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• Kids and programming: ScratchKara

  - by Mike Pagel

  Ever now and then I kept wondering how to share with my kids the excitement of creating something with your computer. Of course, today this is a bit more difficult, as they have seen 3D animation games and well-edited websites. I guess that's why they weren't all that hyped when I found my first computer model at our local recycling facilities (an 8-bit Laser VZ-200 with rubber keys). When I finally got it up and running with an old analog TV set they finally asked whether we could play soccer on it. Needless to say that my showing them how it remembers some BASIC commands and lists and executes them did not make any impression. So the question is for real: How do you get today's kids excited about programming? And just recently I looked again for environments that allow even young kids (mine are 7 and 9 years old now) to do something and have fun. Obviously any real, text-oriented programming language wouldn't work well. To cut it short: Something really nice was built by University of Oldenburg: ScratchKara. It is the perfect mixture of Kara, a simulation of a little ladybug and Scratch, an authoring environment from MIT. ScratchKara allows kids to initially simply explore how the bug moves and turns by pressing the action buttons, then move towards sequencing commands through drag & drop, and eventually end up building algorithms with procedures and functions. Even through it is built for kids and beginners, the environment comes with debugging and refactoring, which I found more than amazing. My kids love it and I have to admit I keep thinking about how to solve a bit more advanced problems with this language, which does not allow you to store any state information (other than your call stack). Yes, I am hooked, too... Once the language is understood you can then move to one of the original Kara versions, where you can define the bug's behavior through finite statemachines, Turing tables, Java and other textual languages. And from there, anything is possible.

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• CodePlex Daily Summary for Saturday, September 15, 2012

  CodePlex Daily Summary for Saturday, September 15, 2012Popular ReleasesMCEBuddy 2.x: MCEBuddy 2.2.15: Changelog for 2.2.15 (32bit and 64bit) 1. Added support for %originalfilepath% to get the source file full path. Used for custom commands only. 2. Added support for better parsing of Media Portal XML files to extract ShowName and Episode Name and download additional details from TVDB (like Season No, Episode No etc). 3. Added support for TVDB seriesID in metadata 4. Added support for eMail non blocking UI testCrashReporter.NET : Exception reporting library for C# and VB.NET: CrashReporter.NET 1.2: *Added html mail format which shows hierarchical exception report for better understanding.VCC: Latest build, v2.3.00914.0: Automatic drop of latest buildScarlet Road: Scarlet Road Test Build 007: Playable game. Includes source.DotNetNuke Search Engine Sitemaps Provider: Version 02.00.00: New release of the Search Engine Sitemap Providers New version - not backwards compatible with 1.x versions New sandboxing to prevent exceptions in module providers interfering with main provider Now installable using the Host->Extensions page New sitemaps available for Active Forums and Ventrian Property Agent Now derived from DotNetNuke Provider base for better framework integration DotNetNuke minimum compatibility raised to DNN 5.2, .NET to 3.5PDF Viewer Web part: PDF Viewer Web Part: PDF Viewer Web PartChris on SharePoint Solutions: View Grid Banding - v1.0: Initial release of the View Creation and Management Page Column Selector Banding solution.$linq - A Javascript LINQ library: Version 1.0: Version 1.0 Initial releasePowerConverter: PowerConverter Beta: This is the first release of PowerConverter. Allows for converting PE code to Power code.NetView Control for Microsoft Access: DevVersion 19852 - More Databinding and Resizing: NetView Renamed event GotFocus to Clicked Added events Clicked/DoubleClicked Added event BackgroundDoubleClicked Changed nomenclature for world coordinates to (Position1, Position2)|Extent1xExtent2 Renamed Locked -> Readonly Added properties Minimum1/Maximum1 and Minimum2/Maximum2 Removed NetView.DeviceDefinitionArea, obsolete properties Support for resizing Added properties BackColor and BorderColor NetView Properties form added binding field for BusinessId propagate erro...Runtime Dynamic Data Model Builder: Main Library Version 1.0.0.0: Main Library Version 1.0.0.0Microsoft Ajax Minifier: Microsoft Ajax Minifier 4.67: Fix issue #18629 - incorrectly handling null characters in string literals and not throwing an error when outside string literals. update for Issue #18600 - forgot to make the ///#DEBUG= directive also set a known-global for the given debug namespace. removed the kill-switch for disregarding preprocessor define-comments (///#IF and the like) and created a separate CodeSettings.IgnorePreprocessorDefines property for those who really need to turn that off. Some people had been setting -kil...Lakana - WPF Framework: Lakana V2: Lakana V2 contains : - Lakana WPF Forms (with sample project) - Lakana WPF Navigation (with sample project)Microsoft SQL Server Product Samples: Database: OData QueryFeed workflow activity: The OData QueryFeed sample activity shows how to create a workflow activity that consumes an OData resource, and renders entity properties in a Microsoft Excel 2010 worksheet or Microsoft Word 2010 document. Using the sample QueryFeed activity, you can consume any OData resource. The sample activity uses LINQ to project OData metadata into activity designer expression items. By setting activity expressions, a fully qualified OData query string is constructed consisting of Resource, Filter, Or...Arduino for Visual Studio: Arduino 1.x for Visual Studio 2012, 2010 and 2008: Register for the visualmicro.com forum for more news and updates Version 1209.10 includes support for VS2012 and minor fixes for the Arduino debugger beta test team. Version 1208.19 is considered stable for visual studio 2010 and 2008. If you are upgrading from an older release of Visual Micro and encounter a problem then uninstall "Visual Micro for Arduino" using "Control Panel>Add and Remove Programs" and then run the install again. Key Features of 1209.10 Support for Visual Studio 2...Social Network Importer for NodeXL: SocialNetImporter(v.1.5): This new version includes: - Fixed the "resource limit" bug caused by Facebook - Bug fixes To use the new graph data provider, do the following: Unzip the Zip file into the "PlugIns" folder that can be found in the NodeXL installation folder (i.e "C:\Program Files\Social Media Research Foundation\NodeXL Excel Template\PlugIns") Open NodeXL template and you can access the new importer from the "Import" menuAcDown????? - AcDown Downloader Framework: AcDown????? v4.1: ??●AcDown??????????、??、??、???????。????，????，?????????????????????????。???????????Acfun、????(Bilibili)、??、??、YouTube、??、???、??????、SF????、????????????。 ●??????AcPlay?????，??????、????????????????。 ● AcDown??????????????????，????????????????????????????。 ● AcDown???????C#??，????.NET Framework 2.0??。?????"Acfun?????"。 ????32??64? Windows XP/Vista/7/8 ???? 32??64? ???Linux ????(1)????????Windows XP???,?????????.NET Framework 2.0???(x86)，?????"?????????"??? (2)???????????Linux???，????????Mono?? ??...Move Mouse: Move Mouse 2.5.2: FIXED - Minor fixes and improvements.MVC Controls Toolkit: Mvc Controls Toolkit 2.3: Added The new release is compatible with Mvc4 RTM. Support for handling Time Zones in dates. Specifically added helper methods to convert to UTC or local time all DateTimes contained in a model received by a controller, and helper methods to handle date only fileds. This together with a detailed documentation on how TimeZones are handled in all situations by the Asp.net Mvc framework, will contribute to mitigate the nightmare of dates and timezones. Multiple Templates, and more options to...DNN Metro7 style Skin package: Metro7 style Skin for DotNetNuke 06.02.00: Maintenance Release Changes on Metro7 06.02.00 Fixed width and height on the jQuery popup for the Editor. Navigation Provider changed to DDR menu Added menu files and scripts Changed skins to Doctype HTML Changed manifest to dnn6 manifest file Changed License to HTML view Fixed issue on Metro7/PinkTitle.ascx with double registering of the Actions Changed source folder structure and start folder, so the project works with the default DNN structure on developing Added VS 20...New ProjectsBizTalk Zombie Management: A powerful tool to handle zombie. As a service you can monitor all zombie instance and process them. For the moment only file is supporting.bxkw8: oooooooooooh long johnsonCellularSolver: The main idea of a this project - create cellular automation (CA) simulation system. We try to reduce ODE/PDE/Integral Equations models to CA-modelEAWebService: EAWebService is web service that executes parallel evolutionary algorithm. Finite Element Method Samples with C#: Finite Element Method Samples with C# Game Jolt C# Trophy API: The Game Jolt Trophy API provides dotNET developers with access to the Game Jolt services including Trophies, High Scores, Data Storage and many more.GNSystem: GNSystem is a simple (yet, no so elegant) Web-Application which contains a Forum system and a CMS\Blog system. GNSystem is written in ASP.Net MVC 4 using C#Hospital Management System (HMS): HMS is a software basically working to make the hospital management much easier and fasterInfinity - WPF.MVC: Framework for WPF/SL/WinFormsKindle: Kindle PublisherMetroCash: A personal finance management programmetroCIS: metroCIS - Eine open-source Anwendung für Windows8 Verwalte dein Studium an der FH Technikum Wien mit dieser App und erleichter dir damit dein Studentenleben.MTAC: MTAC, for My Tfs Administration Center, is a centralized administration tool for TFSMyStart: Create an Open Source implementation of the Windows Start Menu (based initially on Windows 7), to be used on Windows 8.NLite Data Framework: NLite Linq ORM frameworkPDF Viewer Web part: Here now presenting PDF Viewer web part solution with code. Project91405: dfgfdgfdrProject91407: awqwqProject91407M: 111Purchasesales(??????): a simple Sales Manage Project.QueryOver Specification: A simple implementation of the Specification Pattern using NHibernate QueryOver.Shopping Analytics: Esta aplicacion muestra como aprovechar diversas caracteristicas de la plataforma Windows Phone.simbo: Simbo is a simple, fun app for sharing small notes with friends where many of the concepts in your note can be represented by a symbols.SISLOG: El sistema de logística SISLOG es un software que cual será capaz de automatizar y optimizar los procesos que se llevan a cabo en el área de logística.SQL Server Scripts - A RSSUG CodePlex Project: The SQL Server Scripts project is dedicated to supplying high quality scripts to help with the maintenance and development of SQL Server in every environment.Talqum.League: Talqum.League is a League organisator and statistics app.The Pratoriate Foundation: used for all software dev projects for the non profit Pratoriate Foundation.

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• Per-vertex animation with VBOs: Stream each frame or use index offset per frame?

  - by charstar

  Scenario Meshes are animated using either skeletons (skinned animation) or some form of morph targets (i.e. per-vertex key frames). However, in either case, the animations are known in full at load-time, that is, there is no physics, IK solving, or any other form of in-game pose solving. The number of character actions (animations) will be limited but rich (hand-animated). There may be multiple characters using a each mesh and its animations simultaneously in-game (they will be at different poses/keyframes at the same time). Assume color and texture coordinate buffers are static. Goal To leverage the richness of well vetted animation tools such as Blender to do the heavy lifting for a small but rich set of animations. I am aware of additive pose blending like that from Naughty Dog and similar techniques but I would prefer to expend a little RAM/VRAM to avoid implementing a thesis-ready pose solver. I would also like to avoid implementing a key-frame + interpolation curve solver (reinventing Blender vertex groups and IPOs). Current Considerations Much like a non-shader-powered pose solver, create a VBO for each character and copy vertex and normal data to each VBO on each frame (VBO in STREAMING). Create one VBO for each animation where each frame (interleaved vertex and normal data) is concatenated onto the VBO. Then each character simply has a buffer pointer offset based on its current animation frame (e.g. pointer offset = (numVertices+numNormals)*frameNumber). (VBO in STATIC) Known Trade-Offs In 1 above: Each VBO would be small but there would be many VBOs and therefore lots of buffer binding and vertex copying each frame. Both client and pipeline intensive. In 2 above: There would be few VBOs therefore insignificant buffer binding and no vertex data getting jammed down the pipe each frame, but each VBO would be quite large. Are there any pitfalls to number 2 (aside from finite memory)? Are there other methods that I am missing?

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• Interpolation between two 3D points?

  - by meds

  I'm working with some splines which define a path a character follows (you can see a gameplay video here to get a better understanding of what's going on: http://www.youtube.com/watch?v=BndobjOiZ6g). Basically the characters 'forward' look direction is set to the 'forward' direction of the spline and when players tilt their phone left and right the character is strafed along its 'right' coordinate. The issue with this is (rather obviously) in performance, interpolating over a spline to find the nearest position and tangent relative to the player is an incredibly costly operation. To get by this I cache a finite number of positions in what I call 'SplineDetails', the class is as follows: public class SplineDetails { public SplineDetails() { Forward = Vector3.forward; Position = Vector3.one * float.MaxValue; Alpha = -1; } public float Alpha; // [0,1] measured along length of spline where 0 is the initial point and 1 is the end point of the spline public Vector3 Position; // the point of the spline at this alpha public Vector3 Forward; // the forward tangent of the spline at this alpha } I populate this with say 30 coordinates and I can give a rough estimate of a coordinate and 'forward' based on a position past in. It's not as accurate but it's much faster. But now I'd like to make the system work better by estimating positions and 'forward' directions by interpolating between two of the cached points though I'm stuck trying to figure out some logic. My first problem is, how can I determine between which two points the object is? Given each point can be placed at different intervals along the spline it could mean that two points in front or behind the object can be closer to the object. The other problem is to figure out the proportion between the two paths it's between, i.e. if there is a point a at coordinate (0,0,0) and point b at coordinate (1,0,0) if the object is at position (0.5,0,0) then the result it should give is '0.5' (as it is equal distance away from point a and point b). That's a simple example, but what if the object is at coordinate (0.5,3,0) for example?

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• I have discovered a fundamental truth about TV shows and plots

  - by Steve Loethen

  For years, we have all known (okay, maybe I give people too much credit) that there is a very small finite number of plots.  I propose a project.  Let’s use the blogosphere to catalog those plotlines, and then find and document the episodes of shows that use them, including the show title. As evidence, how many shows have used the following plot line:? The standard “evil twin” plotline?  Once relegated to soaps, it has show up in crime shows, with the twist of DNA.  Step one, concentrate one this one.  Tell me about every show you recall that has used this plot.  I will collect and document the shows on my website (www.loethen.net) and we can build a database of the plots. Step two, what other common themes should I offer up?  How about the bigamist plot line?  The “bad guy was dead” plot line (revenge from the dead"?  The “vast government conspiracy” plotline? Let the games begin….

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• Who can change the View in MVC?

  - by Luke

  I'm working on a thick client graph displaying and manipulation application. I'm trying to apply the MVC pattern to our 3D visualization component. Here is what I have for the Model, View, and Controller: Model - The graph and it's metadata. This includes vertices, edges, and the attributes of each. It does not contain position information, icons, colors, or anything display related. View - This would commonly be called a scene graph. It includes the 3D display information, texture information, color information, and anything else that is related specifically to the visualization of the model. Controller - The controller takes the view and displays it in a Window using OpenGL (but it could potentially be any 3D graphics package). The application has various "layouts" that change the position of the vertices in the display. For instance, one layout may arrange the vertices in a circle. Is it common for these layouts to access and change the view directly? Should they go through the Controller to access the View? If they go through the Controller, should they just ask for direct access to the View or should each change go through the controller? I realize this is a bit different from the standard MVC example where there a finite number of Views. In this case, the View can change in an infinite number of ways. Perhaps I'm shattering some basic principle of MVC here. Thanks in advance!

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• Entry level engineer question regarding memory mangement

  - by Ealianis

  It has been a few months since I started my position as an entry level software developer. Now that I am past some learning curves (e.g. the language, jargon, syntax of VB and C#) I'm starting to focus on more esoteric topics, as to write better software. A simple question I presented to a fellow coworker was responded with "I'm focusing on the wrong things." While I respect this coworker I do disagree that this is a "wrong thing" to focus upon. Here was the code (in VB) and followed by the question. Note: The Function GenerateAlert() returns an integer. Dim alertID as Integer = GenerateAlert() _errorDictionary.Add(argErrorID, NewErrorInfo(Now(), alertID)) vs... _errorDictionary.Add(argErrorID, New ErrorInfo(Now(), GenerateAlert())) I originally wrote the ladder and rewrote it with the "Dim alertID" so that someone else might find it easier to read. But here was my concern and question. "Should one write this with the Dim AlertID, it would in fact take up more memory; finite but more, and should this method be called many times could it lead to an issue? How will .NET handle this object AlertID. Outside of .NET should one manually dispose of the object after use (near the end of the sub)." I want to ensure I become a knowledgeable programmer that does not just rely upon garbage collection. Am I over thinking this? Am I focusing on the wrong things?

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• How do I simplify a 2D game grid for level management while keeping its by-pixel features?

  - by Eric Thoma

  (I cross-posted this from StackOverflow as this seems to be a more appropriate forum. I've looked around a little here and I did not find an answer, so I hope this is not a recurring question.) This is a question dealing with 2D world design. I am playing around by creating a 2D bird's eye view shooter game, and I am looking to make the game sleek and advanced. I hope to be able to write physics so projectiles have momentum and knock-down properties. I am immediately running into the problem of world design. I need a way to have level files that store everything there is about a game. This is easiest by just having a grid of objects. But there are thin-walls and other objects that don't seem to fit into a traditional cell of a grid. I want to be able to fit all these together so I can streamline level design; so I don't have to put in the exact pixel-specific start and end of a wall. There doesn't seem to be an obvious translation from level file to game without forcing myself into a pacman-life scenario, meaning a scenario where the game feels boxy and discrete. There is a contrast between the smoothly (relatively) moving characters and finite jumps in a grid. I would appreciate an answer that would describe implementation options or point me to resources that do. I would also appreciate references to sites that teach game design. The language I am using is Java (although I would love to use C or C++, but I can never find convenient resources in those languages). Thank you for any answers. Please leave any questions in the space below; I will be able to answer them later tonight (28th Nov).

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• AI agents with FSM: a question regarding this

  - by Prog

  Finite State Machines implemented with the State design pattern are a common way to design AI agents. I am familiar with the State design pattern and know how to implement it. However I have a question regarding how this is used in games to design AI agents. Please consider a class Monster that represents an AI agent. Simplified it looks like this: class Monster{ State state; // other fields omitted public void update(){ // called every game-loop cycle state.execute(this); } public void setState(State state){ this.state = state; } // irrelevant stuff omitted } There are several State subclasses that implement execute() differently. So far classic State pattern. Here's my question: AI agents are subject to environmental effects and other objects communicating with them. For example an AI agent might tell another AI agent to attack (i.e. agent.attack()). Or a fireball might tell an AI agent to fall down. This means that the agent must have methods such as attack() and fallDown(), or commonly some message receiving mechanism to understand such messages. My question is divided to two parts: 1- Please say if this is correct: With an FSM, the current State of the agent should be the one taking care of such method calls - i.e. the agent delegates to the current state upon every event. Correct? Or wrong? 2- If correct, than how is this done? Are all states obligated by their superclass) to implement methods such as attack(), fallDown() etc., so the agent can always delegate to them on almost every event? Or is it done in some other way?

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• Entry level engineer question regarding memory management

  - by Ealianis

  It has been a few months since I started my position as an entry level software developer. Now that I am past some learning curves (e.g. the language, jargon, syntax of VB and C#) I'm starting to focus on more esoteric topics, as to write better software. A simple question I presented to a fellow coworker was responded with "I'm focusing on the wrong things." While I respect this coworker I do disagree that this is a "wrong thing" to focus upon. Here was the code (in VB) and followed by the question. Note: The Function GenerateAlert() returns an integer. Dim alertID as Integer = GenerateAlert() _errorDictionary.Add(argErrorID, NewErrorInfo(Now(), alertID)) vs... _errorDictionary.Add(argErrorID, New ErrorInfo(Now(), GenerateAlert())) I originally wrote the latter and rewrote it with the "Dim alertID" so that someone else might find it easier to read. But here was my concern and question: Should one write this with the Dim AlertID, it would in fact take up more memory; finite but more, and should this method be called many times could it lead to an issue? How will .NET handle this object AlertID. Outside of .NET should one manually dispose of the object after use (near the end of the sub). I want to ensure I become a knowledgeable programmer that does not just rely upon garbage collection. Am I over thinking this? Am I focusing on the wrong things?

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• Database - Designing an "Events" Table

  - by Alix Axel

  After reading the tips from this great Nettuts+ article I've come up with a table schema that would separate highly volatile data from other tables subjected to heavy reads and at the same time lower the number of tables needed in the whole database schema, however I'm not sure if this is a good idea since it doesn't follow the rules of normalization and I would like to hear your advice, here is the general idea: I've four types of users modeled in a Class Table Inheritance structure, in the main "user" table I store data common to all the users (id, username, password, several flags, ...) along with some TIMESTAMP fields (date_created, date_updated, date_activated, date_lastLogin, ...). To quote the tip #16 from the Nettuts+ article mentioned above: Example 2: You have a “last_login” field in your table. It updates every time a user logs in to the website. But every update on a table causes the query cache for that table to be flushed. You can put that field into another table to keep updates to your users table to a minimum. Now it gets even trickier, I need to keep track of some user statistics like how many unique times a user profile was seen how many unique times a ad from a specific type of user was clicked how many unique times a post from a specific type of user was seen and so on... In my fully normalized database this adds up to about 8 to 10 additional tables, it's not a lot but I would like to keep things simple if I could, so I've come up with the following "events" table: |------|----------------|----------------|--------------|-----------| | ID | TABLE | EVENT | DATE | IP | |------|----------------|----------------|--------------|-----------| | 1 | user | login | 201004190030 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 1 | user | login | 201004190230 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | created | 201004190031 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | activated | 201004190234 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | approved | 201004190930 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | login | 201004191200 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | created | 201004191230 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | impressed | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | blocked | 201004200319 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | deleted | 201004200320 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| Basically the ID refers to the primary key (id) field in the TABLE table, I believe the rest should be pretty straightforward. One thing that I've come to like in this design is that I can keep track of all the user logins instead of just the last one, and thus generate some interesting metrics with that data. Due to the nature of the events table I also thought of making some optimizations, such as: #9: Since there is only a finite number of tables and a finite (and predetermined) number of events, the TABLE and EVENTS columns could be setup as ENUMs instead of VARCHARs to save some space. #14: Store IPs as UNSIGNED INT with INET_ATON() instead of VARCHARs. Store DATEs as TIMESTAMPs instead of DATETIMEs. Use the ARCHIVE (or the CSV?) engine instead of InnoDB / MyISAM. Overall, each event would only consume 14 bytes which is okay for my traffic I guess. Pros: Ability to store more detailed data (such as logins). No need to design (and code for) almost a dozen additional tables (dates and statistics). Reduces a few columns per table and keeps volatile data separated. Cons: Non-relational (still not as bad as EAV): SELECT * FROM events WHERE id = 2 AND table = 'user' ORDER BY date DESC(); 6 bytes overhead per event (ID, TABLE and EVENT). I'm more inclined to go with this approach since the pros seem to far outweigh the cons, but I'm still a little bit reluctant.. Am I missing something? What are your thoughts on this? Thanks!

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• Generating strongly biased radom numbers for tests

  - by nobody

  I want to run tests with randomized inputs and need to generate 'sensible' random numbers, that is, numbers that match good enough to pass the tested function's preconditions, but hopefully wreak havoc deeper inside its code. math.random() (I'm using Lua) produces uniformly distributed random numbers. Scaling these up will give far more big numbers than small numbers, and there will be very few integers. I would like to skew the random numbers (or generate new ones using the old function as a randomness source) in a way that strongly favors 'simple' numbers, but will still cover the whole range, I.e. extending up to positive/negative infinity (or ±1e309 for double). This means: numbers up to, say, ten should be most common, integers should be more common than fractions, numbers ending in 0.5 should be the most common fractions, followed by 0.25 and 0.75; then 0.125, and so on. A different description: Fix a base probability x such that probabilities will sum to one and define the probability of a number n as xk where k is the generation in which n is constructed as a surreal number1. That assigns x to 0, x2 to -1 and +1, x3 to -2, -1/2, +1/2 and +2, and so on. This gives a nice description of something close to what I want (it skews a bit too much), but is near-unusable for computing random numbers. The resulting distribution is nowhere continuous (it's fractal!), I'm not sure how to determine the base probability x (I think for infinite precision it would be zero), and computing numbers based on this by iteration is awfully slow (spending near-infinite time to construct large numbers). Does anyone know of a simple approximation that, given a uniformly distributed randomness source, produces random numbers very roughly distributed as described above? I would like to run thousands of randomized tests, quantity/speed is more important than quality. Still, better numbers mean less inputs get rejected. Lua has a JIT, so performance can't be reasonably predicted. Jumps based on randomness will break every prediction, and many calls to math.random() will be slow, too. This means a closed formula will be better than an iterative or recursive one. 1 Wikipedia has an article on surreal numbers, with a nice picture. A surreal number is a pair of two surreal numbers, i.e. x := {n|m}, and its value is the number in the middle of the pair, i.e. (for finite numbers) {n|m} = (n+m)/2 (as rational). If one side of the pair is empty, that's interpreted as increment (or decrement, if right is empty) by one. If both sides are empty, that's zero. Initially, there are no numbers, so the only number one can build is 0 := { | }. In generation two one can build numbers {0| } =: 1 and { |0} =: -1, in three we get {1| } =: 2, {|1} =: -2, {0|1} =: 1/2 and {-1|0} =: -1/2 (plus some more complex representations of known numbers, e.g. {-1|1} ? 0). Note that e.g. 1/3 is never generated by finite numbers because it is an infinite fraction – the same goes for floats, 1/3 is never represented exactly.

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• help with number calculation algorithm [hw]

  - by sa125

  Hi - I'm working on a hw problem that asks me this: given a finite set of numbers, and a target number, find if the set can be used to calculate the target number using basic math operations (add, sub, mult, div) and using each number in the set exactly once (so I need to exhaust the set). This has to be done with recursion. So, for example, if I have the set {1, 2, 3, 4} and target 10, then I could get to it by using ((3 * 4) - 2)/1 = 10. I'm trying to phrase the algorithm in pseudo-code, but so far haven't gotten too far. I'm thinking graphs are the way to go, but would definitely appreciate help on this. thanks.

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• Ending a Rails 2 URL with an IP address causes routing error?

  - by Dave Williams

  I'm trying to construct URLs in the format http://servername/find/by/CRITERION/VALUE CRITERION is a finite set of strings, as is VALUE. Trouble is, VALUE needs to be an IP address in some situations, and it's causing me a routing error. Here's my route: map.find 'find/by/:criterion/:query', :controller => "find", :action => "by" And the error, from the Mongrel logs: Processing ApplicationController#index (for 127.0.0.1 at 2010-05-07 10:20:32) [GET] ActionController::RoutingError (No route matches "/find/by/ip/1.2.3.4" with {:method=>:get}): Rendering rescues/layout (not_found) If I visit /find/by/foo/bar or /find/by/foo/1234 I don't have problems. I suspect the problem might be Rails' inference of MIME types based on periods in the URL, but I don't really know how I can disable that. I've tried passing a :defaults = {:format = :html} to the route but that causes Mongrel to fail to start entirely. Any help appreciated!

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• Move a legend in ggplot2

  - by Dan Goldstein

  I'm trying to create a ggplot2 plot with the legend beneath the plot. The ggplot2 book says on p 112 "The position and justification of legends are controlled by the theme setting legend.position, and the value can be right, left, top, bottom, none (no legend), or a numeric position". The following code works (since "right" it is the default), and it also works with "none" as the legend position, but "left", "top", "bottom", all fail with "Error in grid.Call.graphics("L_setviewport", pvp, TRUE) : Non-finite location and/or size for viewport" library(ggplot2) (myDat <- data.frame(cbind(VarX=10:1, VarY=runif(10)), Descrip=sample(LETTERS[1:3], 10, replace=TRUE))) qplot(VarX,VarY, data=myDat, shape=Descrip) + opts(legend.position="right") What am I doing wrong? Re-positioning a legend must be incredibly common, so I figure it's me.

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• How to move or position a legend in ggplot2

  - by Dan Goldstein

  I'm trying to create a ggplot2 plot with the legend beneath the plot. The ggplot2 book says on p 112 "The position and justification of legends are controlled by the theme setting legend.position, and the value can be right, left, top, bottom, none (no legend), or a numeric position". The following code works (since "right" it is the default), and it also works with "none" as the legend position, but "left", "top", "bottom", all fail with "Error in grid.Call.graphics("L_setviewport", pvp, TRUE) : Non-finite location and/or size for viewport" library(ggplot2) (myDat <- data.frame(cbind(VarX=10:1, VarY=runif(10)), Descrip=sample(LETTERS[1:3], 10, replace=TRUE))) qplot(VarX,VarY, data=myDat, shape=Descrip) + opts(legend.position="right") What am I doing wrong? Re-positioning a legend must be incredibly common, so I figure it's me.

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• a more pythonic way to express conditionally bounded loop?

  - by msw

  I've got a loop that wants to execute to exhaustion or until some user specified limit is reached. I've got a construct that looks bad yet I can't seem to find a more elegant way to express it; is there one? def ello_bruce(limit=None): for i in xrange(10**5): if predicate(i): if not limit is None: limit -= 1 if limit <= 0: break def predicate(i): # lengthy computation return True Holy nesting! There has to be a better way. For purposes of a working example, xrange is used where I normally have an iterator of finite but unknown length (and predicate sometimes returns False).

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• BackgroundWorker vs background Thread

  - by freddy smith

  I have a stylistic question about the choice of background thread implementation I should use on a windows form app. Currently I have a BackgroundWorker on a form that has an infinite (while(true)) loop. In this loop I use WaitHandle.WaitAny to keep the thread snoozing until something of interest happens. One of the event handles I wait on is a "stopthread" event so that I can break out of the loop. This event is signaled when from my overridden Form.Dispose(). I read somewhere that BackgroundWorker is really intended for operations that you dont want to tie up the UI with and have an finite end - like downloading a file, or processing a sequence of items. In this case the "end" is unknown and only when the window is closed. Therefore would it be more appropriate for me to use a background Thread instead of BackgroundWorker for this purpose?

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• Tiling solution for the iPhone that can handle infinite # of tiles

  - by rickharrison

  I have been looking at ways to implement a tiling solution on the iPhone/iPad similar to something like Google Maps. I have looked at examples of how to implement a CATiledLayer into a view that is inside a UIScrollView. Then when you scroll the view, the tiles request the new data to be shown. However, this seems to work when you have a finite view size (ie: 3000x3000). However, how could I work this into a tiling solution for much larger sizes. Basically, I want to be able to show data as needed for tiles as large as I can. Can I somehow use CATiledLayer to do this? Any direction would be greatly appreciated.

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• Why would it be a bad idea to have database connection open between client requests?

  - by AspOnMyNet

  1) Book I’m reading argues that connections shouldn’t be opened between client requests, since they are a finite resource. I realize that max pool size can quickly be reached and thus any further attempts to open a connection will be queued until connection becomes available and for that reason it would be imperative that we release connection as soon as possible. But assuming all request will open connection to the same DB, then I’m not sure how having a connection open between two client requests would be any less efficient than having each request first acquiring a connection from connection pool and later returning that object to connection pool? 2) Book also recommends that when database code is encapsulated in a dedicated data access class, then method M opening a database connection should also close that connection. a) I assume one reason why M should also close it, is because if method M opening the connection doesn’t also close it, but instead this connection object is used inside several methods, then it’s more likely that a programmer will forget to close it. b) Are there any other reasons why a method opening the connection should also close it? thanx

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• Drawing reflexive edges in State Machines

  - by reforged

  I have to draw a small finite state machine that has some reflexive transitions (meaning the start and the end state of the transition are equal. The problem is that rendering that in Graphviz has ugly results. digraph finite_state_machine { edge [fontsize=11]; S0 - S0 [label = "td=1\n-/e2"]; S0 - S1 [label = "td=3 \n-/e3" ]; S1 - S0 [label = "td=3\n-/-\nt=0"]; S0 - S2 [label = "P:i1/e4"]; S2 - S0 [label = "td=0\n-/-" ]; S0 - S0 [label = "i1/e1\ntd+=1"]; } Is there a way to make this look a little better? BTW: I tried head/tailport but they don't work on my version of Graphviz (1.13 on Mac OS X) I am not limited to the dot engine, I only want a nice looking graph and don't care about the renderer/language. Thanks a lot

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• Is there any way to limit the size of an STL Map?

  - by Nathan Fellman

  I want to implement some sort of lookup table in C++ that will act as a cache. It is meant to emulate a piece of hardware I'm simulating. The keys are non-integer, so I'm guessing a hash is in order. I have no intention of inventing the wheel so I intend to use stl::map for this (though suggestions for alternatives are welcome). The question is, is there any way to limit the size of the hash to emulate the fact that my hardware is of finite size? I'd expect the hash's insert method to return an error message or throw an exception if the limit is reached. If there is no such way, I'll simply check its size before trying to insert, but that seems like an inelegant way to do it.

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• Ruby on Rails questionnaire tutorial?

  - by kovrik

  Can't find any tutorial for creating a simple questionnaire system on RoR (without using Finite State Machines). I think the Model is simple: Quizzes (have many Questions) Questions (belong to Quizzes, have many Choices, have one Answer) Choices (belong to Questions) Responses (belong to Users, belong to Questions) Users (have many Responses). User logs in (session is created), chooses some Quiz (Questions which belong to this Quiz are shown). User navigates through the Questions, makes his choice (Response), finishes the Quiz. Responses are compared with Answers. System shows some results. But as I'm new to Rails it is difficult for me to make it work properly. Any help? Maybe there is a tutorial where some similar app is created?

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• language to create flowcharts

  - by robintw

  Hi, This seems like something which must have been answered before, but I can't find anything appropriate in the question archives. Basically, I'm looking for a little Domain Specific Language to create flowcharts. I'm terrible at graphic design and making things look nice, and I'd really like a langauge where I could write something in code and it would produce a pretty flowchart. I've come across GraphViz, but it seems more suited to creating things like Finite State Machine diagrams, rather than process flowcharts. It also doesn't have the simple DSL-style front-end that would allow me to easily work it. Any ideas? I'm sure this must have been done before... Robin

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• Synchronizing reading and writing with synchronous NamedPipes

  - by Mike Trader

  A Named Pipe Server is created with hPipe = CreateNamedPipe( zPipePath, PIPE_ACCESS_DUPLEX, PIPE_TYPE_BYTE | PIPE_WAIT | PIPE_READMODE_BYTE, PIPE_UNLIMITED_INSTANCES, 8192, 8192, NMPWAIT_USE_DEFAULT_WAIT, NULL) Then we immediately call: ConnectNamedPipe( hPipe, BYVAL %NULL ) Which blocks until the client connects. Then we proceed directly to ReadFile( hPipe, ... The problem is that it takes the Client takes a finite amount of time to prepare and write all the fcgi request parameters. This has usually not completed before the Pipe Server performs its ReadFile(). The Read file operation thus finds no data in the pipe and the process fails. Is there a mechanism to tell when a Write() has occurred/finished after a client has connected to a NamedPipe? If I had control of the Client process, I could use a common Mutex, but I don't, and I really do not want to get into I/O completion ports just to solve this problem! I can of course use a simple timer to wait 60m/s or so which is usually plenty of time for the wrote to complete, but that is a horrible hack.

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