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• Would relational calculus be Turing-complete if it allowed unsafe queries?

  - by Jason Baker

  My understanding about Codd's concept of "safe queries" was created to ensure that a query would always terminate. One of the key ability of a Turing machine is that it can work on infinite calculations (and thus isn't guaranteed to terminate). If the safe query restriction were removed, would relational calculus be Turing-complete since that means it doesn't have to terminate?

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• Integer overflow exploitable?

  - by wuntee

  Does anyone have a detailed explanation on how integers can be exploited? I have been reading a lot about the concept, and I understand what an it is, and I understand buffer overflows, but I dont understand how one could modify memory reliably, or in a way to modify application flow, by making an integer larger than its defined memory....

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• Hibernate tool to create basic mappings based on a mysql db

  - by Blankman

  Are there any tools that can look at a database, and generate the basic mapping files? It would be great if it could take a database, and create the actual model (java classes) with annotations, but not sure if that exists?

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• Zend Table Relationship Modeling with Composite Key

  - by emeraldjava

  I have a table with a composite primary key using four columns. mysql> describe leaguesummary; +------------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------------------+------------------+------+-----+---------+----------------+ | leagueid | int(10) unsigned | NO | PRI | NULL | auto_increment | | leaguetype | enum('I','T') | NO | PRI | NULL | | | leagueparticipantid | int(10) unsigned | NO | PRI | NULL | | | leaguestandard | int(10) unsigned | NO | | NULL | | | leaguedivision | varchar(5) | NO | PRI | NULL | | | leagueposition | int(10) unsigned | NO | | NULL | | I have the league object modelled as so (all plain enough mappings) <?php class Model_DbTable_League extends Zend_Db_Table_Abstract { protected $_name = 'league'; protected $_primary = 'id'; protected $_dependentTables = array('Model_DbTable_LeagueSummary'); And I've started like this on the new model class. I've mapped a simple reference map which returns all rows linked to the league id. // http://files.zend.com/help/Zend-Framework/zend.db.table.relationships.html // http://naneau.nl/2007/04/21/a-zend-framework-tutorial-part-one/ class Model_DbTable_LeagueSummary extends Zend_Db_Table_Abstract { protected $_name = "leaguesummary"; protected $_primary = array('leagueid', 'leaguetype','leagueparticipantid','leaguedivision'); protected $_referenceMap = array( 'Summary' => array( 'columns' => array('leagueid'), 'refTableClass' => 'Model_DbTable_League', 'refColumns' => array('id') ), ..... ); } ?> The simple case works when called from my controller public function listAction() { // action body $leagueTable = new Model_DbTable_League(); $this->view->leagues = $leagueTable->getLeagues(); $league = $leagueTable->getLeague(6); // work $summary = $league->findDependentRowset('Model_DbTable_LeagueSummary','Summary'); Zend_Debug::dump($summary,"",true); I'm not sure how i can define extra _referenceMap keys which will take extra contraint ket values. I would like to be able to define a set called 'MenA' in which the type and division values are hardcoded, and the league id is taken from the initial rowset. 'MenA' =>array( 'columns' => array('leagueid','leaguetype','leaguedivision'), 'refTableClass' => 'Model_DbTable_League', 'refColumns' => array("id","I","A") ) Is this style of mapping possible ie hardcoding the values into the 'refColumns'. The second crazy idea i had was to pass the variable values in as part of the third param of the findDependentRowset() method. $menA = $league->findDependentRowset('Model_DbTable_LeagueSummary','MenA',array("I","A")); Any suggestions on how I might use the Zend DB Table Relationship mapping correctly to do this would be appreciated. I'm not interested in the plain, old and ugly $db-select(a,b,c)-where(..) style solution.

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• Autocomplete server-side implementation

  - by toluju

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

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• Best forum solution for symfony

  - by Zoja

  I'm looking for a good solution to integrate a forum in a symfony application. Something like phpBB. I've seen the plugins to integrate just the user of phpBB with symfony but that's not enough, and mapping database tables is a lame aprouch. So if anybody knows a good working component of a forum that would go well with a symfony app then I would really apreciate it :) Thanks !

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• Oracle Database introduction and literature

  - by Marco Nätlitz

  Hi folks, got an new assignment covering Oracle databases. My problem now is that I am completely new to the Oracle system and never worked with it before. I need to develop a concept covering the installation and configuration of the server. Afterwards I need to migrate the old server to the new while ensuring date consistence. I just wanted to ask if you guys have some useful links for introduction and of course good literature / books on this topic? Thanks and cheers from Cologne Marco

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• AI opponent car logic in car race game.

  - by ashok patidar

  hello i want to develop AI car(opponent) in car race game what should be my direction to develop them with less complexity because i don't have any idea. because the player car is moving on the scrolling track plz suggest me should i have to use relative motion or way point concept but that should also be change on the scrolling track (i.e. player car movement)

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• Request is not generated fro m jsp page

  - by Hitesh Solanki

  Hiii.... I am developing small spring application. I have to store the details of the student information in the database. I have develop one simpleformcontroller. I have used netbeans + hibernate mapping + spring. when I submit the form, jsp page is redirect on the same page and control does not go to Formcontroller..

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• Is key 'chord' functionality provided by Win32/.net?

  - by John

  Several MS apps support the concept of chords, like "CTRL+X,Y" which means "holding down CTRL, press X, then Y". Is this a bespoke thing they (and other companies) implement, or is it built into any APIs? It would be nice to be able to set up event handlers or accelerators based on chords rather than write code to do it.

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• What is the difference between "someValuesFrom" and "allValuesFrom"?

  - by ahmed

  In descriptive logic, what is the difference between "someValuesFrom" and "allValuesFrom"? In other words, the difference between (limited existential quantification) and (value restriction). For example, consider this picture: I have used the photoshop because I can't write some symbols. Is there any way to simplify the concept of somevaluefrom and allvaluesfrom?

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• Conventions for modelling c programs.

  - by Hassan Syed

  I'm working with a source base written almost entirely in straight-c (nginx). It does, however, make use of rich high level programming techniques such as compile-time metaprogramming, and OOP - including run-time dispatch. I want to draw ER diagrams, UML class diagrams and UML sequence diagrams. However to have a clean mapping between the two, consistent conventions must be applied. So, I am hopping someone has some references to material that establishes or applies such conventions to similar style c-code.

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• Parse URLs of major video streaming sites and generate appropriate code for embedding.

  - by Markus Lux

  Posting a video on tumblr.com allows you to just paste the URL of the video on youtube, vimeo, whatever and tumblr automatically does the embedding for you. I assume that this would be nothing more than a mapping between an URL-regex and the belonging HTML construct for embedding the video. Or it is just parsing the response of the URL and getting the construct from there. Is there already any utility, preferably in Java, for doing this? If not, how would you do it?

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• Can anyone explain the difference between closure and anonymous functions?

  - by Stick it to THE MAN

  I am relatively new to Javascript. I understand the concept of anonymous functions - but closures seem less clear. The similarity between the two (in my mind atleast), is confusing. Could someone explain the difference? (preferrably, with some code snippet, to illustrate the points clearer).

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• Explaining abstraction to a non-programmer.

  - by Dominic Bou-Samra

  Abstraction is a concept that seems difficult to explain, without reverting to using programming terminology. I've thought about it a lot, and I can't come up with a satisfactory answer. Does anyone have any very general, yet very pertinent explanations? Metaphors, similes etc are all welcome.

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• Spring Security 3 - Login is not working

  - by newbie

  I use Spring Security with Spring Framework 3 and when I tyr to login from homepage I get following error: 2010-04-26 12:16:39,525 [tomcat-http--2] WARN org.springframework.web.servlet.PageNotFound - No mapping found for HTTP request with URI [/AppName/app/j_spring_security_check] in DispatcherServlet with name 'Spring MVC Dispatcher Servlet' Spring Security is initialized as loggings tell and there are no errors. So what could be reason for this error? I have understood that j_spring_security_check is default url for Spring Security login chekeing servlet.

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• Can lazy loading be considered an example of RAII?

  - by codemonkey

  I have been catching up on my c++ lately, after a couple years of exclusive Objective-C on iOS, and the topic that comes up most on 'new style' c++ is RAII To make sure I understand RAII concept correctly, would you consider Objective-C lazy loading property accessors a type of RAII? For example, check the following access method - (NSArray *)items { if(_items==nil) { _items=[[NSArray alloc] initWithCapacity:10]; } return _items } Would this be considered an example of RAII? If not, can you please explain where I'm mistaken?

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• Meaning of Primary Key to Microsoft SQL Server 2008

  - by usr

  What meaning does the concept of a primary key have to the database engine of SQL Server? I don't mean the clustered/nonclustered index created on the "ID" column, i mean the constraint object "primary key". Does it matter if it exists or not? Alternatives: alter table add primary key clustered alter table create clustered index Does it make a difference?

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• AI opponenet car logic in car race game.

  - by ashok patidar

  i am using way point for the artificial car but i don't know the exact concept for that i want to make 3 AI car so how can i mange them parameter based like acceleration speed rotation on turn and collision b/w them pl z guide me.

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• Disable Internet Explorer 8 Developer Tools

  - by Steve Brouillard

  Is there a way to either disable Internet Explorer 8 Developer Tools, or at least change the shortcut key mapping? I'm working on an ASP.NET AJAX app that has used the F12 key for a function for years (it's actually a hold over from the original DOS app). Customers have used this key for the sam function for nearly 15 years and we'd really like to avoid having to move that function. Cheers

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• Why "private" methods in the object oriented ?

  - by pointlesspolitics

  I understand it is a very basic concept in the oops. But still I cannot get my head around. I understood why member variables are private, so class user cannot abuse it by setting up invalid values. But how can this apply to the methods ?

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• linq groupby in strongly typed MVC View

  - by jason

  How do i get an IGrouping result to map to the view? I have this query: var groupedManuals = manuals.GroupBy(c => c.Series); return View(groupedManuals); What is the proper mapping for the ViewPage declaration? Inherits="System.Web.Mvc.ViewPage<IEnumerable<ProductManual>>"

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• AJAX in Rails - doing simple looping to update information when available

  - by Acidburn2k

  I am trying to get put out a simple site, which would pool the database every few seconds and update the information on the page dynamicly, when theres something new inserted. I am farily new to ruby, but I understand the whole concept of RJS, link_to_function and soforth. The question is, what is the best way how to implement some kind of simple loop, which would run after the page is loaded and update the DOM if there is something new to display. Thanks in advance for any tips!

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• Can nullptr be emulated in gcc?

  - by nuzz

  I saw that nullptr was implemented in Visual Studio 2010. I like the concept and want to start using it as soon as possible; however GCC does not support it yet. My code needs to run on both (but doesn't have to compile with other compilers). Is there a way to "emulate" it? Something like: #define nullptr NULL (but obviously that wouldn't work well at all, I was simply showing what I meant).

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• asp.net: Where can I put my source files.

  - by David Sykes

  I am developing a web form using Visual Web Developer Currently I have class source files in the same directory as the web form, or in the App_Code folder. I'd like to organise the files into folders within the web form folder, but I can't find a way of adding a reference to the folders, and they don't seem to be being picked up automatically. These are files that are under constant development. What is the asp.net/c#'s equivalent concept to c++'s #include?

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