that is not new, perhaps having been loaded from another datacontext In case 1, this stems from trying to set the key for an entity versus the entity. In case 2, I'm not attaching an entity but I am doing this: MyParent.Child = EntityFromOtherDataContext; I've been using using the pattern of wrap everything with a using datacontext. In my case, I am using this in a web forms scenario, and obviously moving the datacontext object to a class wide member variables solves this. My questions are thus 2 fold: How can I get rid of these errors and not have to structure my program in an odd way or pass the datacontext around while keeping the local-wrap pattern? I assume I could make another hit to the database but that seems very inefficient. Would most people recommend that moving the datacontext to the class wide scope is desirable for web pages?

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• SQL Complicated Group / Join by Category

  - by Mike Silvis

  I currently have a database structure with two important tables. 1) Food Types (Fruit, Vegetables, Meat) 2) Specific Foods (Apple, Oranges, Carrots, Lettuce, Steak, Pork) I am currently trying to build a SQL statement such that I can have the following. Fruit < Apple, Orange Vegetables < Carrots, Lettuce Meat < Steak, Port I have tried using a statement like the following Select * From Food_Type join (Select * From Foods) as Foods on Food_Type.Type_ID = Foods.Type_ID but this returns every Specific Food, while I only want the first 2 per category. So I basically need my subquery to have a limit statement in it so that it finds only the first 2 per category. However if I simply do the following Select * From Food_Type join (Select * From Foods LIMIT 2) as Foods on Food_Type.Type_ID = Foods.Type_ID My statement only returns 2 results total.

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• Track each request to the website using HttpModule

  - by stacker

  I want to save each request to the website. In general I want to include the following information: User IP, The web site url, user-if-exist, date-time. Response time, response success-failed status. Is it reasonable to collect the 1 and 2 in the same action? (like same HttpModule)? Do you know about any existing structure that I can follow that track every request/response-status to the website? The data need to be logged to sql server.

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• Fastest way to calculate summary of database field

  - by Jo-wen

  I have a ms-sql table with the following structure: Name nvarchar; Sign nvarchar; Value int example contents: Test1, 'plus', 5 Test1, 'minus', 3 Test2, 'minus', 1 I would like to have totals per "Name". (add when sign = plus, subtract when sign = minus) result: Test1, 2 Test2, -1 I want to show these results (and update them when a new record is added)... and I'm looking for the fastest solution! [sproc? fast-forward cursor? calculate in .net?]

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• How to force rebase when same changes applied to both branches manually?

  - by Dmitry

  My repository looks like: X - Y- A - B - C - D - E branch:master \ \ \ \ merge master -> release \ \ M --- BCDE --- N branch:release Here "M - BCDE - N" are manually (unfortunately!) applied changes approximately same as separate commits "A - B - C - D - E" (but seems GIT does not know that these changes are the same). I'd like to rebase and get the following structure: X - Y- A - B - C - D - E branch:master \ * branch:release I.e. I want to make branch:release to be exactly the same as branch:master and fork it from the master's HEAD. But when I run "git rebase master" sitting at the branch release, GIT reports about lots of conflicts and refuces rebasing. How could I solve this? Other explaination of this: I'd like to "re-create" branch:release from scratch from master's HEAD. And there are a lot of other people who had already made "git pull" for the branch:release, so I cannot use git reset + git push -f.

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• Recommendations for an in memory database vs thread safe data structures

  - by yx

  TLDR: What are the pros/cons of using an in-memory database vs locks and concurrent data structures? I am currently working on an application that has many (possibly remote) displays that collect live data from multiple data sources and renders them on screen in real time. One of the other developers have suggested the use of an in memory database instead of doing it the standard way our other systems behaves, which is to use concurrent hashmaps, queues, arrays, and other objects to store the graphical objects and handling them safely with locks if necessary. His argument is that the DB will lessen the need to worry about concurrency since it will handle read/write locks automatically, and also the DB will offer an easier way to structure the data into as many tables as we need instead of having create hashmaps of hashmaps of lists, etc and keeping track of it all. I do not have much DB experience myself so I am asking fellow SO users what experiences they have had and what are the pros & cons of inserting the DB into the system?

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• Eclipse Problems View doesn't show Errors

  - by Jack

  [Note: There is another thread about this problem but it did not answer the question.] For one specific project in Eclipse, the problems view does not show errors. It shows warnings but it does not show errors. The other projects do show errors (and everything else). For that problematic project, I can see the red squiggly error line in the files. However, the directory structure does not show an error icon and the error is not populated in the Problems View. Any ideas?

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• List of generic algorithms and data structures

  - by Jake Petroules

  As part of a library project, I want to include a plethora of generic algorithms and data structures. This includes algorithms for searching and sorting, data structures like linked lists and binary trees, path-finding algorithms like A*... the works. Basically, any generic algorithm or data structure you can think of that you think might be useful in such a library, please post or add it to the list. Thanks! (NOTE: Because there is no single right answer I've of course placed this in community wiki... and also, please don't suggest algorithms which are too specialized to be provided by a generic library) The List: Data structures AVL tree B-tree B*-tree B+-tree Binary tree Binary heap Binary search tree Linked lists Singly linked list Doubly linked list Stack Queue Sorting algorithms Binary tree sort Bubble sort Heapsort Insertion sort Merge sort Quicksort Selection sort Searching algorithms

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• Hiding members in a C struct

  - by Marlon

  I've been reading about OOP in C but I never liked how you can't have private data members like you can in C++. But then it came to my mind that you could create 2 structures. One is defined in the header file and the other is defined in the source file. // ========================================= // in somestruct.h typedef struct { int _public_member; } SomeStruct; // ========================================= // in somestruct.cpp #include "somestruct.h" typedef struct { int _public_member; int _private_member; } SomeStructSource; SomeStruct *SomeStruct_Create() { SomeStructSource *p = (SomeStructSource *)malloc(sizeof(SomeStructSource)); p->_private_member = 0xWHATEVER; return (SomeStruct *)p; } From here you can just cast one structure to the other. Is this considered bad practice? Or is it done often? (I think this is done with a lot of the structures when using the Win32 API, but you guys are the experts let me know!)

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• How to deal with routing when developing a custom CMS in Codeigniter

  - by Ashley Ward

  Hi All - I’m a recent user of Codeigniter and am developing a simple backend CMS to manage pages. Based on a URL (in this example I have hidden “index.php”) : mysite.com/pagename I would like the system to detect if there is a value of “pagename” in my database, if there is, I need the system to re-route to a custom controller (eg: Pagemaker) and if there is no record called pagename, just do it’s normal thing (i.e. find a controller called pagename) Currently I have: $route['(:any)'] = "pagemaker/create/$1"; whereby all requests are forwarded to my custom function. However I want to change this structure so that if the page does NOT exist in the db, the traditional codeigniter request process is followed. Can anyone offer any advice about how to complete this? Or any advice about routing custom CMS’s in codeigniter in general?

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• query optimization

  - by Gaurav

  I have a query of the form SELECT uid1,uid2 FROM friend WHERE uid1 IN (SELECT uid2 FROM friend WHERE uid1='.$user_id.') and uid2 IN (SELECT uid2 FROM friend WHERE uid1='.$user_id.') The problem now is that the nested query SELECT uid2 FROM friend WHERE uid1='.$user_id.' returns a very large number of ids(approx. 5000). The table structure of the friend table is uid1(int), uid2(int). This table is used to determine whether two users are linked together as friends. Any workaround? Can I write the query in a different way? Or is there some other way to solve this issue. I'm sure I am not the first person to face such a problem. Any help would be greatly appreciated.

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• CakePHP. How can i make a model test in a table with another primary key?

  - by Marcelo

  I have this table CREATE TABLE myexamples.problems ( id INT, name VARCHAR(45) NULL , pk_id INT AUTO_INCREMENT PRIMARY KEY ); But when I try test a model in cakephp, it fails because the table has two autoincrement attributes. The following query CREATE TABLE `test_suite_problems` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(45) DEFAULT NULL, `pk_id` int(11) NOT NULL AUTO_INCREMENT, PRIMARY KEY (`pk_id`) ) DEFAULT CHARSET=latin1, COLLATE=latin1_swedish_ci, ENGINE=InnoDB; raise this error: "1075: Incorrect table definition; there can be only one auto column and it must be defined as a key" I have in the model class <?php class Problem extends AppModel { var $name = 'Problem'; var $displayField = 'name'; var $primaryKey='problems'; } ?> But I don't know how to make the field ID not having an autoincrement attribute, and I can't change the table structure.

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• InvalidOperationException When XML Serializing Inherited Class

  - by Nick

  I am having an issue serializing a c# class to an XML file that has a base class... here is a simple example: namespace Domain { [Serializable] public class ClassA { public virtual int MyProperty { get; set; } } } namespace Derived { public class ClassA : Domain.ClassA { public override int MyProperty { get { return 1; } set { /* Do Nothing */ } } } } When I attempt to serialize an instance of Derived.ClassA, I receive the following exception: InvalidOperationException(Types 'Domain.ClassA' and 'Derived.ClassA' both use the XML type name 'ClassA', from the namespace ". Use XML attributes to specify a unique XML name and/or namespace for the type.) The problem is that I want to create a single base class that simply defines the structure of the XML file, and then allow anyone else to derive from that class to insert business rules, but that the formatting will come through from the base. Is this possible, and if so, how do I attribute the base class to allow this?

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• Three level database - foreign keys

  - by poke

  I have a three level database with the following structure (simplified to only show the primary keys): Table A: a_id Table B: a_id, b_id Table C: a_id, b_id, c_id So possible values for table C would be something like this: a_id b_id c_id 1 1 1 1 1 2 1 1 3 1 2 1 1 2 2 2 1 1 2 2 1 2 2 2 ... I am now unsure, how foreign keys should be set; or if they should be set for the primary keys at all. My idea was to have a foreign key on table B B.a_id -> A.a_id, and two foreign key on C C.a_id -> A.a_id and ( C.a_id, C.b_id ) -> ( B.a_id, B.b_id ). Is that the way I should set up the foreign keys? Is the foreign key from C->A necessary? Or do I even need foreign keys at all given that all those columns are part of the primary keys? Thanks.

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• How do I use Eval() to reference values in a SortedDictionary in an asp Repeater?

  - by MatthewMartin

  I thought I was clever to switch from the memory intensive DataView to SortedDictionary as a memory efficient sortable data structure. Now I have no idea how get the key and value out of the datasource in the <%# or Eval() expressions. SortedDictionary<int, string> data = RetrieveNames(); rCurrentTeam.DataSource = data; rCurrentTeam.DataBind(); <asp:Repeater ID="rNames" runat="server"> <ItemTemplate> <asp:Label ID="lblName" runat="server" Text='<%# Eval("what?") %>' /> </ItemTemplate> </asp:Repeater> Any suggestions?

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• How to open a large text file in C#

  - by desmati

  I have a text file that contains about 100000 articles. The structure of file is: BEGIN OF FILE .Document ID 42944-YEAR:5 .Date 03\08\11 .Cat political Article Content 1 .Document ID 42945-YEAR:5 .Date 03\08\11 .Cat political Article Content 2 END OF FILE I want to open this file in c# for processing it line by line. I tried this code: String[] FileLines = File.ReadAllText(TB_SourceFile.Text).Split(Environment.NewLine.ToCharArray()); But it says: Exception of type 'System.OutOfMemoryException' was thrown. The question is How can I open this file and read it line by line. File Size: 564 MB (591,886,626 bytes) File Encoding: UTF-8 File contains Unicode characters.

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• Generic WithEvents

  - by serhio

  Error: 'WithEvents' variables can only be typed as classes, interfaces or type parameters with class constraints Background: Public Class Tadpole(Of T As IVisibleChanged, P As IVisibleChanged) Private WithEvents _Tad As T ' ERROR ' Private WithEvents _Pole As P ' ERROR ' Public Property Tad() As T ... Public Property Pole() As P ... End Class ''' IVisibleChanged ''' Public Interface IVisibleChanged Property Visible() As Boolean Event VisibleChanged As EventHandler End Interface Workaround: a. Use AddHandler to handle events defined in a structure. EDIT b. use Private WithEvents _Tad AsIVisibleChanged (M.A. Hanin) c. ?

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• Parent Child Relationships with Fluent NHibernate?

  - by ElHaix

  I would like to create a cascading tree/list of N number of children for a given parent, where a child can also become a parent. Given the following data structure: CountryType=1; ColorType=3; StateType=5 6,7,8 = {Can, US, Mex} 10, 11, 12 = {Red, White, Blue} 20,21,22= {California, Florida, Alberta} TreeID ListTypeID ParentTreeID ListItemID 1 1 Null 6 (Canada is a Country) 2 1 Null 7 (US is a Country) 3 1 Null 8 (Mexico is a Country) 4 3 3 10 (Mexico has Red) 5 3 3 11 (Mexico has White) 6 5 1 22 (Alberta is in Canada) 7 5 7 20 (California is in US) 8 5 7 21 (Florida is in US) 9 3 6 10 (Alberta is Red) 10 3 6 12 (Alberta is Blue) 11 3 2 10 (US is Red) 12 3 2 11 (Us is Blue) How would this be represented in Fluent NHibernate classes? Some direction would be appreciated. Thanks.

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• Umbraco -- controlling access to media by membership

  - by Ryan

  I need to set up access to media files with the following structure: A media folder is designated as belonging to a specific member group. Then, a sub-folder below that needs to be available to a subset of members from the parent's member group. Any thoughts on how this can best be accomplished? I'll render the actual file download links with a user control, but how should I set up this access control on the back end? I need a member-group picker and a multiple member picker. Do these exist anywhere?

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• XML, XPATH adding values

  - by user575373

  hello, i have XML files which contain records with the following structure: <payment contractType="1"> <income type="0"> <gr code="1" amount="1506.00"/> <gr code="4" amount="35.00"/> <gr code="10" amount="288.14"/> <de code="3011300" amount="138.72"/> <de code="3081100" amount="48.81"/> <de code="3082400" amount="109.84"/> </income> <netAmount1 value="765.00"/> <netAmount2 value="765.00"/> </payment> each file has many records of type payment and i want the final xml to contain one payment record by adding all the amount values for every differrent code value I think XPath can be used for this, but I never used it before , could someone show me some Java (or else) code for this?

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• .NET Reflector and getters/setters issue

  - by Humberto

  I'm using an up-to-date .NET Reflector to disassemble an internal legacy app whose source code is almost impossible to recover. I need to find the cause of a nasty bug, and then possibly patch it. Reflector did a good job as usual in the re-creation of the project's structure, but soon I discovered that every property call was left "expanded" to its get_() and set_() method signatures, rendering the source code impossible to compile. A quick Visual Studio "Search/Replace" with regex solved these cases, but it's awkward. Is there a way to make Reflector behave correctly?

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• Loading all files in a directory in a Java applet

  - by WarrenB

  How would one go about programatically loading all the resource files in a given directory in a JAR file for an applet? The resources will probably change several times over the lifetime of the program so I don't want to hardcode names in. Normally I would just traverse the directory structure using File.list(), but I get permission issues when trying to do that within an applet. I also looked at using an enumeration with something line ClassLoader.getResources() but it only finds files of the same name within the JAR file. Essentially what I want to do is (something like) this: ClassLoader imagesURL = this.getClass().getClassLoader(); MediaTracker tracker = new MediaTracker(this); Enumeration<URL> images = imagesURL.getResources("resources/images/image*.gif"); while (images.hasMoreElements()){ tracker.add(getImage(images.nextElement(), i); i++; } I know I'm probably missing some obvious function, but I've spent hours searching through tutorials and documentation for a simple way to do this within an unsigned applet.

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• SQL indexing on varchar

  - by alex

  I have a table whose columns are varchar(50) and a float - I need to (very quickly) look get the float associated with a given string. Even with indexing, this is rather slow. I know, however, that each string is associated with an integer, which I know at the time of lookup, so that each string maps to a unique integer, but each integer does not map to a unique string. One might think of it as a tree structure. Is there anything to be gained by adding this integer to the table, indexing on it, and using a query like SELECT floatval FROM mytable WHERE phrase=givenstring AND assoc=givenint? This is Postgres, and if you couldn't tell, I have very little experience with databases.

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