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  • MySql "comments" parameter as descriptor?

    - by Nick
    So, I'm trying to learn a lot at once, and this place is really helpful! I'm making a little running log website for myself and maybe a few other people, and I have it so that the user can add workouts for each day. With each workout, I have a variety of information the user can fill out for the workout, such as running distance, time, quality of run, course, etc... I store this in a MySql database as a table with fields titled "distance", "time", "runquality", etc... Now, these field titles don't match up with what I want displayed on the running log, so I was thinking of using the "Comments" attribute for a field to store its human-readable title--thus the field "runquality" would have "Quality of run" as its comment, and then I would pull the comment with a SQL query and display it instead of the field name. Is this a good theoretical/practical way of going about it? And what sort of SQL would I use to pull the comment for the field anyway? Secondly, suppose I want to add the ability for the user to create their own workout descriptors. So say a user wants to add a "temperature" descriptor for their workout. Should I create a script that adds fields to my workout table, or should I create a separate table listing only workout descriptors and somehow link the descriptor table with the "contents" table? I haven't learned any theory about database design or anything so any help is appreciated!

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  • How would you start automating my job?

    - by Jurily
    At my new job, we sell imported stuff. In order to be able to sell said stuff, currently the following things need to happen for every incoming shipment: Invoice arrives, in the form of an email attachment, Excel spreadsheet Monkey opens invoice, copy-pastes the relevant part of three columns into the relevant parts of a spreadsheet template, where extremely complex calculations happen, like =B2*550 Monkey sends this new spreadsheet to boss (email if lucky, printer otherwise), who sets the retail price Monkey opens the reply, then proceeds to input the data into the production database using a client program that is unusable on so many levels it's not even worth detailing Monkey fires up HyperTerminal, types in "AT", disconnect Monkey sends text messages and emails to customers using another part of the horrible client program, one at a time I want to change Monkey from myself to software wherever possible. I've never written anything that interfaces with email, Excel, databases or SMS before, but I'd be more than happy to learn if it saves me from this. Here's my uneducated wishlist: Monkey asks Thunderbird (mail server perhaps?) for the attachment Monkey tells Excel to dump the spreadsheet into a more Jurily-friendly format, like CSV or something Monkey parses the output, does the complex calculations // TODO: find a way to get the boss-generated prices with minimal manual labor involved Monkey connects to the database, inserts data Monkey spams costumers Is all this feasible? If yes, where do I start reading? How would you improve it? What language/framework do you think would be ideal for this? What would you do about the boss?

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  • PEAR:DB connection parameters

    - by Markus Ossi
    I just finished my first PHP site and now I have a security-related question. I used PEAR:DB for the database connection and made a separate parameter file for it. How should I hide this parameter file? I found a guide (http://www.kitebird.com/articles/peardb.html) that says: Another way to specify connection parameters is to put them in a separate file that you reference from your main script. ... It also enables you to move the parameter file outside of the web server's document tree, which prevents its contents from being displayed literally if the server becomes misconfigured and starts serving PHP scripts as plain text. I have now put my file in a directory like this /include/db_parameters.inc However, if I go to this URL, the web server shows me the contents of the file including my database username and password. From what I've understood, I should protect this file so, that even though PHP would be served as text, nobody could read this. What does outside of web server's document tree mean here? Put the PHP file out of public_html directory altogether deeper into the server file system? Some CHMOD?

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  • Convert charset in mysql query

    - by Yousf
    Hi, I have a question about converting charset from inside mysql query. I have a 2 databases. One for the website (joomla), the other for forum (IPB). I am doing query from inside joomla, which by default have "SET NAMES UTF8". I want to query a table inside the forum databases. A table called "ibf_topics". This table has latin1 encoding. I do the following to select anything from the not-utf8 table. //convert connection to handle latin1. $query = "SET NAMES latin1"; $db->setQuery($query); $db->query(); $query = "select id, title from other_database.ibf_topics"; $db->setQuery($query); $db->query(); //read result into an array. //return connection to handle UTF8. $query = "SET NAMES UTF8"; $db->setQuery($query); $db->query(); After that, when I want to use the selected tile, I use the following: echo iconv("CP1256", "UTF-8", $topic['title']) The question is, is there anyway to avoid all this hassle? For now, I can't change forum database to UTF8 and I can't change joomla database to latin1 :S

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  • Complex Quary on cassandra

    - by Sadiqur Rahman
    I have heard on cassandra database engine few days ago and searching for a good documentation on it. after studying on cassandra I got cassandra is more scalable than other data engine. I also read on Amazon SimpleDB but as SimpleDB has a limitation 10GB/table and Google Datastore is slower than Amazon SimpleDB, I prefer not to use them (Google Datastore, Amazon SimpleDB). So for making our site scaled specially high write rates with massive data, I like to use Cassandra as out Data Engine. But before starting using cassandra I am confused on "How to handle complex data using casssandra". I am giving you the MySQL database structure below, Please read this and give me a good suggestion. Users Table hasColum ID Primary hasColum email Unique hasColum FirstName hasColum LastName Category Table hasColum ID Primary hasColum Parent hasColum Category Posts Table hasColum ID Primary hasColum UID Index foreign key linked to users-ID hasColum CID Index foreign key linked to Category-ID hasColum Title hasColum Post Index hasColum PunDate Comments hasColum ID primary hasColum UID Index foreign key linked to users-ID hasColum PID Index foreign key linked to Posts-ID hasColum Comment User Group hasColum ID primary hasColum Name UserToGroup Table (for many to many relation only) hasColum UID foreign key linked to Users-ID hasColum GID foreign key linked to Group-ID Finally for your information, I like to use SimpleCassie PHP Class http://code.google.com/p/simpletools-php/ So, it will be very helpful if you can give me example using SimpleCassie

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  • Modeling many-to-one with constraints?

    - by Greg Beech
    I'm attempting to create a database model for movie classifications, where each movie could have a single classification from each of one of multiple rating systems (e.g. BBFC, MPAA). This is the current design, with all implied PKs and FKs: TABLE Movie ( MovieId INT ) TABLE ClassificationSystem ( ClassificationSystemId TINYINT ) TABLE Classification ( ClassificationId INT, ClassificationSystemId TINYINT ) TABLE MovieClassification ( MovieId INT, ClassificationId INT, Advice NVARCHAR(250) -- description of why the classification was given ) The problem is with the MovieClassification table whose constraints would allow multiple classifications from the same system, whereas it should ideally only permit either zero or one classifications from a given system. Is there any reasonable way to restructure this so that a movie having exactly zero or one classifications from any given system is enforced by database constraints, given the following requirements? Do not duplicate information that could be looked up (i.e. duplicating ClassificationSystemId in the MovieClassification table is not a good solution because this could get out of sync with the value in the Classification table) Remain extensible to multiple classification systems (i.e. a new classification system does not require any changes to the table structure)? Note also the Advice column - each mapping of a movie to a classification needs to have a textual description of why that classification was given to that movie. Any design would need to support this.

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  • Have ASP page call save function anytime the user tries to navigate away from page

    - by Breander
    What I have is an input page with a bunch of dynamically created textboxes for the user to input data. The textboxes are dynamically created because the number that are needed are not known until the user selects some options on the page. So what I need to have happen is if the user tries to either A) navigate away from the page or B) select different options bringing up new textboxes. Anything the user may have typed into the textboxes needs to automatically be saved to the database. Like they clicked on the save button on the page. This doesn't sound like a vary smart way to do things or even an easy way to do things but this is the requirement I have been given. No message just save to the database. I have looked into things like onbeforepageunload javascript but that mostly tries to stop the user from navigating away I can't call any code behind code from it. Any help is appreciated. Note : The number of the texboxes with data can be any where between 20 and 500. Yes very crazy but not my idea.

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  • How to retrive user input data entered tab bar View Controller when application start in iphone app

    - by TechFusion
    Hello, I have created window based application. Tab bar controller as root controller and it has three tabs. One Tab has Labels and TextFiled inputs like Name, Username and Password. I am looking to store this text filed inputs when user enters and able retrieve in other tabs. Previously I have set key for different text fields and setobject:withkey task and able to retrive text filed values in same view Controller [[NSUserDefaults standardUserDefaults] stringForKey:key] task. Now I am looking to create database which has different objects and each objects has data values of different Text Field inputs that I can access in whole application. like DatabaseName - Object1 - Name, Username & Password - Object2 - Name, Username & Password Something like structure in Normal C so it would be easy to retrieve data. I am looking NSUserDefaults Class and User Defaults Programming Topics in Cocoa(http://developer.apple.com/iPhone/library/documentation/Cocoa/Conceptual/UserDefaults/UserDefaults.html#//apple_ref/doc/uid/10000059-BCIDJFHD). Also Referring Archives and Serialization Programming guide(http://developer.apple.com/iphone/library/documentation/Cocoa/Conceptual/Archiving/Archiving.html#//apple_ref/doc/uid/10000047i). Which method i need to use to create such type of database ? Thanks,

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  • Is there a way to create subdatabases as a kind of subfolders in sql server?

    - by user193655
    I am creating an application where there is main DB and where other data is stored in secondary databases. The secondary databases follow a "plugin" approach. I use SQL Server. A simple installation of the application will just have the mainDB, while as an option one can activate more "plug-ins" and for every plug-in there will be a new database. Now why I made this choice is because I have to work with an exisiting legacy system and this is the smartest thing I could figure to implement the plugin system. MainDB and Plugins DB have exactly the same schema (basically Plugins DB have some "special content", some important data that one can use as a kind of template - think to a letter template for example - in the application). Plugin DBs are so used in readonly mode, they are "repository of content". The "smart" thing is that the main application can also be used by "plugin writers", they just write a DB inserting content, and by making a backup of the database they creaetd a potential plugin (this is why all DBs has the same schema). Those plugins DB are downloaded from internet as there is a content upgrade available, every time the full PlugIn DB is destroyed and a new one with the same name is creaetd. This is for simplicity and even because the size of this DBs is generally small. Now this works, anyway I would prefer to organize the DBs in a kind of Tree structure, so that I can force the PlugIn DBs to be "sub-DBs" of the main application DB. As a workaround I am thinking of using naming rules, like: ApplicationDB (for the main application DB) ApplicationDB_PlugIn_N (for the N-th plugin DB) When I search for plugin 1 I try to connect to ApplicationDB_PlugIn_1, if I don't find the DB i raise an error. This situation can happen for example if som DBA renamed ApplicationDB_Plugin_1. So since those Plugin DBs are really dependant on ApplicationDB only I was trying to "do the subfolder trick". Can anyone suggest a way to do this? Can you comment on this self-made plugin approach I decribed above?

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  • how to print data in a table from mysql

    - by robertdd
    hello, i want to extract the last eight entries from my database and print them into a 2 columns table!like this: |1|2| |3|4| |5|6| |7|8| is that possible? this is my code: $db = new Database(DB_SERVER, DB_USER, DB_PASS, DB_DATABASE); $db->connect(); $sql = "SELECT ID, movieno FROM movies ORDER BY ID DESC LIMIT 8 "; $rows = $db->query($sql); print '<table width="307" border="0" cellspacing="5" cellpadding="4">'; while ($record = $db->fetch_array($rows)) { $vidaidi = $record['movieno']; print <<<END <tr> <td> <a href="http://www.youtube.com/watch?v=$vidaidi" target="_blank"> <img src="http://img.youtube.com/vi/$vidaidi/1.jpg" width="123" height="80"></a> </td> </tr> END; } print '</table>';

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  • Logic in the db for maintaining a points system relationship?

    - by MarcusBooster
    I'm making a little web based game and need to determine where to put logic that checks the integrity of some underlying data in the sql database. Each user keeps track of points assigned to him, and points are awarded by various tasks. I keep a record of each task transaction to make sure they're not repeated, and to keep track of the value of the task at the time of completion, since an individual award level my fluctuate over time. My schema looks like this so far: create table player ( player_ID serial primary key, player_Points int not null default 0 ); create table task ( task_ID serial primary key, task_PointsAwarded int not null ); create table task_list ( player_ID int references player(player_ID), task_ID int references task(task_ID), when_completed timestamp default current_timestamp, point_value int not null, --not fk because task value may change later constraint pk_player_task_id primary key (player_ID, task_ID) ); So, the player.player_Points should be the total of all his cumulative task points in the task_list. Now where do I put the logic to enforce this? Should I do away with player.player_Points altogether and do queries every time I want to know the total score? Which seems wasteful since I'll be doing that query a lot over the course of a game. Or, put a trigger in the task_list that automatically updates the player.player_Points? Is that too much logic to have in the database and should just maintain this relationship in the application? Thanks.

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  • SQL -- How is DISTINCT so fast without an index?

    - by Jonathan
    Hi, I have a database with a table called 'links' with 600 million rows in it in SQLite. There are 2 columns in the database - a "src" column and a "dest" column. At present there are no indices. There are a fair number of common values between src and dest, but also a fair number of duplicated rows. The first thing I'm trying to do is remove all the duplicate rows, and then perform some additional processing on the results, however I've been encountering some weird issues. Firstly, SELECT * FROM links WHERE src=434923 AND dest=5010182. Now this returns one result fairly quickly and then takes quite a long time to run as I assume it's performing a tablescan on the rest of the 600m rows. However, if I do SELECT DISTINCT * FROM links, then it immediately starts returning rows really quickly. The question is: how is this possible?? Surely for each row, the row must be compared against all of the other rows in the table, but this would require a tablescan of the remaining rows in the table which SHOULD takes ages! Any ideas why SELECT DISTINCT is so much quicker than a standard SELECT?

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  • How to store and synchronize a big list of strings

    - by Joel
    I have a large database table in SQLExpress on Windows, with a particular field of interest 'code'. I have an Apache web server with MySQL on Linux. The web application on the Linux box needs access to the list of all codes. The only thing it will use the list for is checking for the existence of a given code. Having the Linux server call out to the Windows server is impractical as the Windows server is behind a NAT'ed office internet connection, and it may not always be accessible. I have set it so the Windows server will push the list of codes to the web server by means of a simple HTTP POST request. However, at this point I have not implemented the storage of the codes on the Linux box. Should I store them in a MySQL table with a single field 'code'? Then I get fast indexed lookups O(1), however I think synchronization will be an issue - given an updated list of codes, pushed from the Windows box, how would I optimally synchronize the list with the database? TRUNCATE, followed by INSERT? Should I instead store them in a flat file? Then I have O(n) look up time rather than O(1). Additionally an extra constant-time overhead too, as I will be processing the file in Ruby. However, synchronization is easy - simply replace the file.

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  • find the difference between two very large list

    - by user157195
    I have two large list(could be a hundred million items), the source of each list can be either from a database table or a flat file. both lists are of comparable sizes, both unsorted. I need to find the difference between them. so I have 3 scenarios: 1. List1 is a database table(assume each row simply have one item(key) that is a string), List2 is a large file. 2. Both lists are from 2 db tables. 3. both lists are from two files. in case 2, I plan to use: select a.item from MyTable a where a.item not in (select b.item form MyTable b) this clearly is inefficient, is there a better way? Another approach is: I plan to sort each list, and then walk down both of them to find the diff. If the list is from a file, I have to read it into a db table first, then use db sorting to output the list. Is the run time complexity still O(nlogn) in db sorting? either approach is a pain and seems would be very slow when the list involved has hundreds of millions of items. any suggestions?

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  • Moving from wordpress.com to self-hosted wordpress blog

    - by Sarfraz
    Hello, I have been writing articles on the wordpress.com blog, now i am looking to move it to self-hosted wordpress blog but i wonder: 1) Should i move all my articles on the new blog or just put an article on my last blog that more articles will be posted on my new blog?* 2) If i move all articles on my new blog, i am not sure about how google will react to it because there are articles with good number of visitors, won't this be seo-un-friendly because i am not sure but google will re-create page reputation stuff, etc or those articles will have same popularity even if i move elsewhere?* 3) What are the implications and side-effects in moving from wordpress.com blog to self-hosted wordpress blog?* Thanks

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  • IE8 Developer Tools won't open

    - by Dave
    Just installed IE8 on WinXP. Trying to use the Dev Tools but, clicking on the menu item or hitting F12 doesn't do anything. I can see the option in the tools menu, just can't use it. I've checked to make sure it wasn't opening minimized or off screen and I've checked the registry settings used to disable them. Those registry keys don't even exists. Suggestions? I was going to reinstall, but, thought I'd check here first.

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  • Path Not Found error when opening VB6 project from a shared folder on Virtual PC 2007 (XP sp3)

    - by law1185
    I currently work on a small software team that primarily maintains legacy software. I am trying to set up a VirtualPC that we can use to do this maintenance. Specifically, I would like to be able to debug and run VB6 web apps from a folder on the host pc. My constraints are as follows: The VirtualPC will not be registered on the domain. The server that hosts our Subversion repository does not run the subversion service so the only way to interact with the repository is through "file:\\", which requires domain authentication. It is not possible to debug/run VB6 web apps that are located on mapped network drives, because IIS requires that the VirtualPC be on the same domain as the network drive I would like to avoid having to copy the folder from the host pc to the VirtualPC and then copying it back in order to have the latest revision from Subversion So, I am trying to use VirtualPC's shared folder feature to share the host machine's Subversion directory and open the project in VB6 on the VirtualPC. Problem is that Visual Basic throws the error: "Path not found: '\\C:\\Subversion\Path\Project.vbp'" when I try to open it. Folder C:\Subversion on the host machine is mapped to G: on the VirtualPC. If anyone can help me resolve this error or find some other way to accomplish this, I would be deeply grateful. Oh, both host and virtual OS is Windows XP sp3. Using VB 6.0, IIS v5.1. I can manipulate files in the shared directory freely from the VirtualPC ie. copy, paste, delete, etc. Edit: Link to screenshot: http://img190.imageshack.us/img190/5439/vpcscreen.png

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  • Box2d: Set active and inactive

    - by Rosarch
    I'm writing an XNA game in C# using the XNA port of Box2d - Box2dx. Entities like trees or zombies are represented as GameObjects. GameObjectManager adds and removes them from the game world: /// <summary> /// Does the work of removing the GameObject. /// </summary> /// <param name="controller">The GameObject to be removed.</param> private void removeGameObjectFromWorld(GameObjectController controller) { controllers.Remove(controller); worldState.Models.Remove(controller.Model); controller.Model.Body.SetActive(false); } public void addGameObjectToWorld(GameObjectController controller) { controllers.Add(controller); worldState.Models.Add(controller.Model); controller.Model.Body.SetActive(true); } controllers is a collection of GameObjectController instances. worldState.Models is a collection of GameObjectModel instances. When I remove GameObjects from Box2d this way, this method gets called: void IContactListener.EndContact(Contact contact) { GameObjectController collider1 = worldQueryUtils.gameObjectOfBody(contact.GetFixtureA().GetBody()); GameObjectController collider2 = worldQueryUtils.gameObjectOfBody(contact.GetFixtureB().GetBody()); collisionRecorder.removeCollision(collider1, collider2); } worldQueryUtils: // this could be cached if we know bodies never change public GameObjectController gameObjectOfBody(Body body) { return worldQueryEngine.GameObjectsForPredicate(x => x.Model.Body == body).Single(); } This method throws an error: System.InvalidOperationException was unhandled Message="Sequence contains no elements" Source="System.Core" StackTrace: at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source) at etc Why is this happening? What can I do to avoid it? This method has been called many times before the body.SetActive() was called. I feel that this may be messing it up.

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  • Extra blank page when converting HTML to PDF using abcPDF.

    - by ProfK
    I have an HTML report, with each print page contained by a <div class="page">. The page class is defined as width: 180mm; height: 250mm; page-break-after: always; background-position: centre top; background-image: url(Images/MainBanner.png); background-repeat: no-repeat; padding-top: 30mm; After making a few changes to my report content, when I call abcPDF to convert the report to PDF, suddenly I'm getting a blank page inserted after every real report page. I don't want to roll back the changes I've just made to remove this problem, so I'm hoping someone may know why the extra pages are being inserted.

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  • Unrecognized configuration section httpHandlers in Web.Config with Microsoft Visual Web Developer 20

    - by FatboyFudge
    Hi all, I am in need of some help with an error message I get with Microsoft Visual Web Developer 2010 Express. I would like to create a gallery for my site so I downloaded the NotesForGallery from codeplex. I have added the reference into the project like it told me to in the installation instructions. The instructions then say Register the ThumbnailHandler in the Web.Config file (httpHandlers section): <httpHandlers> … <add verb="*" path="ThumbnailHandler.ashx" type="NotesFor.ThumbnailHandler, NotesForGallery"/> … </httpHandlers> So I open the web.config file in my solution and I add it in. When I try and start the website (clicking the play button in Web Developer) I get the error message: Unrecognized configuration section httpHandlers. The complete list of errors I get are: Message 1 Could not find schema information for the element 'httpHandlers'. C:\Documents and Settings\adam\My Documents\Visual Studio 2010\WebSites\FatBoyFudge\Web.config 38 4 C:...\FatBoyFudge\ Message 2 Could not find schema information for the element 'add'. C:\Documents and Settings\adam\My Documents\Visual Studio 2010\WebSites\FatBoyFudge\Web.config 39 8 C:...\FatBoyFudge\ Message 3 Could not find schema information for the attribute 'verb'. C:\Documents and Settings\adam\My Documents\Visual Studio 2010\WebSites\FatBoyFudge\Web.config 39 12 C:...\FatBoyFudge\ Message 4 Could not find schema information for the attribute 'path'. C:\Documents and Settings\adam\My Documents\Visual Studio 2010\WebSites\FatBoyFudge\Web.config 39 21 C:...\FatBoyFudge\ Message 5 Could not find schema information for the attribute 'type'. C:\Documents and Settings\adam\My Documents\Visual Studio 2010\WebSites\FatBoyFudge\Web.config 39 50 C:...\FatBoyFudge\ Error 6 Unrecognized configuration section httpHandlers. C:\Documents and Settings\adam\My Documents\Visual Studio 2010\WebSites\FatBoyFudge\Web.config 38 Warning 7 C:\Documents and Settings\adam\My Documents\Visual Studio 2010\WebSites\FatBoyFudge\Gallery.aspx: ASP.NET runtime error: Unrecognized configuration section httpHandlers. (C:\Documents and Settings\adam\My Documents\Visual Studio 2010\WebSites\FatBoyFudge\web.config line 38) C:\Documents and Settings\adam\My Documents\Visual Studio 2010\WebSites\FatBoyFudge\Gallery.aspx 1 1 C:...\FatBoyFudge\ The project I created was a website if that helps any. The complete web.config is as follows: <configuration> <connectionStrings> <add name="ApplicationServices" connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\aspnetdb.mdf;User Instance=true" providerName="System.Data.SqlClient"/> </connectionStrings> <system.web> <compilation debug="true" targetFramework="4.0"/> <authentication mode="Forms"> <forms loginUrl="~/Account/Login.aspx" timeout="2880"/> </authentication> <membership> <providers> <clear/> <add name="AspNetSqlMembershipProvider" type="System.Web.Security.SqlMembershipProvider" connectionStringName="ApplicationServices" enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="false" requiresUniqueEmail="false" maxInvalidPasswordAttempts="5" minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0" passwordAttemptWindow="10" applicationName="/"/> </providers> </membership> <profile> <providers> <clear/> <add name="AspNetSqlProfileProvider" type="System.Web.Profile.SqlProfileProvider" connectionStringName="ApplicationServices" applicationName="/"/> </providers> </profile> <roleManager enabled="false"> <providers> <clear/> <add name="AspNetSqlRoleProvider" type="System.Web.Security.SqlRoleProvider" connectionStringName="ApplicationServices" applicationName="/"/> <add name="AspNetWindowsTokenRoleProvider" type="System.Web.Security.WindowsTokenRoleProvider" applicationName="/"/> </providers> </roleManager> </system.web> <system.webServer> <modules runAllManagedModulesForAllRequests="true"/> </system.webServer> <httpHandlers> <add verb="*" path="ThumbnailHandler.ashx" type="NotesFor.ThumbnailHandler, NotesForGallery"/> </httpHandlers> </configuration> Any help you could give me would be handy because I'm not sure what I am doing wrong

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  • Installing Paperclip - "undefined method `has_attached_file` for" - Ruby on Rails

    - by bgadoci
    I just installed the plugin for Paperclip and I am getting an error message "undefined method has_attached_file for. Not sure why I am getting this. Here is the full error message. NoMethodError (undefined method `has_attached_file' for #<Class:0x10338acd0>): /Users/bgadoci/.gem/ruby/1.8/gems/will_paginate-2.3.12/lib/will_paginate/finder.rb:170:in `method_missing' app/models/post.rb:2 app/controllers/posts_controller.rb:50:in `show' For some reason it is referencing the will_paginate gem. From what I can find, it seems that either there is something wrong w/ my PostsController#index or perhaps a previously attempt at installing the gem instead of the plugin (in which case I have read I should be able to remedy through the /config/environments.rb file somehow). I didn't think that previous gem installation would matter as I did it in an old version of the site that I trashed before installing the plugin. In the current version of the site I show that the Table has been updated with the Paperclip columns after migration. Here is my code: PostsController#index def index @tag_counts = Tag.count(:group => :tag_name, :order => 'count_all DESC', :limit => 20) conditions, joins = {}, :votes @vote_counts = Vote.count(:group => :post_title, :order => 'count_all DESC', :limit => 20) conditions, joins = {}, :votes unless(params[:tag_name] || "").empty? conditions = ["tags.tag_name = ? ", params[:tag_name]] joins = [:tags, :votes] end @posts=Post.paginate( :select => "posts.*, count(*) as vote_total", :joins => joins, :conditions=> conditions, :group => "votes.post_id", :order => "created_at DESC", :page => params[:page], :per_page => 5) @popular_posts=Post.paginate( :select => "posts.*, count(*) as vote_total", :joins => joins, :conditions=> conditions, :group => "votes.post_id", :order => "vote_total DESC", :page => params[:page], :per_page => 3) respond_to do |format| format.html # index.html.erb format.xml { render :xml => @posts } format.json { render :json => @posts } format.atom end end Post Model class Post < ActiveRecord::Base has_attached_file :photo validates_presence_of :body, :title has_many :comments, :dependent => :destroy has_many :tags, :dependent => :destroy has_many :votes, :dependent => :destroy belongs_to :user after_create :self_vote def self_vote # I am assuming you have a user_id field in `posts` and `votes` table. self.votes.create(:user => self.user) end cattr_reader :per_page @@per_page = 10 end /views/posts/new.html.erb <h1>New post</h1> <%= link_to 'Back', posts_path %> <% form_for(@post, :html => { :multipart => true}) do |f| %> <%= f.error_messages %> <p> <%= f.label :title %><br /> <%= f.text_field :title %> </p> <p> <%= f.label :body %><br /> <%= f.text_area :body %> </p> <p> <%= f.file_field :photo %> </p> <p> <%= f.submit 'Create' %> </p> <% end %>

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  • Runge-Kutta (RK4) integration for game physics

    - by Kai
    Gaffer on Games has a great article about using RK4 integration for better game physics. The implementation is straightforward but the math behind it confuses me. I understand derivatives and integrals on a conceptual level but I haven't manipulated equations in a long time. Here's the brunt of Gaffer's implementation: void integrate(State &state, float t, float dt) { Derivative a = evaluate(state, t, 0.0f, Derivative()); Derivative b = evaluate(state, t+dt*0.5f, dt*0.5f, a); Derivative c = evaluate(state, t+dt*0.5f, dt*0.5f, b); Derivative d = evaluate(state, t+dt, dt, c); const float dxdt = 1.0f/6.0f * (a.dx + 2.0f*(b.dx + c.dx) + d.dx); const float dvdt = 1.0f/6.0f * (a.dv + 2.0f*(b.dv + c.dv) + d.dv) state.x = state.x + dxdt * dt; state.v = state.v + dvdt * dt; } Can anybody explain in simple terms how RK4 works? Specifically, why are we averaging the derivatives at 0.0f, 0.5f, 0.5f, and 1.0f? How is averaging derivatives up to the 4th order different from doing a simple euler integration with a smaller timestep? After reading the accepted answer below, and several other articles, I have a grasp on how RK4 works. To answer my own questions: Can anybody explain in simple terms how RK4 works? RK4 takes advantage of the fact that we can get a much better approximation of a function if we use its higher-order derivatives rather than just the first or second derivative. That's why the Taylor series converges much faster than Euler approximations. (take a look at the animation on the right side of that page) Specifically, why are we averaging the derivatives at 0.0f, 0.5f, 0.5f, and 1.0f? The Runge-Kutta method is an approximation of a function that samples derivatives of several points within a timestep, unlike the Taylor series which only samples derivatives of a single point. After sampling these derivatives we need to know how to weigh each sample to get the closest approximation possible. An easy way to do this is to pick constants that coincide with the Taylor series, which is how the constants of a Runge-Kutta equation are determined. This article made it clearer for me: http://web.mit.edu/10.001/Web/Course%5FNotes/Differential%5FEquations%5FNotes/node5.html. Notice how (15) is the Taylor series expansion while (17) is the Runge-Kutta derivation. How is averaging derivatives up to the 4th order different from doing a simple euler integration with a smaller timestep? Mathematically it converges much faster than doing many Euler approximations. Of course, with enough Euler approximations we can gain equal accuracy to RK4, but the computational power needed doesn't justify using Euler.

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  • Xtragrid Devexpress SetRowcellValue

    - by Learner
    const int index = 1; object val = repositoryItemComboBox3.Items[index]; gridView2.SetRowCellValue(gridView2.FocusedRowHandle, object w= gridView2.GetRowCellValue(gridView2.FocusedRowHandle, "gridColumn3",val); but w does not gets updated what do I have to do more?

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