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  • A B+tree simple implementation in C

    - by initpy
    Hi guys, I'm working on a fun project where I need a simple key/value store that uses B+Trees. I studied them some years ago, and to be honest, I don't want to reinvent the wheel, so I'm looking for a simple implementation in C of b+tree that I can just include in my project. I know of sqlite's, dbm's and tokyocabinet's ones but they're a little too "complicated" for my needs. Is there any (even pedagogical) work on this you can refer me to? Do you have some code to share? Thanks a lot!

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  • How to implement arrays in an interpreter?

    - by Ray
    I have managed to write several interpreters including Tokenizing Parsing, including more complicated expressions such as ((x+y)*z)/2 Building bytecode from syntax trees Actual bytecode execution What I didn't manage: Implementation of dictionaries/lists/arrays. I always got stuck with getting multiple values into one variable. My value structure (used for all values passed around, including variables) looks like this, for example: class Value { public: ValueType type; int integerValue; string stringValue; } Works fine with integers and strings, but how could I implement arrays? (From now on with array I mean arrays in my experimental language, not in C++) How can I fit the array concept into the Value class above? Is it possible? How should I make arrays able to be passed around just as you could pass around integers and strings in my language, using the class above? Accessing array elements or memory allocation wouldn't be the problem, I just don't know how to store them.

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  • A datastructure for Robotic Sort

    - by amit.codename13
    I am trying to solve this problem : https://www.spoj.pl/problems/CERC07S/ I have identified that i need a datastructure in which reversing operations have lesser time complexity. I tried to create one using a doubly linked list, in which (i thought) reversing can be done in O(1) by just changing a value associated with the starting and ending node which indicates the direction of traversing the list. I tried to implement it but got stuck. Maybe the approach is wrong! Are trees applicable here? If yes, how? Any ideas or links are appreciated? Thanks in advance.

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  • How do I learn Flash Game Development?

    - by grokker
    I'm currently a PHP programmer and one of my childhood dreams is to create a game. The problem is I don't know Flash. I'm not great at drawing stuff or even artistic. I could program a little with JavaScript and I could consider myself intermediate with JQuery. Question How do I get started with Flash Game development? What books do I read first? The type of game is a side scroller about an Indiana Jones type of character and the setting is on the jungle with trees and snakes and a lot of animals.

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  • Add rules (filters) to ftp programs to avoid uploading certain files/folders

    - by guisasso
    i use Filezilla as my ftp client, but this question goes to any other client that could be useful. Can i (in any client) add rules (filters) to an ftp program to avoid upload of certain files or folders? For example: Expression web creates those annoying _vti_cnf folders, or, certain folders in which i have the original version of a picture without a watermark that i don't want to upload. Example, i have a folder A, that has sub folders "original" and "current", i would like to add a filter, so every time i select A to be uploaded, "original" wouldn't go, but "current would".

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  • Learning Blend with .toolbox (Silverlight TV #29)

    In this episode, Arturo Toledo demonstrates all of the new content he and his colleagues have created to teach you to design and develop with Expression Blend and Silverlight. He shows off some really cool samples, all of which you can download and do yourself through hands on-labs. Arturo walks through the .toolbox site and shows the numerous learning materials, videos, demos, and hands-on labs. If you have been looking for a comprehensive set of self-paced learning materials focused on designing ...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Easiest way to convert json data into objects with methods attached?

    - by John Mee
    What's the quickest and easiest way to convert my json, containing the data of the objects, into actual objects with methods attached? By way of example, I get data for a fruitbowl with an array of fruit objects which in turn contain an array of seeds thus: {"fruitbowl": [{ "name": "apple", "color": "red", "seeds": [] },{ "name": "orange", "color": "orange", "seeds": [ {"size":"small","density":"hard"}, {"size":"small","density":"soft"} ]} } That's all nice and good but down on the client we do stuff with this fruit, like eat it and plant trees... var fruitbowl = [] function Fruit(name, color, seeds){ this.name = name this.color = color this.seeds = seeds this.eat = function(){ // munch munch } } function Seed(size, density){ this.size = size this.density = density this.plant = function(){ // grow grow } } My ajax's success routine currently is currently looping over the thing and constructing each object in turn and it doesn't handle the seeds yet, because before I go looping over seed constructors I'm thinking Is there not a better way? success: function(data){ fruitbowl.length = 0 $.each(data.fruitbowl, function(i, f){ fruitbowl.push(new Fruit(f.name, f.color, f.seeds)) }) I haven't explored looping over the objects as they are and attaching all the methods. Would that work?

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  • What data is actually stored in a B-tree database in CouchDB?

    - by Andrey Vlasovskikh
    I'm wondering what is actually stored in a CouchDB database B-tree? The CouchDB: The Definitive Guide tells that a database B-tree is used for append-only operations and that a database is stored in a single B-tree (besides per-view B-trees). So I guess the data items that are appended to the database file are revisions of documents, not the whole documents: +---------|### ... | | +------|###|------+ ... ---+ | | | | +------+ +------+ +------+ +------+ | doc1 | | doc2 | | doc1 | ... | doc1 | | rev1 | | rev1 | | rev2 | | rev7 | +------+ +------+ +------+ +------+ Is it true? If it is true, then how the current revision of a document is determined based on such a B-tree? Doesn't it mean, that CouchDB needs a separate "view" database for indexing current revisions of documents to preserve O(log n) access? Wouldn't it lead to race conditions while building such an index? (as far as I know, CouchDB uses no write locks).

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  • Mousin' down the PathListBox

    - by T
    While modifying the standard media player with a new look and feel for Ineta Live I saw a unique opportunity to use their logo with a dotted I with and attached arc as the scrub control. So I created a PathListBox that I wanted an object to follow when a user did a click and drag action.  Below is how I solved the problem.  Please let me know if you have improvements or know of a completely different way.  I am always eager to learn. First, I created a path using the pen tool in Expression Blend (see the yellow line in image below).  Then I right clicked that path and chose [Path] --> [Make Layout Path].   That created a new PathListBox.  Then I chose the object I want to move down the new PathListBox and Placed it as a child in the Objects and Timeline window (see image below).  If the child object (the thing the user will click and drag) is XAML, it will move much smoother than images. Just as another side note, I wanted there to be no highlight when the user selects the “ball” to drag and drop.  This is done by editing the ItemContainerStyle under Additional Templates on the PathListBox.  Post a question if you need help on this and I will expand my explanation. Here is a pic of the object and the path I wanted it to follow.  I gave the path a yellow solid brush here so you could see it but when I lay this over another object, I will make the path transparent.   To animate this object down the path, the trick is to animate the Start number for the LayoutPath.  Not the StartItemIndex, the Start above Span. In order to enable animation when a user clicks and drags, I put in the following code snippets in the code behind. the DependencyProperties are not necessary for the Drag control.   namespace InetaPlayer { public partial class PositionControl : UserControl { private bool _mouseDown; private double _maxPlayTime; public PositionControl() { // Required to initialize variables InitializeComponent(); //mouse events for scrub control positionThumb.MouseLeftButtonDown += new MouseButtonEventHandler(ValueThumb_MouseLeftButtonDown); positionThumb.MouseLeftButtonUp += new MouseButtonEventHandler(ValueThumb_MouseLeftButtonUp); positionThumb.MouseMove += new MouseEventHandler(ValueThumb_MouseMove); positionThumb.LostMouseCapture += new MouseEventHandler(ValueThumb_LostMouseCapture); } // exposed for binding to real slider using a DependencyProperty enables animation, styling, binding, etc.... public double MaxPlayTime { get { return (double)GetValue(MaxPlayTimeProperty); } set { SetValue(MaxPlayTimeProperty, value); } } public static readonly DependencyProperty MaxPlayTimeProperty = DependencyProperty.Register("MaxPlayTime", typeof(double), typeof(PositionControl), null);   // exposed for binding to real slider using a DependencyProperty enables animation, styling, binding, etc....   public double CurrSliderValue { get { return (double)GetValue(CurrSliderValueProperty); } set { SetValue(CurrSliderValueProperty, value); } }   public static readonly DependencyProperty CurrSliderValueProperty = DependencyProperty.Register("CurrSliderValue", typeof(double), typeof(PositionControl), new PropertyMetadata(0.0, OnCurrSliderValuePropertyChanged));   private static void OnCurrSliderValuePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { PositionControl control = d as PositionControl; control.OnCurrSliderValueChanged((double)e.OldValue, (double)e.NewValue); }   private void OnCurrSliderValueChanged(double oldValue, double newValue) { _maxPlayTime = (double) GetValue(MaxPlayTimeProperty); if (!_mouseDown) if (_maxPlayTime!=0) sliderPathListBox.LayoutPaths[0].Start = newValue / _maxPlayTime; else sliderPathListBox.LayoutPaths[0].Start = 0; }   //mouse control   void ValueThumb_MouseMove(object sender, MouseEventArgs e) { if (!_mouseDown) return; //get the offset of how far the drag has been //direction is handled automatically (offset will be negative for left move and positive for right move) Point mouseOff = e.GetPosition(positionThumb); //Divide the offset by 1000 for a smooth transition sliderPathListBox.LayoutPaths[0].Start +=mouseOff.X/1000; _maxPlayTime = (double)GetValue(MaxPlayTimeProperty); SetValue(CurrSliderValueProperty ,sliderPathListBox.LayoutPaths[0].Start*_maxPlayTime); }   void ValueThumb_MouseLeftButtonUp(object sender, MouseButtonEventArgs e) { _mouseDown = false; } void ValueThumb_LostMouseCapture(object sender, MouseEventArgs e) { _mouseDown = false; } void ValueThumb_MouseLeftButtonDown(object sender, MouseButtonEventArgs e) { _mouseDown = true; ((UIElement)positionThumb).CaptureMouse(); }   } }   I made this into a user control and exposed a couple of DependencyProperties in order to bind it to a standard Slider in the overall project.  This control is embedded into the standard Expression media player template and is used to replace the standard scrub bar.  When the player goes live, I will put a link here.

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  • Select in a many-to-many relationship in MySQL

    - by Joff Williams
    I have two tables in a MySQL database, Locations and Tags, and a third table LocationsTagsAssoc which associates the two tables and treats them as a many-to-many relationship. Table structure is as follows: Locations --------- ID int (Primary Key) Name varchar(128) LocationsTagsAssoc ------------------ ID int (Primary Key) LocationID int (Foreign Key) TagID int (Foreign Key) Tags ---- ID int (Primary Key) Name varchar(128) So each location can be tagged with multiple tagwords, and each tagword can be tagged to multiple locations. What I want to do is select only Locations which are tagged with all of the tag names supplied. For example: I want all locations which are tagged with both "trees" and "swings". Location "Park" should be selected, but location "Forest" should not. Any insight would be appreciated. Thanks!

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  • =~ (equal-sign tilde) and m" ... " in .htaccess directive

    - by Lèse majesté
    I saw this bit of code on an old forum post: SSLRequire %{HTTP_HOST} =~ m"\.secure\.powweb\.com" And I was just wondering what the =~ and m" ... " meant. I've been searching online and in the Apache documentation for any mention of the equal-sign tilde operator, but I've found no mention of it. I know that some directives can take a tilde to use a regular expression, but I've never seen the m" ... " form used before. What exactly is that m" ... " for? Where else would you see this form?

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  • Automatic language transformation in editor or IDE [on hold]

    - by Rumca
    Are there any tools that are capable of editing code but in different language? To be more concrete, I want to parse java source file in editor, compile it to my language X, edit in X and compile back to java on save. Or edit pom.xml file using non-XML syntax. Which editor or IDE would be easiest to use for implementing such prototype? Option to transform only a snippet would be ideal to limit effort on parsing. For one example, Intellij IDEA can display anonymous class so it looks like lambda expression hiding some of boilerplate.

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  • Is the phrase "never reinvent the wheel" suitable for students?

    - by Gnijuohz
    I find myself constantly running into this expression "don't reinvent the wheel" or "never reinvent the wheel" when I ask some questions on SO. They tell you to use some frameworks or existing packages. I know where this attitude is coming from since it's unwise to waste time on something others have already solved. Or it that so? As a student, I find by using some code others wrote to solve my problem I can't learn as much as I'd like to, and I gain less insight. And sometimes I think that phrase is mainly for working programmers facing deadlines and not for students like me. Is it that bad to "reinvent the wheel"? Maybe I'm thinking it wrong? Maybe there is a way I can avoid reinventing the wheel and at the same time learn a lot?

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  • "lock request time out period exceeded" Error When Trying to See DB Hierarchies

    - by Lloyd Banks
    I have a DB that I can run basic queries (albeit much slower than normal) off of. When I try to see the hierarchy trees for tables, views, or procedures in SSMS Object Explorer, I get the "lock request time out period exceeded". My Report Server reports that run off of objects in this DB are no longer completing. Jobs associated with procedures stored on this DB also do not run. I tried using sp_who2 to find and kill all connections on the DB. This has not solved the problem. What is going on here? How can I resolve this?

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  • Quel est le bug le plus récalcitrant que vous ayez rencontré ? Improbable ou impossible à reproduire, racontez-nous tout

    Quel est le bug le plus récalcitrant que vous ayez rencontré ? Improbable ou impossible à reproduire, racontez-nous votre meilleure histoire de débogage Si le débogage est l'art d'enlever les bogues, la programmation doit être l'art de les créer. Une expression chère à beaucoup de développeurs qui souligne à quel point le débogage d'une application peut être important et... problématique. C'est ce que relate Patrick Thomson, un développeur blogueur qui raconte ce qu'il qualifie de "meilleure histoire de débogage qu'il ait jamais entendue". Il s'agit d'une mésaventure vécue dans les année 80 par le père de l'auteur, avec un ordinateur ancestrale ut...

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  • LINQ/LAMBDA filter query by date [on hold]

    - by inquisitive_one
    I'm trying to use LINQ to SQL to retrieve earnings data for a particular date range. Currently the table is set up as follows: Comp Eps Year Quarter IBM .5 2012 2 IBM .65 2012 3 IBM .60 2012 4 IBM .5 2011 2 IBM .7 2013 1 IBM .8 2013 2 Except for Eps, all fields have a data type of string or char. Eps has a data type of double. Here's my code: var myData = myTable .Where(t => t.Comp.Equals("IBM") && Convert.Int32(string.Format("{0}{1}", t.Year, t.Quarter)) <= 20131); I get the following error when I tried that code: Method 'System.String Format(System.String, System.Object, System.Object)' has no supported translation to SQL How can I select all Eps that has a year & quarter less than "20132" using a lambda expression?

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  • Are protected constructors considered good practice?

    - by Álvaro G. Vicario
    I'm writing some little helper classes to handle trees. Basically, I have a node and a special root node that represents the tree. I want to keep it generic and simple. This is part of the code: <?php class Tree extends TreeNode{ public function addById($node_id, $parent_id, $generic_content){ if( $parent = $this->findNodeById($parent_id) ){ $parent->addChildById($node_id, $generic_content); } } } class TreeNode{ public function __construct($node_id, $parent_id, $generic_content){ // ... } protected function addChildById($node_id, $generic_content){ $this->children[] = new TreeNode($this->node_id, $node_id, $generic_content); } } $Categories = new Tree; $Categories->addById(1, NULL, $foo); $Categories->addById(2, NULL, $bar); $Categories->addById(3, 1, $gee); ?> My questions: Is it sensible to force TreeNode instances to be created through TreeNode::addById()? If it's so, would it be good practise to declare TreeNode::__construct() as private/protected?

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  • C# : Parsing information out of a path

    - by mbcrump
    If you have a path for example: \\MyServer\MyFolderA\MyFolderB\MyFile.jpg and you need to parse out the filename, directory name or the directory parent name. You should use the fileinfo class instead of a regex expression or a string split. See the example code below:   Code Snippet using System; using System.IO;   class Test {     static void Main(string[] args)     {         string file = @"\\MyServer\MyFolderA\MyFolderB\MyFile.jpg";         FileInfo fi = new FileInfo(file);         Console.WriteLine(fi.Name);                  // Prints File.jpg         Console.WriteLine(fi.Directory.Name);        // Prints FolderB         Console.WriteLine(fi.Directory.Parent.Name); // Prints FolderA     } }

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  • How to make a table view which is not the full width of the screen?

    - by mystify
    For some strange reason, UITableView resizes my cells to 320 width no matter how I set the frame for the UITableView object. Even if I go in later and resize the cell back to 250, UITableView seems to resize it again to 320 some time. Is there some property or method that must be set / called additionally to get that right? However, I can add my contents in a way that it looks like 250 width, but my whole layouting code is a big mess since I can't rely on the cell frame width which is "wrong". Also it seems like a big waste of memory since the bitmaps in the layer trees are nonsenseless 320 width instead of 250, even though the frame of the UITableView is not 320 width.

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  • Turn database result into array

    - by Industrial
    Hi everyone, I have just made the update/add/delete part for the "Closure table" way of organizing query hierarchical data that are shown on page 70 in this slideshare: http://www.slideshare.net/billkarwin/sql-antipatterns-strike-back My database looks like this: Table Categories: ID Name 1 Top value 2 Sub value1 Table CategoryTree: child parent 1 1 2 2 2 1 However, I have a bit of an issue getting the full tree back as an multidimensional array from a single query. Here's what I would like to get back: array ( 'topvalue' = array ( 'Subvalue', 'Subvalue2', 'Subvalue3' = array ('Subvalue 1', 'Subvalue 2', 'Subvalue 3' ) ); ); Update: Found this link, but I still have a hard time to convert it into an array: http://karwin.blogspot.com/2010/03/rendering-trees-with-closure-tables.html

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  • Java Error Using Loops [migrated]

    - by Shaun
    I am facing a error in Java using the method Loops. I am a basic user learning Java and I am following a book with teaches you the basics of Java. I have this problem when I use this code in my Java Program. It gives me an red line under my code. Here's my code: public class Game{ public static void main(String[] args){ for (int dex = 0; dex < 1000; dex++) { if (dex % 12 == 0) { System.out.println(“#: “ + dex); } } } } I have been following the tutorials correctly. I am a bit lost where I have gone or done wrong. I have my public static codes and such as you'd require in any Java programming. Here's are the error given): Cannot resolve method: 'Println(? , ?)' Expression expected ',' or ')' expected Unexpected Token ';' expected

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  • UUIDs in CouchDB

    - by PartlyCloudy
    I am wondering about the format UUIDs are by default represented in CouchDB. While the RFC 4122 describes UUIDs like 550e8400-e29b-11d4-a716-446655440000, CouchDB uses continuously chars like 3069197232055d39bc5bc39348a36417. I've searched some time in both their wiki and their documentation what this actually is, however without any result. Do you know whether this is either a non RFC-conform format omitting all - or is this a completely different representation of the 128 bits. The background is that I'm using Java UUIDs which are formatted as noted in the RFC. I see the advantage that the CouchDB-style is probably more handy for building internal trees, but I want to be sure to use a consistent implementation.

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  • How do I prevent a pair of XMLEvent[Reader|Writer] from splitting empty tags into start+end tags?

    - by java.is.for.desktop
    Hello, everyone! I have an understanding problem of how the following code works: XMLInputFactory xif = XMLInputFactory.newFactory(); XMLOutputFactory xof = XMLOutputFactory.newFactory(); XMLEventReader reader = xif.createXMLEventReader(/* ... */); XMLEventWriter writer = xof.createXMLEventWriter(/* ... */); writer.add(reader); The method writer.add([some reader]) reads all events from reader and writes them consequently. Sadly, following happens: The input <root><c/></root> gets transformed to <root><c><c/></root> I know, from XML point of view, these are equal trees, but not for a human ;) What can I do to get the same output? FYI: I need a XMLEvent[Reader|Writer] pair later to filter "XML events".

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  • Python: Pickling highly-recursive objects without using `setrecursionlimit`

    - by cool-RR
    I've been getting RuntimeError: maximum recursion depth exceeded when trying to pickle a highly-recursive tree object. Much like this asker here. He solved his problem by setting the recursion limit higher with sys.setrecursionlimit. But I don't want to do that: I think that's more of a workaround than a solution. Because I want to be able to pickle my trees even if they have 10,000 nodes in them. (It currently fails at around 200.) (Also, every platform's true recursion limit is different, and I would really like to avoid opening this can of worms.) Is there any way to solve this at the fundamental level? If only the pickle module would pickle using a loop instead of recursion, I wouldn't have had this problem. Maybe someone has an idea how I can cause something like this to happen, without rewriting the pickle module? Any other idea how I can solve this problem will be appreciated.

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  • Quel est le bogue le plus récalcitrant que vous ayez rencontré ? Improbable ou impossible à reproduire, racontez-nous tout

    Quel est le bug le plus récalcitrant que vous ayez rencontré ? Improbable ou impossible à reproduire, racontez-nous votre meilleure histoire de débogage Si le débogage est l'art d'enlever les bogues, la programmation doit être l'art de les créer. Une expression chère à beaucoup de développeurs qui souligne à quel point le débogage d'une application peut être important et... problématique. C'est ce que relate Patrick Thomson, un développeur blogueur qui raconte ce qu'il qualifie de "meilleure histoire de débogage qu'il ait jamais entendue". Il s'agit d'une mésaventure vécue dans les année 80 par le père de l'auteur, avec un ordinateur ancestrale ut...

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