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• Invalidating UITableView contents

  - by Roman

  I have an application with several UITableViewControllers. Now, the user is allowed to change "Data source". In that case I need to invalidate (reset) data in the relevant UITableViews. I figured out, that I can use NSNotificationCenter and add these controllers as observers to events which will be generated when the data source changes. The question is, how do I reset the underlying tables? I can, of course, set some boolean flag, and call UITableView:reloadData in viewWillAppear or viewDidAppear, but I was wondering, if there's a cleaner way of doing it. Or perhaps I'm completely missing the point, and I don't need NSNotificationCenter altogether. Thank you very much in advance.

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• Access static constant variable from multiple threads in C

  - by user325519

  I have some experience with multithread programming under Linux (C/C++ & POSIX threads), however most obvious cases are sometimes very complicated. I have several static constant variables (global and function local) in my code, can I access them simultaneously from multiple threads without using mutexes? Because I don't modify them it should be ok, but it's always better to ask. I have to do heavy speed optimization, so even as fast operations as mutex lock/unlock are quite expensive for me, especially because my application is going to access these variables form long loops.

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• python parallel computing: split keyspace to give each node a range to work on

  - by MatToufoutu

  My question is rather complicated for me to explain, as i'm not really good at maths, but i'll try to be as clear as possible. I'm trying to code a cluster in python, which will generate words given a charset (i.e. with lowercase: aaaa, aaab, aaac, ..., zzzz) and make various operations on them. I'm searching how to calculate, given the charset and the number of nodes, what range each node should work on (i.e.: node1: aaaa-azzz, node2: baaa-czzz, node3: daaa-ezzz, ...). Is it possible to make an algorithm that could compute this, and if it is, how could i implement this in python? I really don't know how to do that, so any help would be much appreciated

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• IDL-like parser that turns a document definition into powerful classes?

  - by paniq

  I am looking for an IDL-like (or whatever) translator which turns a DOM- or JSON-like document definition into classes which are accessible from both C++ and Python, within the same application expose document properties as ints, floats, strings, binary blobs and compounds: array, string dict (both nestable) (basically the JSON type feature set) allow changes to be tracked to refresh views of an editing UI provide a change history to enable undo/redo operations can be serialized to and from JSON (can also be some kind of binary format) allow to keep large data chunks on disk, with parts only loaded on demand provide non-blocking thread-safe read/write access to exchange data with realtime threads allow multiple editors in different processes (or even on different machines) to view and modify the document The thing that comes closest so far is the Blender 2.5 DNA/RNA system, but it's not available as a separate library, and badly documented. I'm most of all trying to make sure that such a lib does not exist yet, so I know my time is not wasted when I start to design and write such a thing. It's supposed to provide a great foundation to write editing UI components.

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• Reranging a uitableview

  - by Nicolay

  Hallo @ All I ran into the same problem as desciped in http://stackoverflow.com/questions/1884491/crashing-while-trying-to-move-uitableview-rows! All I want to do is on specific reranging operations insert a new cell or delet the selected one! Sometimes I get a * Assertion failure in -[_UITableViewUpdateSupport _setupAnimationForReorderingRow], /SourceCache/UIKit/UIKit-963.10/UITableViewSupport.m:295 Attempt to create two animations for cell exception and when I want to reload my data by calling [self.tableView reloadData] I get a * Terminating app due to uncaught exception 'NSRangeException', reason: '* -[NSCFArray objectAtIndex:]: index (0) beyond bounds (0)' This is quiet anoying! Is there anybody out there who knows how to handle this problem? Please help me!

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• Simple integer encryption

  - by tloflin

  Is there a simple algorithm to encrypt integers? That is, a function E(i,k) that accepts an n-bit integer and a key (of any type) and produces another, unrelated n-bit integer that, when fed into a second function D(i,k) (along with the key) produces the original integer? Obviously there are some simple reversible operations you can perform, but they all seem to produce clearly related outputs (e.g. consecutive inputs lead to consecutive outputs). Also, of course, there are cryptographically strong standard algorithms, but they don't produce small enough outputs (e.g. 32-bit). I know any 32-bit cryptography can be brute-forced, but I'm not looking for something cryptographically strong, just something that looks random. Theoretically speaking it should be possible; after all, I could just create a dictionary by randomly pairing every integer. But I was hoping for something a little less memory-intensive.

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• JavaScript pack("d") - binary strings

  - by Tim Whitlock

  I'm trying to replicate the Perl and PHP style pack and unpack functions in JavaScript. Unsigned integers were easy enough, so my pack('n') and pack('N') are ok. But my lack of a computer science background is a hurdle now and I don't know where to start with pack('d') for packing JavaScript's standard floating point. Is there a JavaScript library for this out there? If not, is there a good resource where I can learn how to do this? I am fine with bitwise and binary level operations in JS, I just don't know where to start with the logic. Thanks.

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• Long key press handling in android 1.5

  - by Kaillash

  Hi, I want to handle key press and long key press for the key code KEYCODE_BACK(back button). can any one suggest me how to do this in android 1.5(API level 3). Here is the code. public boolean onKeyDown(int keyCode, KeyEvent event) { if (keyCode == KeyEvent.KEYCODE_BACK) { if(event.getRepeatCount()==0) { // normal key press // But problem is, this code is hitting for long press also, how to avoid this } else { // Long key press //Do something here } // Always consume back key event by returning true //so that default behavior of back is overrided return true; } return super.onKeyDown(keyCode, event); }

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• Combining XSLT transforms

  - by Flynn1179

  Is there a way to combine two XSLT documents into a single XSLT document that does the same as transforming using the original two in sequence? i.e. Combining XSLTA and XSLTB into XSLTC such that XSLTB( XSLTA( xml )) == XSLTC( xml )? There's three reasons I'd like to be able to do this: Simplifies development; some operations need sequential transforms, and although I can generate a combined one by hand, it's a lot more difficult to maintain that two much simpler, separate transforms. Speed; one transform is in most cases hopefully faster than two. I'm currently working on a program that literally just transforms a data file in XML into an XHTML page capable of editing it using one XSLT, and a second XSLT that transforms the XHTML page back into the data file when it's saved. One test I hope to be able to do is to combine the two, and easily confirm that the 'combined' XSLT should leave the data unchanged.

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• cleartool question

  - by chuanose

  Lets say I have a directory at \testfolder, and the latest is currently at /main/10. I know that the operation resulting in testfolder@@/main/6 is to remove a file named test.txt. What's a sequence of cleartool operations that can be done in a script that will take "testfolder@@/main/6" and "test.txt" as input, and will cat out the contents of test.txt as of that time? One way I can think of is to get the time of /main/6 operation, create a view with config spec -time set to that time, and then cat the test.txt at the directory. But I'm wondering if I can do this in a easier way that doesn't involve manipulating config specs, perhaps through "cleartool find" and extended path names

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• A window that behaves both modally and non-modally

  - by Chris

  I want to create a WPF window that behaves as a modal dialogue box while at the same time facilitating selected operations on certain other windows of the same application. An example of this behaviour can be seen in Adobe Photoshop, which offers several dialogues that allow the user to use an eyedropper tool to make selections from an image while disabling virtually all other application features. I'm guessing that the way forward is to create a non-modal, always-on-top dialogue and programmatically disable those application features that are not applicable to the dialogue. Is there an easy way to achieve this in WPF? Or perhaps there's a design pattern I could adopt.

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• How to safely remove a USB drive on Windows CE 5.0?

  - by Radu C

  Until today, I assumed that Windows CE was writing everything to disk and I wouldn't end up with a broken FAT16 when I removed the USB stick. Today, I was proven wrong. I use a USB stick to test things on a WinCE 5.0 device. I don't write anything from the app or WinCE to the stick. I just execute my app, and my app reads its settings and pictures from the stick. Today, just this order of operations broke my stick filesystem (and I have to fix it). Is there a way to tell WinCE 5.0 to unmount the stick before I remove it? It sees it as a "Hard Drive", and the tap-and-hold menu has nothing along the lines of "safely remove drive". I'm happy with both code to do this operation and some trick that I didn't find in Windows CE yet. Thank you.

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• Promoting letters in a string to the next letter in java

  - by CSD1988

  I'm having issues figuring out how to get my code to increment the string that is given by user input so that when a user chooses to replace a letter like z it would go to a, b to c ect. The catch is I have to do this without using boolean. I am supposed to get this by using arithmetics to get the promotion from z to a from the users input. Plus must be only lower case letters from a-z. Any help would be appreciated thanks.

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• JAVA bytecode optimization

  - by Idob

  This is a basic question. I have code which shouldn't run on metadata beans. All metadata beans are located under metadata package. Now, I use reflection API to find out whether a class is located in the the metadata package. if (newEntity.getClass().getPackage().getName().contains("metadata")) I use this If in several places within this code. The question is: Should I do this once with: boolean isMetadata = false if (newEntity.getClass().getPackage().getName().contains("metadata")) { isMetadata = true; } C++ makes optimizations and knows that this code was already called and it won't call it again. Does JAVA makes optimization? I know reflection API is a beat heavy and I prefer not to lose expensive runtime.

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• JAVA: How do I accept input during a certain period of time only

  - by sebrock

  Im trying to do a simple game where I continually need input from players. This needs to happen during a certain time period only. Everything that is sent after that will be discarded. After the time period a new game starts. So: Start game Wait for input from all players during 10 seconds 10 secs no more input Calculate the winner and do some stuff Goto 1. I was thinking using a timer and timertask to keep track of time and maybe use a boolean variable that changes from "open" to "closed" after 10 seconds? Please give me some advise on this.

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• How to optimize indexing of large number of DB records using Zend_Lucene and Zend_Paginator

  - by jdichev

  So I have this cron script that is deployed and ran using Cron on a host and indexes all the records in a database table - the index is later used both for the front end of the site and the backed operations as well. After the operation, the index is about 3-4 MB. The problem is it takes a lot of resources (CPU: 30+ and a good chunk of memory) and slows the machine down. My question is about how to optimize the operation described below: First there is a select query built using the Zend Framework API, this query is then passed to a Paginator factory that returns a paginator which I am using to balance the current number of items being indexed and not iterate over too much items. The script is iterating over the current items in the paginator object using a foreach loop until reaching the end and then it starts from the beginning after getting items for the next page. I am suspecting this overhead is caused by the Zend_Lucene but no idea how this could be improved.

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• it is possible to "group by" without losing the original rows?

  - by toPeerOrNotToPeer

  i have a query like this: ID | name | commentsCount 1 | mysql for dummies | 33 2 | mysql beginners guide | 22 SELECT ..., commentsCount // will return 33 for first row, 22 for second one FROM mycontents WHERE name LIKE "%mysql%" also i want to know the total of comments, of all rows: SELECT ..., SUM(commentsCount) AS commentsCountAggregate // should return 55 FROM mycontents WHERE name LIKE "%mysql%" but this one obviously returns a single row with the total. now i want to merge these two queries in one single only, because my actual query is very heavy to execute (it uses boolean full text search, substring offset search, and sadly lot more), then i don't want to execute it twice is there a way to get the total of comments without making the SELECT twice? !! custom functions are welcome !! also variable usage is welcome, i never used them...

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• Do I need to syncronize thread access to an int

  - by Martin Harris

  I've just written a method that is called by multiple threads simultaneously and I need to keep track of when all the threads have completed, the code uses this pattern: private void RunReport() { _reportsRunning++; try { //code to run the report } finally { _reportsRunning--; } } This is the only place within the code that _reportsRunning's value is changed, and the method takes about a second to run. Occasionally when I have more than six or so threads running reports together the final result for _reportsRunning can get down to -1, if I wrap the calls to _runningReports++ and _runningReports-- in a lock then the behaviour appears to be correct and consistant. So, to the question: When I was learning multithreading in C++ I was taught that you didn't need to synchronize calls to increment and decrement operations because they were always one assembly instruction and therefore it was impossible for the thread to be switched out mid-call. Was I taught correctly, and if so how come that doesn't hold true for C#?

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• Which is the 'correct' way to do this (if statement)

  - by frinkz

  I've got plenty of these lying around, and I'm wondering if I'm going to face any trouble - or performance problems. I have method A: MyClass monkey; ... if(monkey != null) { ... } Or method B: boolean hasMonkey; //This is set to TRUE when monkey is not null MyClass monkey; ... if(hasMonkey) { ... } On a functional level, they both do the same thing. Right now, I'm using method A. Is that a bad way of doing things? Which is going to perform better?

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• How to Parse 'Mathy' Stuff...

  - by Rob P.

  Please forgive my title, I really don't know how to phrase it better. This isn't a school assignment or anything, but I realize it's a mostly academic question. But, what I've been struggling to do is parse 'math' text and come up with an answer. For Example - I can figure out how to parse '5 + 5' or '3 * 5' - but I fail when I try to correctly chain operations together. (5 + 5) * 3 It's mostly just bugging me that I can't figure it out. If anyone can point me in a direction, I'd really appreciate it.

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• How do I determine darker or lighter color variant of a given color?

  - by Nidonocu

  Given a source color of any hue by the system or user, I'd like a simple algorithm I can use to work out a lighter or darker variants of the selected color. Similar to effects used on Windows Live Messenger for styling the user interface. Language is C# with .net 3.5. Responding to comment: Color format is (Alpha)RGB. With values as bytes or floats. Marking answer: For the context of my use (a few simple UI effects), the answer I'm marking as accepted is actually the most simple for this context. However, I've given up votes to the more complex and accurate answers too. Anyone doing more advanced color operations and finding this thread in future should definitely check those out. Thanks SO. :)

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• C# eval equivalent?

  - by Adhip Gupta

  I can do an eval("something()"); to execute the code dynamically in JavaScript. Is there a way for me to do the same thing in C#? What I am exactly trying to do is that I have an integer variable (say i) and I have multiple properties by the names: "Property1","Property2","Property3" etc. Now, I want to perform some operations on the " Propertyi " property depending on the value of i. This is really simple with Javascript. Is there any way to do this with C#? Edit: Oh, and I am using C# 2.0

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• finditem() doesn't find menu, stuck with NullPointerException

  - by fdansv

  I'm stuck while changing some properties on my options menu at onCreateOptionsMenu(). It seems like findItem() returns null, even though I'm pretty sure that the reference to the menu item is correct. My code looks as follows: @Override public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.activity_profile, menu); MenuItem leftie = menu.findItem(R.id.menu_profile); leftie.setIcon(R.drawable.ic_menu_mapmode); leftie.setTitle(R.string.back_map); leftie.setIntent(authIntent); return true; } I really don't know what can be wrong there. Thanks in advance :) EDIT: I forgot to include the actual problem.

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• @ExceptionHandler doesn't handle the thrown exceptions

  - by Javi

  Hello, I have a method in my controller which will handle the exceptions thrown by the application. So I have a method like this one. @Controller public class ExceptionController { @RequestMapping(value="/error") @ExceptionHandler(value={Exception.class, NullPointerException.class}) public String showError(Exception e, Model model){ return "tiles:error"; } } And to try I if it works I throw a NullPointerException in another method in other method controller: boolean a = true; if(a){ throw new NullPointerException(); } After the exception is thrown it is printed in the JSP, but it doesn't go throw my showError() method (I've set a breakpoint there and it never enters). showError() method will catch the exception and will show different error pages depending on the exception type (though now it always shows the same error page). If I go to the url /error it shows the error page so the showError() method is OK. I'm using Spring 3. What can be the problem? Thanks.

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• Special simple random number generator

  - by psihodelia

  How to create a function, which on every call generates a random integer number? This number must be most random as possible (according to uniform distribution). It is only allowed to use one static variable and at most 3 elementary steps, where each step consists of only one basic arithmetic operation of arity 1 or 2. Example: int myrandom(void){ static int x; x = some_step1; x = some_step2; x = some_step3; return x; } Basic arithmetic operations are +,-,%,and, not, xor, or, left shift, right shift, multiplication and division. Of course, no rand(), random() or similar staff is allowed.

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