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• Ajax data two-way data binding strategies?

  - by morgancodes

  I'd like to 1) Draw create form fields and populate them with data from javascript objects 2) Update those backing objects whenever the value of the form field changes Number 1 is easy. I have a few js template systems I've been using that work quite nicely. Number 2 may require a bit of thought. A quick google search on "ajax data binding" turned up a few systems which seem basically one-way. They're designed to update a UI based on backing js objects, but don't seem to address the question of how to update those backing objects when changes are made to the UI. Can anyone recommend any libraries which will do this for me? It's something I can write myself without too much trouble, but if this question has already been thought through, I'd rather not duplicate the work.

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• How to handle multiple openIDs for the same user

  - by Sinan

  For my site I am using a login system much like the one on SO. A user can login with his Facebook, Google (Gmail openID), Twitter account. This question is not about specific oAuth or openID implementations. The question is how to know if the same user logins with different providers. Let me give an example: Bobo comes to site logins to site by clicking on "Login with Facebook". Because this is his first visit we create an account for him. Later Bobo comes to the site. This time he clicks on "Login with Google". So how do I know if this is the same person so I can add this provider to his account instead of creating a new (and duplicate) account. Can I trust solely on email? What is the best way to handle this. How does SO do it? Any ideas?

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• Why does the rename() syscall prohibit moving a directory that I can't write to a different director

  - by Daniel Papasian

  I am trying to understand why this design decision was made with the rename() syscall in 4.2BSD. There's nothing I'm trying to solve here, just understand the rationale for the behavior itself. 4.2BSD saw the introduction of the rename() syscall for the purpose of allowing atomic renames/moves of files. From 4.3BSD-Reno/src/sys/ufs/ufs_vnops.c: /* * If ".." must be changed (ie the directory gets a new * parent) then the source directory must not be in the * directory heirarchy above the target, as this would * orphan everything below the source directory. Also * the user must have write permission in the source so * as to be able to change "..". We must repeat the call * to namei, as the parent directory is unlocked by the * call to checkpath(). */ if (oldparent != dp->i_number) newparent = dp->i_number; if (doingdirectory && newparent) { VOP_LOCK(fndp->ni_vp); error = ufs_access(fndp->ni_vp, VWRITE, tndp->ni_cred); VOP_UNLOCK(fndp->ni_vp); So clearly this check was added intentionally. My question is - why? Is this behavior supposed to be intuitive? The effect of this is that one cannot move a directory (located in a directory that one can write) that one cannot write to another directory that one can write to atomically. You can, however, create a new directory, move the links over (assuming one has read access to the directory), and then remove one's write bit on the directory. You just can't do so atomically. % cd /tmp % mkdir stackoverflow-question % cd stackoverflow-question % mkdir directory-1 % mkdir directory-2 % mkdir directory-1/directory-i-cant-write % echo "foo" > directory-1/directory-i-cant-write/contents % chmod 000 directory-1/directory-i-cant-write/contents % chmod 000 directory-1/directory-i-cant-write % mv directory-1/directory-i-cant-write directory-2 mv: rename directory-1/directory-i-cant-write to directory-2/directory-i-cant-write: Permission denied We now have a directory I can't write with contents I can't read that I can't move atomically. I can, however, achieve the same effect non-atomically by changing permissions, making the new directory, using ln to create the new links, and changing permissions. (Left as an exercise to the reader) . and .. are special cased already, so I don't particularly buy that it is intuitive that if I can't write a directory I can't "change .." which is what the source suggests. Is there any reason for this besides it being the perceived correct behavior by the author of the code? Is there anything bad that can happen if we let people atomically move directories (that they can't write) between directories that they can write?

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• Why better isolation level means better performance in SQL Server

  - by Oleg Zhylin

  When measuring performance on my query I came up with a dependency between isolation level and elapsed time that was surprising to me READUNCOMMITTED - 409024 READCOMMITTED - 368021 REPEATABLEREAD - 358019 SERIALIZABLE - 348019 Left column is table hint, and the right column is elapsed time in microseconds (sys.dm_exec_query_stats.total_elapsed_time). Why better isolation level gives better performance? This is a development machine and no concurrency whatsoever happens. I would expect READUNCOMMITTED to be the fasted due to less locking overhead. Update: I did measure this with DBCC DROPCLEANBUFFERS DBCC FREEPROCCACHE issued and Profiler confirms there're no cache hits happening. Update2: The query in question is an OLAP one and we need to run it as fast as possible. Closing the production server from outside world to get the computation done is not out of question if this gives performance benefits.

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• Difference in amplitude from the same source using FFT

  - by Anders

  Hi, I have a question regarding use of FFT. Using function getBand(int i) with Minim i can extract the amplitude of a specific frequency and do pretty maps of it. Works great. However, this is a more of a curiosity question. When i look at the values extracted from playing the same song two twice using the same frequency (so the amplitude should be identical) but i get very different values - why is this? 0.0,0.0,0.0,0.0,0.0,0.08706585,0.23708777,0.83046436,0.74603105,0.30447206 0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.08706585,0.4790409,0.9608221,0.83046436,0.74603105

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• How would one use Cocos2d to create a game like this.

  - by John Stewart

  http://itunes.apple.com/us/app/angry-birds/id343200656?mt=8&ign-mpt=uo%3D6 So I am getting started with this all game dev thing on iphone and I decided that I will start playing with Cocos2d as my starting engine. Now just so i have a goal in mind, I picked angry birds as my initial target of what sort of game play would I like to learn to build. This is not going to be a market release game. This is totally going to be learning purposes only. So to start off my question is: Would something like this be achievable using Cocos2d? How would I go about building the physics for this? How can one do a screen scroll like the way they do in cocos2d? (any example code would be great) This is just to start off. If you have any particular questions please do add to this question.

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• MS ACCESS: How can i count distinct value using access query?

  - by Sadat

  here is the current complex query given below. SELECT DISTINCT Evaluation.ETCode, Training.TTitle, Training.Tcomponent, Training.TImpliment_Partner, Training.TVenue, Training.TStartDate, Training.TEndDate, Evaluation.EDate, Answer.QCode, Answer.Answer, Count(Answer.Answer) AS [Count], Questions.SL, Questions.Question FROM ((Evaluation INNER JOIN Training ON Evaluation.ETCode=Training.TCode) INNER JOIN Answer ON Evaluation.ECode=Answer.ECode) INNER JOIN Questions ON Answer.QCode=Questions.QCode GROUP BY Evaluation.ETCode, Answer.QCode, Training.TTitle, Training.Tcomponent, Training.TImpliment_Partner, Training.Tvenue, Answer.Answer, Questions.Question, Training.TStartDate, Training.TEndDate, Evaluation.EDate, Questions.SL ORDER BY Answer.QCode, Answer.Answer; There is an another column Training.TCode. I need to count distinct Training.TCode, can anybody help me? If you need more information please let me know

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• Programatically creating OpenGLView in Cocoa

  - by name

  FIXED. Please delete this question.

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• Java: using endpoint to publish webservice to tomcat server

  - by Will

  hi all, i am creating a simple SOAP web service. i am to ensure that it runs on a tomcat web service. im trying to implement this with JAX-WS (see code) my question is: does the Endpoint.publish use the tomcat server to host this or is it a mini glassfish kind of server? should i be extending UnicastRemoveObject or something similiar instead? ideally it would be able to be packaged into a .WAR and dropped in the directory and just work. It doesn't seem to work with my installed tomcat server as is because it says the port is already in use. I'm using Ubuntu karmic with the tomcat6 package installed, it could also be my user doesnt have permissions to publish to the running tomcat on 8080 i hope this question is clear enough sample code: @WebService public class UserAttributes { public static void main(String[] args) { UserAttributes instance = new UserAttributes(); Endpoint.publish("http://localhost:8082/WebServices/userattributes", instance); } public string Hello() { return "Hello World"; } }

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• Test if single linked list is circular by traversing it only once

  - by user1589754

  I am a fresher and I was asked this question in a recent interview I gave. The question was --- By traversing each element of linked list just once find if the single linked list is circular at any point. To this I answered that we will store reference of each node while traversing the list in another linked list and for every node in the list being tested we will find if the reference exists in the list I am storing the references. The interviewer said that he needs a more optimized way to solve this problem. Can anyone please tell me what would be a more optimized method to solve this problem.

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• Does CodeIgniter have to load view in the final step?

  - by Peter

  I have a function function do_something() { // process $this->load->view('some_view', $data); exec('mv /path/to/folder1/*.mp3 /path/to/folder2/'); } My intention is to move files after outputting the view. But apparently it is done before rendering the view. My question is, does $this->load->view(); have to be the final step in a function? I did a little research, and seems like my question is similar to this topic. Correct?

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• LINQ-to-SQL vs stored procedures?

  - by scottmarlowe

  I took a look at the "Beginner's Guide to LINQ" post here on StackOverflow (http://stackoverflow.com/questions/8050/beginners-guide-to-linq), but had a follow-up question: We're about to ramp up a new project where nearly all of our database op's will be fairly simple data retrievals (there's another segment of the project which already writes the data). Most of our other projects up to this point make use of stored procedures for such things. However, I'd like to leverage LINQ-to-SQL if it makes more sense. So, the question is this: For simple data retrievals, which approach is better, LINQ-to-SQL or stored procs? Any specific pro's or con's? Thanks.

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• Available Coroutine Libraries in Java

  - by JUST MY correct OPINION

  I would like to do some stuff in Java that would be clearer if written using concurrent routines, but for which full-on threads are serious overkill. The answer, of course, is the use of coroutines, but there doesn't appear to be any coroutine support in the standard Java libraries and a quick Google on it brings up tantalising hints here or there, but nothing substantial. Here's what I've found so far: JSIM has a coroutine class, but it looks pretty heavyweight and conflates, seemingly, with threads at points. The point of this is to reduce the complexity of full-on threading, not to add to it. Further I'm not sure that the class can be extracted from the library and used independently. Xalan has a coroutine set class that does coroutine-like stuff, but again it's dubious if this can be meaningfully extracted from the overall library. It also looks like it's implemented as a tightly-controlled form of thread pool, not as actual coroutines. There's a Google Code project which looks like what I'm after, but if anything it looks more heavyweight than using threads would be. I'm basically nervous of something that requires software to dynamically change the JVM bytecode at runtime to do its work. This looks like overkill and like something that will cause more problems than coroutines would solve. Further it looks like it doesn't implement the whole coroutine concept. By my glance-over it gives a yield feature that just returns to the invoker. Proper coroutines allow yields to transfer control to any known coroutine directly. Basically this library, heavyweight and scary as it is, only gives you support for iterators, not fully-general coroutines. The promisingly-named Coroutine for Java fails because it's a platform-specific (obviously using JNI) solution. And that's about all I've found. I know about the native JVM support for coroutines in the Da Vinci Machine and I also know about the JNI continuations trick for doing this. These are not really good solutions for me, however, as I would not necessarily have control over which VM or platform my code would run on. (Indeed any bytecode manipulation system would suffer similar problems -- it would be best were this pure Java if possible. Runtime bytecode manipulation would restrict me from using this on Android, for example.) So does anybody have any pointers? Is this even possible? If not, will it be possible in Java 7? Edited to add: Just to ensure that confusion is contained, this is a related question to my other one, but not the same. This one is looking for an existing implementation in a bid to avoid reinventing the wheel unnecessarily. The other one is a question relating to how one would go about implementing coroutines in Java should this question prove unanswerable. The intent is to keep different questions on different threads.

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• SSIS Script Component Testing Strategy

  - by Paul Kohler

  This question is in respect to the script component specifically. I am aware of ssisUnit etc… With simple SSIS Scripts Components, it’s sufficient to let basic testing flesh out issues, however I am working with a script that has grown in complexity over time. To better test the functionality I am considering abstracting the script logic into a DLL that gets deployed with the package, and then use the custom component in the script. The advantage is that the function will be more testable etc but it’s one more deployment artefact that needs to be managed. My question is, does anyone know of a better way to test such an SSIS script in a more isolated manner than to run the whole package and examine the output?

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• Wicket : Can a Panel or Component react on a form submit without any boilerplate code?

  - by MRalwasser

  I am currently evaluating Wicket and I am trying to figure out how things work. I have a question regarding form submit and panels (or other components). Imagine a custom wicket panel which contains a text field, doing as-you-type validation using ajax. This panel is added to a form. How can the Panel react a form submit (let's say because javascript/ajax is unavailable)? I am currently only aware of one solution: calling a panel's method inside the Form onSubmit() method. But this seems not like a "reusable" approach here, because I have to add boilerplate code to every form's onSubmit() which contains the panel (and every developer which use the panel must know this). So here comes my question: Is there any way that a Panel/Component can "detect" a form submit in some way? Or is there any other solution beside this? Thank you.

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• Globbing with MinGW on Windows

  - by Neil Butterworth

  I have an application built with the MinGW C++ compiler that works something like grep - acommand looks something like this: myapp -e '.*' *.txt where the thing that comes after the -e switch is a regex, and the thing after that is file name pattern. It seems that MinGW automatically expands (globs in UNIX terms) the command line so my regex gets mangled. I can turn this behaviour off, I discovered, by setting the global variable _CRT_glob to zero. This will be fine for bash and other sensible shell users, as the shell will expand the file pattern. For MS cmd.exe users however, it looks like I will have to expand the file pattern myself. So my question - does anyone know of a globbing library (or facility in MinGW) to do partial command line expansion? I'm aware of the _setargv feature of the Windows CRT, but that expands the full command line. Please note I've seen this question, but it really does not address partial expansion.

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• Changing constraints on the fly

  - by GoinOff

  Hi, I have a dijit.form.NumberTextBox input field that starts out with these parms: new dijit.form.NumberTextBox({ id: din1, style: "width:60px", constraints: { places: 0, pattern: '######' } }, din1); Everything works great..My question is I would like to change 'places' and 'pattern' parms on the fly. So I wrote this to change 'places' and 'patterns' parms: var myFldObj = dijit.byId(din1); if (myFldObj) { var myConstObj = myFldObj.attr('constraints'); if (myConstObj) { myConstObj.places = 2; myConstObj.pattern = '#####.0'; } } So, after I show the form again, I'd expect the entry field to allow 2 decimal places but the form still acts like places=0 and pattern='######'. When I check the values of 'places' and 'pattern' I get what I'd expect (2 and #####.0). My question: Can you change these values on the fly?? OR Do you have to destroy the original dijit object and recreate with new parms?? Thx!!

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• Kohana v3, automatically escape illegal characters?

  - by Dom

  Quick question, does Kohana (version 3) automatically escape data that is passed into ORM::factory..... (and everywhere else that has to do with the database)? For example: $thread = ORM::factory('thread', $this->request->param('id')); Would the data passed in the second argument be auto-escaped before it goes in the SQL query or do I have to manually do it? Probably a stupid question and it's better to be safe than sorry, but yeah... I usually do manually escape the data, but I want to know if Kohana does this for me? Thanks

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• counting fields based on group in crystal report

  - by hatem gamil

  hi all i wana ask a question about crystal reporting in vs 2008 lets say i have a report with these data customer_ID Customer_Name Order_amoont Order_Date (#group1 VipCustomer) 1 xyz 3 1/1/2010 2 abc 4 2/2/2010 5 sds 21 3/12/2009 (#Group2 NormalCustomer) 3 tyt 2 3/3/2010 4 ha 4 21/3/2009 i want only to display records where Order_Date year is in 2010 only so i went to the section expert and i added a condintion in suppress formula Year(order_Date)=2010 and i get the result ,,the question is how to count how many vip customers ordered in 2010 only and how many normal customer order in 2010 only ,,then i want the total number of both type of customers to be displayed to have a report like that:: customer_ID Customer_Name Order_amoont Order_Date (#group1 VipCustomer) 1 xyz 3 1/1/2010 2 abc 4 2/2/2010 subtotal 2 (#Group2 NormalCustomer) 3 tyt 2 3/3/2010 subtotal 1 total 3 thnx

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• Opinion on "loop invariants", and are these frequently used in the industry?

  - by Michael Aaron Safyan

  I was thinking back to my freshman year at college (five years ago) when I took an exam to place-out of intro-level computer science. There was a question about loop invariants, and I was wondering if loop invariants are really necessary in this case or if the question was simply a bad example... the question was to write an iterative definition for a factorial function, and then to prove that the function was correct. The code that I provided for the factorial function was as follows: public static int factorial(int x) { if ( x < 0 ){ throw new IllegalArgumentException("Parameter must be = 0"); }else if ( x == 0 ){ return 1; }else{ int result = 1; for ( int i = 1; i <= x; i++ ){ result*=i; } return result; } } My own proof of correctness was a proof by cases, and in each I asserted that it was correct by definition (x! is undefined for negative values, 0! is 1, and x! is 1*2*3...*x for a positive value of x). The professor wanted me to prove the loop using a loop invariant; however, my argument was that it was correct "by definition", because the definition of "x!" for a positive integer x is "the product of the integers from 1... x", and the for-loop in the else clause is simply a literal translation of this definition. Is a loop invariant really needed as a proof of correctness in this case? How complicated must a loop be before a loop invariant (and proper initialization and termination conditions) become necessary for a proof of correctness? Additionally, I was wondering... how often are such formal proofs used in the industry? I have found that about half of my courses are very theoretical and proof-heavy and about half are very implementation and coding-heavy, without any formal or theoretical material. How much do these overlap in practice? If you do use proofs in the industry, when do you apply them (always, only if it's complicated, rarely, never)?

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• Counting Alphabetic Characters That Are Contained in an Array with C

  - by Craig

  Hello everyone, I am having trouble with a homework question that I've been working at for quite some time. I don't know exactly why the question is asking and need some clarification on that and also a push in the right direction. Here is the question: (2) Solve this problem using one single subscripted array of counters. The program uses an array of characters defined using the C initialization feature. The program counts the number of each of the alphabetic characters a to z (only lower case characters are counted) and prints a report (in a neat table) of the number of occurrences of each lower case character found. Only print the counts for the letters that occur at least once. That is do not print a count if it is zero. DO NOT use a switch statement in your solution. NOTE: if x is of type char, x-‘a’ is the difference between the ASCII codes for the character in x and the character ‘a’. For example if x holds the character ‘c’ then x-‘a’ has the value 2, while if x holds the character ‘d’, then x-‘a’ has the value 3. Provide test results using the following string: “This is an example of text for exercise (2).” And here is my source code so far: #include<stdio.h> int main() { char c[] = "This is an example of text for exercise (2)."; char d[26]; int i; int j = 0; int k; j = 0; //char s = 97; for(i = 0; i < sizeof(c); i++) { for(s = 'a'; s < 'z'; s++){ if( c[i] == s){ k++; printf("%c,%d\n", s, k); k = 0; } } } return 0; } As you can see, my current solution is a little anemic. Thanks for the help, and I know everyone on the net doesn't necessarily like helping with other people's homework. ;P

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• Getting ssh to execute a command in the background on target machine

  - by dagorym

  This is a follow-on question to the How do you use ssh in a shell script? question. If I want to execute a command on the remote machine that runs in the background on that machine, how do I get the ssh command to return? When I try to just include the ampersand (&) at the end of the command it just hangs. The exact form of the command looks like this: ssh user@target "cd /some/directory; program-to-execute &" Any ideas? One thing to note is that logins to the the target machine always produce a text banner and I have ssh keys set up so no password is required.

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• Maximum number of files one ext3 directory while still getting acceptable performance?

  - by knorv

  I have an application writing to an ext3 directory which over time has grown to roughly three million files. Needless to say, reading the file listing of this directory is unbearably slow. I don't blame ext3. The proper solution would have been to let the directory write to sub-directories such as ./a/b/c/abc.ext rather than just ./abc.ext. I'm changing to such a sub-directory structure and my question is simply: roughly how many files should I expect to store in one ext3 directory while still getting acceptable performance? Or in other words; assuming that I need to store three million files in the structure, how many levels deep should the ./a/b/c/abc.ext structure be? Obviously this is a question that cannot be answered exactly, but I'm looking for a ball park estimate.

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• Web Application Translation, methods and tools

  - by CiscoIPPhone

  I've developed a web application. It needs to be translated to languages other than English in the future, and ideally the translators shouldn't need to know HTML/JS/C++ to provide the translation. The server side of the web application is written in C++ and the majority of the localised text is in the HTML files. My question is: What approaches are there to translating web applications? - Are there any existing tools that would enable a translator who doesn't understand HTML to translate a site? Should I write an application that extracts the localised text from a html file and can re-substitute translated text? Do you just provide the html file to your translators to be localised? I'm aware the question isn't strictly programming related but the solution may involve programming and it may require some software engineering.

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• How to get length of char**?

  - by nunos

  Quick c question: How to know the length of a char* foo[]? Thanks.

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