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• Existentials and Scrap your Boilerplate

  - by finnsson

  I'm writing a XML (de)serializer using Text.XML.Light and Scrap your Boilerplate (at http://github.com/finnsson/Text.XML.Generic) and so far I got working code for "normal" ADTs but I'm stuck at deserializing existentials. I got the existential data type data DataBox where DataBox :: (Show d, Eq d, Data d) => d -> DataBox and I'm trying to get this to compile instance Data DataBox where gfoldl k z (DataBox d) = z DataBox `k` d gunfold k z c = k (z DataBox) -- not OK toConstr (DataBox d) = toConstr d dataTypeOf (DataBox d) = dataTypeOf d but I can't figure out how to implement gunfold for DataBox. The error message is Text/XML/Generic.hs:274:23: Ambiguous type variable `b' in the constraints: `Eq b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Show b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Data b' arising from a use of `k' at Text/XML/Generic.hs:274:18-30 Probable fix: add a type signature that fixes these type variable(s) It's complaining about not being able to figure out the data type of b. I'm also trying to implement dataCast1 and dataCast2 but I think I can live without them (i.e. an incorrect implementation). I guess my questions are: Is it possible to combine existentials with Scrap your Boilerplate? If so: how do you implement gunfold for an existential data type?

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• Error in bisection method code in Matlab

  - by Amanda Collins

  I need to write a proper implementation of the bisection method, which means I must address all possible user input errors. Here is my code: function [x_sol, f_at_x_sol, N_iterations] = bisection(f, xn, xp, eps_f, eps_x) % solving f(x)=0 with bisection method % f is the function handle to the desired function, % xn and xp are borders of search, % f(xn)<0 and f(xp)>0 required, % eps_f defines how close f(x) should be to zero, % eps_x defines uncertainty of solution x if(f(xp) < 0) error('xp must be positive') end; if(f(xn)>0) error('xn must be negative') end; if (xn >= xp) error ('xn must be less than xp') end; xg=(xp+xn)/2; %initial guess fg=f(xg); % initial function evaluation N_iterations=1; while ( (abs(fg) > eps_f) & (abs(xg-xp) > eps_x) ) if (fg>0) xp=xg; else xn=xg; end xg=(xp+xn)/2; %update guess fg=f(xg); %update function evaluation N_iterations=N_iterations+1; end x_sol=xg; %solution is ready f_at_x_sol=fg; if (f_at_x_sol > eps_f) error('No convergence') end and here is the error message I receive when I try to test this in Matlab: >> bisection(x.^2, 2, -1, 1e-8, 1e-10) Attempted to access f(-1); index must be a positive integer or logical. Error in bisection (line 9) if(f(xp)<0) I was attempting to see if my error codes worked, but it doesn't look like they do. I get the same error when I try to test it on a function that should work.

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• Tagging in Subversion - how do I make the decision about continuing to work on my trunk vs. the new

  - by Howiecamp

  I'm running Tortoise SVN to manage a project. Obviously the principles around tagging apply to any implementation of SVN but in this question I'll be referring to some TortoiseSVN-specific dialog boxes and messages. My working directory and the subversion repository structure both have a Source root directory and the Trunk, Tags and Branches directories underneath. (I couldn't figure out how to do a multilevel indented hierarchy in markdown without using bullets, so if someone could edit and fix this I'd appreciate it.) I'm working out of the Trunk directory in my working copy and it's pointing at the Trunk directory in the repo. I want to apply a Tag "Release1" so I click the "Branch/tag..." menu option and set the repo path as my [repo_path/bla/Source/Tags/Release1" tag. This dialog box gives me the option to "Switch my working copy to new branch/tag". I understand that if this option is left unchecked, the new "Release1" branch under /Tags" will be created but my working copy will remain on the previous "Trunk" path. If I do check this option (or use the Switch command) I understand that my working copy will switch to the new "Release1" branch under "/Tags". Where I'm missing a concept is how to make this decision. It doesn't seem like I want to switch my working directory to the recently created tag since by definition (?) I want that tag to be a snapshot of my code as of a point in time. If I don't switch the working directory, I'll continue working off Trunk and when I'm ready to take another snapshot I'll make another tag. And so on... Am I understanding this right or am I stating something incorrectly in the previous paragraph (e.g. the statement about not wanting to switch to the tag since the tag should represent a point in time snapshot) or otherwise missing something regarding how to make this decision?

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• Should a developer be a coauthor to a paper presented about the application they developed?

  - by ved

  In our organization, project teams come up with a need and funding and developers are given a basic scope and are allowed to develop the solution. There is a certain degree of implementation freedom given to the developers. They drive the solution to pilot and live deployment from its inception. If the solution is presented in a conference as a technical paper/white paper what is the protocol for the list of authors: because for the most part I see the project manager's and the dev team manager's names as authors but no mention of the actual developer. Is this correct? A lot of us developers feel pretty bummed to never see our names as the coauthors. Appreciate any pointers. Answers to the FOLLOW UP questions (1) in what field of study is the paper, and what are the standards of authorship for that field? The paper is for Flood Plain Management - there is nothing on the abstract guidelines, I have called the contact person listed for comment - waiting to hear. 2) was the paper literally about the software application as your question implies, or were the software issues incidental to the topic of the paper? The paper specifically deals with a GIS Application that is used in Coastal Engineering, yes the software is not incidental, but the meat of the paper and mentioned in the Title. 2

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• Prove correctness of unit test

  - by Timo Willemsen

  I'm creating a graph framework for learning purposes. I'm using a TDD approach, so I'm writing a lot of unit tests. However, I'm still figuring out how to prove the correctness of my unit tests For example, I have this class (not including the implementation, and I have simplified it) public class SimpleGraph(){ //Returns true on success public boolean addEdge(Vertex v1, Vertex v2) { ... } //Returns true on sucess public boolean addVertex(Vertex v1) { ... } } I also have created this unit tests @Test public void SimpleGraph_addVertex_noSelfLoopsAllowed(){ SimpleGraph g = new SimpleGraph(); Vertex v1 = new Vertex('Vertex 1'); actual = g.addVertex(v1); boolean expected = false; boolean actual = g.addEdge(v1,v1); Assert.assertEquals(expected,actual); } Okay, awesome it works. There is only one crux here, I have proved that the functions work for this case only. However, in my graph theory courses, all I'm doing is proving theorems mathematically (induction, contradiction etc. etc.). So I was wondering is there a way I can prove my unit tests mathematically for correctness? So is there a good practice for this. So we're testing the unit for correctness, instead of testing it for one certain outcome.

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• Are there any downsides in using C++ for network daemons?

  - by badcat

  Hey guys! I've been writing a number of network daemons in different languages over the past years, and now I'm about to start a new project which requires a new custom implementation of a properitary network protocol. The said protocol is pretty simple - some basic JSON formatted messages which are transmitted in some basic frame wrapping to have clients know that a message arrived completely and is ready to be parsed. The daemon will need to handle a number of connections (about 200 at the same time) and do some management of them and pass messages along, like in a chat room. In the past I've been using mostly C++ to write my daemons. Often with the Qt4 framework (the network parts, not the GUI parts!), because that's what I also used for the rest of the projects and it was simple to do and very portable. This usually worked just fine, and I didn't have much trouble. Being a Linux administrator for a good while now, I noticed that most of the network daemons in the wild are written in plain C (of course some are written in other languages, too, but I get the feeling that 80% of the daemons are written in plain C). Now I wonder why that is. Is this due to a pure historic UNIX background (like KISS) or for plain portability or reduction of bloat? What are the reasons to not use C++ or any "higher level" languages for things like daemons? Thanks in advance! Update 1: For me using C++ usually is more convenient because of the fact that I have objects which have getter and setter methods and such. Plain C's "context" objects can be a real pain at some point - especially when you are used to object oriented programming. Yes, I'm aware that C++ is a superset of C, and that C code is basically C++. But that's not the point. ;)

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• UIImagePickerController crashes on rapid scrolling, slower than photos app

  - by vvanhee

  Most of the time, my image picker works perfectly (iOS 4.2.1). However, if I scroll very rapidly up and down about 4-6 times through my camera roll of about 300 photos, I get a crash. This never happens with the "photos" app on the same iPhone 3Gs. Also, I'm noticing that the stock "photos" app scrolls much more smoothly than my image picker. Has anyone else noticed this behavior? I'd be interested if others could attempt this in their own apps and see if they crash. I don't think it's related to other objects hogging memory on my iPhone because it's a simple app, and this happens right after I start the app. It also doesn't seem to be related to messages sent to other released objects or overreleasing of other objects in viewdidunload, based on my crash logs and the fact that the simulator responds well to simulated memory warnings. I think it might be a bug in the internal implementation of the UIImagePickerController... This is how I start the picker. I've done this multiple ways (including setting a retain property for the UIImagePickerController in my header and releasing on dealloc). This seems to be the best way (crashes least): UIImagePickerController *picker = [[UIImagePickerController alloc] init]; picker.delegate = self; picker.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum; picker.allowsEditing = YES; [self presentModalViewController:picker animated:YES]; [picker release]; This is the crashed thread (I get various exception types): Exception Type: SIGSEGV Exception Codes: SEGV_ACCERR at 0xfffffffff4faafa4 Crashed Thread: 8 ... Thread 8 Crashed: 0 CoreFoundation 0x000494ea -[__NSArrayM replaceObjectAtIndex:withObject:] + 98 1 PhotoLibrary 0x00008e0f -[PLImageTable _segmentAtIndex:] + 527 2 PhotoLibrary 0x00008a21 -[PLImageTable _mappedImageDataAtIndex:] + 221 3 PhotoLibrary 0x0000893f -[PLImageTable dataForEntryAtIndex:] + 15 4 PhotoLibrary 0x000087e7 PLThumbnailManagerImageDataAtIndex + 35 5 PhotoLibrary 0x00008413 -[PLThumbnailManager _dataForPhoto:format:width:height:bytesPerRow:dataWidth:dataHeight:imageDataOffset:imageDataFormat:preheat:] + 299 6 PhotoLibrary 0x000b6c13 __-[PLThumbnailManager preheatImageDataForImages:withFormat:]_block_invoke_1 + 159 7 libSystem.B.dylib 0x000d6680 _dispatch_call_block_and_release + 20 8 libSystem.B.dylib 0x000d6ba0 _dispatch_worker_thread2 + 128 9 libSystem.B.dylib 0x0007b251 _pthread_wqthread + 265

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• Putting all methods in class definition

  - by Amnon

  When I use the pimpl idiom, is it a good idea to put all the methods definitions inside the class definition? For example: // in A.h class A { class impl; boost::scoped_ptr<impl> pimpl; public: A(); int foo(); } // in A.cpp class A::impl { // method defined in class int foo() { return 42; } // as opposed to only declaring the method, and defining elsewhere: float bar(); }; A::A() : pimpl(new impl) { } int A::foo() { return pimpl->foo(); } As far as I know, the only problems with putting a method definition inside a class definition is that (1) the implementation is visible in files that include the class definition, and (2) the compiler may make the method inline. These are not problems in this case since the class is defined in a private file, and inlining has no effect since the methods are called in only one place. The advantage of putting the definition inside the class is that you don't have to repeat the method signature. So, is this OK? Are there any other issues to be aware of?

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• Credit Card storage solution

  - by jtnire

  Hi Everyone, I'm developing a solution that is designed to store membership details, as well as credit card details. I'm trying to comply with PCI DSS as much as I can. Here is my design so far: PAN = Primary account number == long number on credit card Server A is a remote server. It stores all membership details (Names, Address etc..) and provides indivudal Key A's for each PAN stored Server B is a local server, and actually holds the encrypted PANs, as well as Key B, and does the decryption. To get a PAN, the client has to authenticate with BOTH servers, ask Server A for the respective Key A, then give Key A to server B, which will return the PAN to the client (provided authentication was sucessful). Server A will only ever encrypt Key A with Server B's public Key, as it will have it beforehand. Server B will probably have to send a salt first though, however I doin't think that has to be encrypted I havn't really thought about any implementation (i.e. coding) specifics yet regarding the above, however the solution is using Java's Cajo framework (wrapper for RMI) so that is how the servers will communicate with each other (Currently, membership details are transfered in this way). The reason why I want Server B to do the decryption, and not the client, is that I am afraid of decryption keys going into the client's RAM, even though it's probably just as bad on the server... Can anyone see anything wrong with the above design? It doesn't matter if the above has to be changed. Thanks jtnire

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• App Crashes Loading View Controllers

  - by golfromeo

  I have the following code in my AppDelegate.h file: @class mainViewController; @class AboutViewController; @interface iSearchAppDelegate : NSObject <UIApplicationDelegate> { UIWindow *window; mainViewController *viewController; AboutViewController *aboutController; UINavigationController *nav; } @property (nonatomic, retain) IBOutlet UIWindow *window; @property (nonatomic, retain) IBOutlet mainViewController *viewController; @property (nonatomic, retain) IBOutlet AboutViewController *aboutController; @property (nonatomic, retain) IBOutlet UINavigationController *nav; [...IBActions declared here...] @end Then, in my .m file: @implementation iSearchAppDelegate @synthesize window; @synthesize viewController, aboutController, settingsData, nav, engines; (void)applicationDidFinishLaunching:(UIApplication *)application { [window addSubview:nav.view]; [window addSubview:aboutController.view]; [window addSubview:viewController.view]; [window makeKeyAndVisible]; } -(IBAction)switchToHome{ [window bringSubviewToFront:viewController.view]; } -(IBAction)switchToSettings{ [window bringSubviewToFront:nav.view]; } -(IBAction)switchToAbout{ [window bringSubviewToFront:aboutController.view]; } - (void)dealloc { [viewController release]; [aboutController release]; [nav release]; [window release]; [super dealloc]; } @end Somehow, when I run the app, the main view presents itself fine... however, when I try to execute the actions to switch views, the app crashes with an EXC_BAD_ACCESS. Thanks for any help in advance.

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• How to store and remove dynamically and automatic variable of generic data type in custum list data

  - by Vineel Kumar Reddy

  Hi I have created a List data structure implementation for generic data type with each node declared as following. struct Node { void *data; .... .... } So each node in my list will have pointer to the actual data(generic could be anything) item that should be stored in the list. I have following signature for adding a node to the list AddNode(struct List *list, void* eledata); the problem is when i want to remove a node i want to free even the data block pointed by *data pointer inside the node structure that is going to be freed. at first freeing of datablock seems to be straight forward free(data) // forget about the syntax..... But if data is pointing to a block created by malloc then the above call is fine....and we can free that block using free function int *x = (int*) malloc(sizeof(int)); *x = 10; AddNode(list,(void*)x); // x can be freed as it was created using malloc what if a node is created as following int x = 10; AddNode(list,(void*)&x); // x cannot be freed as it was not created using malloc Here we cannot call free on variable x!!!! How do i know or implement the functionality for both dynamically allocated variables and static ones....that are passed to my list.... Thanks in advance...

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• FDs not closed in FUSE filesystem

  - by cor

  Hi, I have a problem while implementing a fuse filesystem in python. for now i just have a proxy filesystem, exactly like a mount --bind would be. But, any file created, opened, or read on my filesystem is not released (the corresponding FD is not closed) Here is an example : yume% ./ProxyFs.py `pwd`/test yume% cd test yume% ls mdr yume% echo test test yume% ls mdr test yume% ps auxwww | grep python cor 22822 0.0 0.0 43596 4696 ? Ssl 12:57 0:00 python ./ProxyFs.py /home/cor/esl/proxyfs/test cor 22873 0.0 0.0 6352 812 pts/1 S+ 12:58 0:00 grep python yume% ls -l /proc/22822/fd total 0 lrwx------ 1 cor cor 64 2010-05-27 12:58 0 - /dev/null lrwx------ 1 cor cor 64 2010-05-27 12:58 1 - /dev/null lrwx------ 1 cor cor 64 2010-05-27 12:58 2 - /dev/null lrwx------ 1 cor cor 64 2010-05-27 12:58 3 - /dev/fuse l-wx------ 1 cor cor 64 2010-05-27 12:58 4 - /home/cor/test/test yume% Does anyone have a solution to actually really close the fds of the file I use in my fs ? I'm pretty sure it's a mistake in the implementation of the open, read, write hooks but i'm stucked... Let me know if you need more details ! Thanks a lot Cor

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• PHP package manager

  - by Mathias

  Hey, does anyone know a package manager library for PHP (as e.g. apt or yum for linux distros) apart from PEAR? I'm working on a system which should include a package management system for module management. I managed to get a working solution using PEAR, but using the PEAR client for anything else than managing a PEAR installation is not really the optimal solution as it's not designed for that. I would have to modify/extend it (e.g. to implement actions on installation/upgrade or to move PEAR specific files like lockfiles away from the system root) and especially the CLI client code is quite messy and PHP4. So maybe someone has some suggestions for an alternative PEAR client library which is easy to use and extend (the server side has some nice implementations like Pirum and pearhub) for completely different package management systems written in PHP (ideally including dependency tracking and different channels) for some general ideas how to implement such a PM system (yes, I'm still tinkering with the idea of implementing such a system from scratch) I know that big systems like Magento and symfony use PEAR for their PM. Magento uses a hacked version of the original PEAR client (which I'd like to avoid), symfony's implementation seems quite integrated with the framework, but would be a good starting point to at least write the client from scratch. Anyway, if anybody has suggestions: please :)

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• Multi-Precision Arithmetic on MIPS

  - by Rob

  Hi, I am just trying to implement multi-precision arithmetic on native MIPS. Assume that one 64-bit integer is in register $12 and $13 and another is in registers $14 and $15. The sum is to be placed in registers $10 and $11. The most significant word of the 64-bit integer is found in the even-numbered registers, and the least significant word is found in the odd-numbered registers. On the internet, it said, this is the shortest possible implementation. addu $11, $13, $15 # add least significant word sltu $10, $11, $15 # set carry-in bit addu $10, $10, $12 # add in first most significant word addu $10, $10, $14 # add in second most significant word I just wanna double check that I understand correctly. The sltu checks if the sum of the two least significant words is smaller or equal than one of the operands. If this is the case, than did a carry occur, is this right? To check if there occured a carry when adding the two most significant words and store the result in $9 I have to do: sltu $9, $10, $12 # set carry-in bit Does this make any sense?

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• Boost's "cstdint" Usage

  - by patt0h

  Boost's C99 stdint implementation is awfully handy. One thing bugs me, though. They dump all of their typedefs into the boost namespace. This leaves me with three choices when using this facility: Use "using namespace boost" Use "using boost::[u]<type><width>_t" Explicitly refer to the target type with the boost:: prefix; e.g., boost::uint32_t foo = 0; Option ? 1 kind of defeats the point of namespaces. Even if used within local scope (e.g., within a function), things like function arguments still have to be prefixed like option ? 3. Option ? 2 is better, but there are a bunch of these types, so it can get noisy. Option ? 3 adds an extreme level of noise; the boost:: prefix is often = to the length of the type in question. My question is: What would be the most elegant way to bring all of these types into the global namespace? Should I just write a wrapper around boost/cstdint.hpp that utilizes option ? 2 and be done with it? Also, wrapping the header like so didn't work on VC++ 10 (problems with standard library headers): namespace Foo { #include <boost/cstdint.hpp> using namespace boost; } using namespace Foo; Even if it did work, I guess it would cause ambiguity problems with the ::boost namespace.

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• Looking for a RESTful or SOAP pipeline between WordPress and InterWoven TeamSite

  - by deanpeters

  I've been Googling my brains out trying see if there's a simple way to bridge content to and from WordPress to and from TeamSite. I'm coming at this from the perspective of a WordPress developer. I see in the book "The Definitive Guide to Interwoven TeamSite" (http://bit.ly/d3z4wI) mention of objects for the Interwoven LiveSite product: com.interwoven.livesite.external.impl.RSS com.interwoven.livesite.external.impl.SOAP If I understand the above objects correctly, these allow me to instantiate objects of these data types, which after populating them via various method calls, allow me to render content using com.interwoven.livesite.external.ExternalCall ... but I'm not sure. Nor do I think this approach provides me the 2-way street I seek. As it stands now, from my limited understanding, it appears that the least path of resistance is deploying Interwoven's LiveSite with the existing TeamSite implementation so content can be both consumed and rendered via RSS ... an channel which WordPress can produce and consume; the latter with plugins such as wp-o-matic and/or feedpress. So the question is, does anyone out there have experience with a SOAP or RESTful API approach to InterWoven's TeamSite? If so, can I get some direction on documentation? Or is the addition of LiveSite + RSS the most feasible 2-way channel?

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• Dynamically showing TableView or DetailView

  - by Niels

  From my TableView I dynamically want to show either a TableView or a DetailView (new segue), based on the cell's content. I setup two segues from the TableView to different DetailViews and one segue from the TableViewCell to the TableView. I have almost completed the implementation using performSegueWithIdentifier: (see below), but there is one struggling issue remaining: after I call [self dismissModalViewControllerAnimated:YES]; on the DetailView it returns to an empty TableView . I assume because the Storyboard segue from the UITableViewCell is performed. By clicking the back button I return to my original (parent) TableView data. Any suggestions for this work? - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { NSLog(@"%s", __PRETTY_FUNCTION__); NSString *type = [[self.dataController objectInListAtIndex:[self.tableView indexPathForSelectedRow].row] valueForKey:@"cell_type"]; NSLog(@"cell_type: %@", type); if([[segue identifier] isEqualToString:@"DetailSegue"]) { UIViewController *detailViewController = [segue destinationViewController]; detailViewController.game = [self.dataController objectInListAtIndex:[self.tableView indexPathForSelectedRow].row]; } else if ... } else if([[segue identifier] isEqualToString:@"TableViewSegue"]){ if([type isEqualToString:@"TableView"]){ //Create child ViewController, a custom ViewController with custom initWithId:Title: CategoryViewController *categoryViewController = [[segue destinationViewController] initWithId:categoryId Title:categoryTitle]; } } }

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• Performance improvement of client server system

  - by Tanuj

  I have a legacy client server system where the server maintains a record of some data stored in a sqlite database. The data is related to monitoring access patterns of files stored on the server. The client application is basically a remote viewer of the data. When the client is launched, it connects to the server and gets the data from the server to display in a grid view. The data gets updated in real time on the server and the view in the client automatically gets refreshed. There are two problems with the current implementation: When the database gets too big, it takes a lot of time to load the client. What are the best ways to deal with this. One option is to maintain a cache at the client side. How to best implement a cache ? How can the server maintain a diff so that it only sends the diff during the refresh cycle. There can be multiple clients and each client needs to display the latest data available on the server. The server is a windows service daemon. Both the client and the server are implemented in C#

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• Thread management advice - Is TPL a good idea?

  - by Ian

  I'm hoping to get some advice on the use of thread managment and hopefully the task parallel library, because I'm not sure I've been going down the correct route. Probably best is that I give an outline of what I'm trying to do. Given a Problem I need to generate a Solution using a heuristic based algorithm. I start of by calculating a base solution, this operation I don't think can be parallelised so we don't need to worry about. Once the inital solution has been generated, I want to trigger n threads, which attempt to find a better solution. These threads need to do a couple of things: They need to be initalized with a different 'optimization metric'. In other words they are attempting to optimize different things, with a precedence level set within code. This means they all run slightly different calculation engines. I'm not sure if I can do this with the TPL.. If one of the threads finds a better solution that the currently best known solution (which needs to be shared across all threads) then it needs to update the best solution, and force a number of other threads to restart (again this depends on precedence levels of the optimization metrics). I may also wish to combine certain calculations across threads (e.g. keep a union of probabilities for a certain approach to the problem). This is probably more optional though. The whole system needs to be thread safe obviously and I want it to be running as fast as possible. I tried quite an implementation that involved managing my own threads and shutting them down etc, but it started getting quite complicated, and I'm now wondering if the TPL might be better. I'm wondering if anyone can offer any general guidance? Thanks...

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• CompositionHost.Initialize() can not execute twice.

  - by Khoa

  I am currently try to integrate MEF and PRISM to work with each other. Everything is working fine so far. Now i would like to use MEF runtime module discovery (DeploymentCatalog) which will be used to download XAPs from server directory and then plug it into one of the Region inside my MAIN UI. I am using UnityBootStrapper and inside this class i also integrated MEF container. This sample application is based on Glenn Block (http://codebetter.com/glennblock/2010/01/03/mef-and-prism-exploration-mef-module-loading/). The following code is used to initialize CompositionContainer inside my Bootstrapper: // This is the host catalog which contains all parts of running assembly. var catalog = GetHostCatalog(); // Create MEF container which initial catalog var container = new CompositionContainer(catalog); // here we explicitly map a part to make it available on imports elsewhere, using // Unity to resolve the export so dependencies are resolved // We do this because region manager is third-party ... therefore, we need to // export explicitly because the implementation doesn't have its own [export] tag container.ComposeExportedValue<IRegionManager>(Container.Resolve<IRegionManager>()); container.ComposeExportedValue<IEventAggregator>(Container.Resolve<IEventAggregator>()); // Obtain CatalogService as a singleton // All dynamic modules will use this service to add its parts. Container.RegisterInstance<ICatalogService>(new CatalogService(catalog)); // Initialize the container CompositionHost.Initialize(container); Now i have another class called DeploymentCatalogService which is used to download the XAP from server. The current problem i am facing is that inside DeploymentCatalogService Initialize method, CompositionHost container is try to initialize its container with aggregateCatalog again. _aggregateCatalog = new AggregateCatalog(); _aggregateCatalog.Catalogs.Add(new DeploymentCatalog()); CompositionHost.Initialize(_aggregateCatalog); This causes an Exception which stated that The container has already been initialized. Is there a way to use the existing container and update it with the new aggregateCatalog? Hope this is not too confusing. Please be nice i am still new to MEF. Cheers,

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• Detect a USB drive being inserted - Windows Service

  - by Tom Bell

  I am trying to detect a USB disk drive being inserted within a Windows Service, I have done this as a normal Windows application. The problem is the following code doesn't work for volumes. Registering the device notification: DEV_BROADCAST_DEVICEINTERFACE notificationFilter; HDEVNOTIFY hDeviceNotify = NULL; ::ZeroMemory(&notificationFilter, sizeof(notificationFilter)); notificationFilter.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE); notificationFilter.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE; notificationFilter.dbcc_classguid = ::GUID_DEVINTERFACE_VOLUME; hDeviceNotify = ::RegisterDeviceNotification(g_serviceStatusHandle, &notificationFilter, DEVICE_NOTIFY_SERVICE_HANDLE); The code from the ServiceControlHandlerEx function: case SERVICE_CONTROL_DEVICEEVENT: PDEV_BROADCAST_HDR pBroadcastHdr = (PDEV_BROADCAST_HDR)lpEventData; switch (dwEventType) { case DBT_DEVICEARRIVAL: ::MessageBox(NULL, "A Device has been plugged in.", "Pounce", MB_OK | MB_ICONINFORMATION); switch (pBroadcastHdr->dbch_devicetype) { case DBT_DEVTYP_DEVICEINTERFACE: PDEV_BROADCAST_DEVICEINTERFACE pDevInt = (PDEV_BROADCAST_DEVICEINTERFACE)pBroadcastHdr; if (::IsEqualGUID(pDevInt->dbcc_classguid, GUID_DEVINTERFACE_VOLUME)) { PDEV_BROADCAST_VOLUME pVol = (PDEV_BROADCAST_VOLUME)pDevInt; char szMsg[80]; char cDriveLetter = ::GetDriveLetter(pVol->dbcv_unitmask); ::wsprintfA(szMsg, "USB disk drive with the drive letter '%c:' has been inserted.", cDriveLetter); ::MessageBoxA(NULL, szMsg, "Pounce", MB_OK | MB_ICONINFORMATION); } } return NO_ERROR; } In a Windows application I am able to get the DBT_DEVTYP_VOLUME in dbch_devicetype, however this isn't present in a Windows Service implementation. Has anyone seen or heard of a solution to this problem, without the obvious, rewrite as a Windows application?

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• With C# 3.0, how to write Interface based code with generic collection?

  - by Deecay

  I want to write code that is decouple and clean, and I know that by programming to an interface instead of the implementation, my code will be more flexible and extensible. So, instead of writing methods like: bool IsProductAvailable(ProductTypeA product); I write methods like: bool IsProductAvailable(IProduct product); As long as my products implement IProduct: class ProductTypeA : IProduct I should be OK. All is well until I start using generic collections. Since C# 3.0 doesn't support covariant and contravariant, even though both ProuctTypeA and ProductTypeB implements IProduct, you cannot put List in List. This is pretty troublesome because a lot of times I want to write something like: bool AreProductsAvailable(List<IProduct> products); So that I can check product avaialbility by writing: List<ProductA> productsArrived = GetDataFromDataabase(); bool result = AreProductsAvailable(productsArrived); And I want to write just one AreProductsAvailable() method that works with all IProduct collections. I know that C# 4.0 is going to support covariant and contravariant, but I also realize that there other libraries that seemed to have the problem solved. For instance, I was trying out ILOG Gantt the gantt chart control, and found that they have a lot of collection intefaces that looks like this: IActivityCollection ILinkCollection So it seems like their approach is wrapping the generic collection with an interface. So instead of "bool AreProductsAvailable(List products);", I can do: bool AreProductsAvailable(IProductCollection products); And then write some code so that IProductCollection takes whatever generic collection of IProduct, be it List or List. However, I don't know how to write an IProductCollection interface that does that "magic". :-< (ashame) .... Could someone shed me some light? This has been bugging me for so long, and I so wanted to do the "right thing". Well, thanks!

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• Convert C function to Objective C or alternative way to include C library?

  - by Moshe

  Background: I'm new to Objective-C and I've never touched C before. I'm trying to include a C library in my iPhone/iPod Touch project and I could not successfully compile the library's source code using the included instructions, so I've resorted to including the .h and .c files in Xcode. The library is for Hebrew Dates and corresponding Jewish Holidays. It can be found here: http://sourceforge.net/projects/libhdate/ I cannot seem to import the .c files into my implementation files. I can import the .h files though. When I try to use #import "file.c", where file.c is a file that is in XCode, it doesn't work. Why not? I've considered just writing the functions over in Objective-C, albeit only my needed functions and not the whole library. How can I make the following C function work in Objective-C? Are there other things that need to be included/re-coded/compiled? How so? I am almost certain something is missing, but I'm not sure what. Code: int hdate_get_omer_day(hdate_struct const * h) { int omer_day; hdate_struct sixteen_nissan; hdate_set_hdate(&sixteen_nissan, 16, 7, h->hd_year); omer_day = h->hd_jd - sixteen_nissan.hd_jd + 1; if ((omer_day > 49) || (omer_day < 0)) omer_day = 0; return omer_day; } So... should I be converting it, or trying somehow to compile to an appropriate format and how so? (I don't know what format a static library should be in, by the way, or if it should be static... - I'm so lost here....) I appreciate the help!

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• How does one gets started with Winforms style applications on Win32?

  - by Billy ONeal

  EDIT: I'm extremely tired and frustrated at the moment -- please ignore that bit in this question -- I'll edit it in the morning to be better. Okay -- a bit of background: I'm a C++ programmer mostly, but the only GUI stuff I've ever done was on top of .NET's WinForms platform. I'm completely new to Windows GUI programming, and despite Petzold's excellent book, I'm extremely confused. Namely, it seems that most every reference on getting started with Win32 is all about drawing lines and curves and things -- a topic about which (at least at present time) I couldn't care less. I need a checked list box, a splitter, and a textbox -- something that would take less than 10 minutes to do in Winforms land. It has been recommended to me to use the WTL library, which provides an implementation of all three of these controls -- but I keep getting hung up on simple things, such as getting the damn controls to use the right font, and getting High DPI working correctly. I've spent two freaking days on this, and I can't help but think there has to be a better reference for these kinds of things than I've been able to find. Petzold's book is good, but it hasn't been updated since Windows 95 days, and there's been a LOT changed w.r.t. how applications should be correctly developed since it was published. I guess what I'm looking for is a modern Petzold book. Where can I find such a resource, if any?

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• Very very weird problem with UIImageView property - I can access it then I can't, and it's not nil.

  - by just_another_coder

  Very very weird problem with UIImageView property on iPad application @interface MyViewController : UIViewController { IBOutlet UIImageView* coverImage; } @property(nonatomic, retain) IBOutlet UIImageView* coverImage; … more code @implementation MyViewController @synthesize coverImage; … more code - (void)viewDidLoad { [super viewDidLoad]; NSString* imageName = @"my_image.png"; UIImage* tempImage = [UIImage imageNamed:imageName]; [self.coverImage setImage:tempImage]; } The above code WILL display the image. In another part of code: -(IBAction) stopButtonPressed:(id)sender { [self.coverImage setHidden:YES]; NSLog(@"coverImage desc: %@", [coverImage description]); } The image will NOT disappear. I know the reference to the image isn't nil, because it gives me this output: 2010-05-29 17:37:40.706 MyApp[95360:207] coverImage desc: UIImageView: 0x5128420; frame = (0 0; 1024 768); autoresize = RM+BM; userInteractionEnabled = NO; layer = CALayer: 0x512bed0 In addition, if I move the code in viewDidLoad to another part of the class, and try to execute it from there, it fails to show the image at all.

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