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• How do I create a python module from a fortran program with f2py?

  - by Lars Hellemo

  I am trying to read some smps files with python, and found a fortran implementation, so I thought I would give f2py a shot. The problem is that I have no experience with fortran. I have successfully installed gfortran and f2py on my Linux box and ran the example on thew f2py page, but I have some trouble compiling and running the large program. There are two files, one with a file reader wrapper and one with all the logic. They seem to call each other, but when I compile and link or try f2py, I get errors that they somehow can't find each other: f95 -c FILEWR~1.F f95 -c SMPSREAD.F90 f95 -o smpsread SMPSREAD.o FILEWR~1.o FILEWR~1.o In function `file_wrapper_' FILEWR~1.F(.text+0x3d) undefined reference to `chopen_' usrlibgcci486-linux-gnu4.4.1libgfortranbegin.a(fmain.o) In function `main' (.text+0x27) undefined reference to `MAIN__' collect2 ld returned 1 exit status I also tried changing the name to FILE_WRAPPER.F but that did not help. With f2py I found out I had to include a comment to get it to accept free format, and saved this as a new file and tried: f2py -c -m smpsread smpsread.f90 I get a lot of output and warnings, but the error seems to be this one: getctype: No C-type found in "{'typespec': 'type', 'attrspec': ['allocatable'], 'typename': 'node', 'dimension': [':']}", assuming void. The fortran 90 spms reader can be found here. Any help or suggestions appreciated.

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• Legitimate uses of the Function constructor

  - by Marcel Korpel

  As repeatedly said, it is considered bad practice to use the Function constructor (also see the ECMAScript Language Specification, 5th edition, § 15.3.2.1): new Function ([arg1[, arg2[, … argN]],] functionBody) (where all arguments are strings containing argument names and the last (or only) string contains the function body). To recapitulate, it is said to be slow, as explained by the Opera team: Each time […] the Function constructor is called on a string representing source code, the script engine must start the machinery that converts the source code to executable code. This is usually expensive for performance – easily a hundred times more expensive than a simple function call, for example. (Mark ‘Tarquin’ Wilton-Jones) Though it's not that bad, according to this post on MDC (I didn't test this myself using the current version of Firefox, though). Crockford adds that [t]he quoting conventions of the language make it very difficult to correctly express a function body as a string. In the string form, early error checking cannot be done. […] And it is wasteful of memory because each function requires its own independent implementation. Another difference is that a function defined by a Function constructor does not inherit any scope other than the global scope (which all functions inherit). (MDC) Apart from this, you have to be attentive to avoid injection of malicious code, when you create a new Function using dynamic contents. Lots of disadvantages and it is intelligible that ECMAScript 5 discourages the use of the Function constructor by throwing an exception when using it in strict mode (§ 13.1). That said, T.J. Crowder says in an answer that [t]here's almost never any need for the similar […] new Function(...), either, again except for some advanced edge cases. So, now I am wondering: what are these “advanced edge cases”? Are there legitimate uses of the Function constructor?

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• Generating lognormally distributed random number from mean, coeff of variation

  - by Richie Cotton

  Most functions for generating lognormally distributed random numbers take the mean and standard deviation of the associated normal distribution as parameters. My problem is that I only know the mean and the coefficient of variation of the lognormal distribution. It is reasonably straight forward to derive the parameters I need for the standard functions from what I have: If mu and sigma are the mean and standard deviation of the associated normal distribution, we know that coeffOfVar^2 = variance / mean^2 = (exp(sigma^2) - 1) * exp(2*mu + sigma^2) / exp(mu + sigma^2/2)^2 = exp(sigma^2) - 1 We can rearrange this to sigma = sqrt(log(coeffOfVar^2 + 1)) We also know that mean = exp(mu + sigma^2/2) This rearranges to mu = log(mean) - sigma^2/2 Here's my R implementation rlnorm0 <- function(mean, coeffOfVar, n = 1e6) { sigma <- sqrt(log(coeffOfVar^2 + 1)) mu <- log(mean) - sigma^2 / 2 rlnorm(n, mu, sigma) } It works okay for small coefficients of variation r1 <- rlnorm0(2, 0.5) mean(r1) # 2.000095 sd(r1) / mean(r1) # 0.4998437 But not for larger values r2 <- rlnorm0(2, 50) mean(r2) # 2.048509 sd(r2) / mean(r2) # 68.55871 To check that it wasn't an R-specific issue, I reimplemented it in MATLAB. (Uses stats toolbox.) function y = lognrnd0(mean, coeffOfVar, sizeOut) if nargin < 3 || isempty(sizeOut) sizeOut = [1e6 1]; end sigma = sqrt(log(coeffOfVar.^2 + 1)); mu = log(mean) - sigma.^2 ./ 2; y = lognrnd(mu, sigma, sizeOut); end r1 = lognrnd0(2, 0.5); mean(r1) % 2.0013 std(r1) ./ mean(r1) % 0.5008 r2 = lognrnd0(2, 50); mean(r2) % 1.9611 std(r2) ./ mean(r2) % 22.61 Same problem. The question is, why is this happening? Is it just that the standard deviation is not robust when the variation is that wide? Or have a screwed up somewhere?

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• What's wrong with this code to un-camel-case a string?

  - by omair iqbal

  Here is my attempt to solve the About.com Delphi challenge to un-camel-case a string. unit challenge1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls; type check = 65..90; TForm1 = class(TForm) Edit1: TEdit; Button1: TButton; procedure Button1Click(Sender: TObject); private { Private declarations } public { Public declarations } end; var Form1: TForm1; var s1,s2 :string; int : integer; implementation {$R *.dfm} procedure TForm1.Button1Click(Sender: TObject); var i: Integer; checks : set of check; begin s1 := edit1.Text; for i := 1 to 20 do begin int :=ord(s1[i]) ; if int in checks then insert(' ',s1,i-1); end; showmessage(s1); end; end. check is a set that contains capital letters so basically whenever a capital letter is encountered the insert function adds space before its encountered (inside the s1 string), but my code does nothing. ShowMessage just shows text as it was entered in Edit1. What have I done wrong?

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• C# reflection instantiation

  - by NickLarsen

  I am currently trying to create a generic instance factory for which takes an interface as the generic parameter (enforced in the constructor) and then lets you get instantiated objects which implement that interface from all types in all loaded assemblies. The current implementation is as follows:     public class InstantiationFactory     {         protected Type Type { get; set; }         public InstantiationFactory()         {             this.Type = typeof(T);             if (!this.Type.IsInterface)             {                 // is there a more descriptive exception to throw?                 throw new ArgumentException(/* Crafty message */);             }         }         public IEnumerable GetLoadedTypes()         {             // this line of code found in other stack overflow questions             var types = AppDomain.CurrentDomain.GetAssemblies()                 .SelectMany(a = a.GetTypes())                 .Where(/* lambda to identify instantiable types which implement this interface */);             return types;         }         public IEnumerable GetImplementations(IEnumerable types)         {             var implementations = types.Where(/* lambda to identify instantiable types which implement this interface */                 .Select(x = CreateInstance(x));             return implementations;         }         public IEnumerable GetLoadedImplementations()         {             var loadedTypes = GetLoadedTypes();             var implementations = GetImplementations(loadedTypes);             return implementations;         }         private T CreateInstance(Type type)         {             T instance = default(T);             var constructor = type.GetConstructor(Type.EmptyTypes);             if (/* valid to instantiate test */)             {                 object constructed = constructor.Invoke(null);                 instance = (T)constructed;             }             return instance;         }     } It seems useful to me to have my CreateInstance(Type) function implemented as an extension method so I can reuse it later and simplify the code of my factory, but I can't figure out how to return a strongly typed value from that extension method. I realize I could just return an object:     public static class TypeExtensions     {         public object CreateInstance(this Type type)         {             var constructor = type.GetConstructor(Type.EmptyTypes);             return /* valid to instantiate test */ ? constructor.Invoke(null) : null;         }     } Is it possible to have an extension method create a signature per instance of the type it extends? My perfect code would be this, which avoids having to cast the result of the call to CreateInstance():     Type type = typeof(MyParameterlessConstructorImplementingType);     MyParameterlessConstructorImplementingType usable = type.CreateInstance();

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• Null Safe dereferencing in Java like ?. in Groovy using Maybe monad

  - by Sathish

  I'm working on a codebase ported from Objective C to Java. There are several usages of method chaining without nullchecks dog.collar().tag().name() I was looking for something similar to safe-dereferencing operator ?. in Groovy instead of having nullchecks dog.collar?.tag?.name This led to Maybe monad to have the notion of Nothing instead of Null. But all the implementations of Nothing i came across throw exception when value is accessed which still doesn't solve the chaining problem. I made Nothing return a mock, which behaves like NullObject pattern. But it solves the chaining problem. Is there anything wrong with this implementation of Nothing? [http://github.com/sathish316/jsafederef/blob/master/src/s2k/util/safederef/Nothing.java] As far as i can see 1. It feels odd to use mocking library in code 2. It doesn't stop at the first null. 3. How do i distinguish between null result because of null reference or name actually being null? How is it distinguished in Groovy code?

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• Objective-C Getter Memory Management

  - by Marian André

  I'm fairly new to Objective-C and am not sure how to correctly deal with memory management in the following scenario: I have a Core Data Entity with a to-many relationship for the key "children". In order to access the children as an array, sorted by the column "position", I wrote the model class this way: @interface AbstractItem : NSManagedObject { NSArray * arrangedChildren; } @property (nonatomic, retain) NSSet * children; @property (nonatomic, retain) NSNumber * position; @property (nonatomic, retain) NSArray * arrangedChildren; @end @implementation AbstractItem @dynamic children; @dynamic position; @synthesize arrangedChildren; - (NSArray*)arrangedChildren { NSArray* unarrangedChildren = [[self.children allObjects] retain]; NSSortDescriptor* sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"position" ascending:YES]; [arrangedChildren release]; arrangedChildren = [unarrangedChildren sortedArrayUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]]; [sortDescriptor release]; [unarrangedChildren release]; return [arrangedChildren retain]; } @end I'm not sure whether or not to retain unarrangedChildren and the returned arrangedChildren (first and last line of the arrangedChildren getter). Does the NSSet allObjects method already return a retained array? It's probably too late and I have a coffee overdose. I'd be really thankful if someone could point me in the right direction. I guess I'm missing vital parts of memory management knowledge and I will definitely look into it thoroughly.

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• Should a new language compiler target the JVM?

  - by Pindatjuh

  I'm developing a new language. My initial target was to compile to native x86 for the Windows platform, but now I am in doubt. I've seen some new languages target the JVM (most notable Scala and Clojure). Ofcourse it's not possible to port every language easily to the JVM; to do so, it may lead to small changes to the language and it's design. So that's the reason behind this doubt, and thus this question: Is targetting the JVM a good idea, when creating a compiler for a new language? Or should I stick with x86? I have experience in generating JVM bytecode. Are there any workarounds to JVM's GC? The language has deterministic implicit memory management. How to produce JIT-compatible bytecode, such that it will get the highest speedup? Is it similar to compiling for IA-32, such as the 4-1-1 muops pattern on Pentium? I can imagine some advantages (please correct me if I'm wrong): JVM bytecode is easier than x86. Like x86 communicates with Windows, JVM communicates with the Java Foundation Classes. To provide I/O, Threading, GUI, etc. Implementing "lightweight"-threads.I've seen a very clever implementation of this at http://www.malhar.net/sriram/kilim/. Most advantages of the Java Runtime (portability, etc.) The disadvantages, as I imagined, are: Less freedom? On x86 it'll be more easy to create low-level constructs, while JVM has a higher level (more abstract) processor. Most disadvantages of the Java Runtime (no native dynamic typing, etc.)

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• How to get the title and subtitle for a pin when we are implementing the MKAnnotation?

  - by wolverine

  I have implemented the MKAnnotation as below. I will put a lot of pins and the information for each of those pins are stored in an array. Each member of this array is an object whose properties will give the values for the title and subtitle of the pin. Each object corresponds to a pin. But how can I display these values for the pin when I click a pin?? @interface UserAnnotation : NSObject <MKAnnotation> { CLLocationCoordinate2D coordinate; NSString *title; NSString *subtitle; NSString *city; NSString *province; } @property (nonatomic, assign) CLLocationCoordinate2D coordinate; @property (nonatomic, retain) NSString *title; @property (nonatomic, retain) NSString *subtitle; @property (nonatomic, retain) NSString *city; @property (nonatomic, retain) NSString *province; -(id)initWithCoordinate:(CLLocationCoordinate2D)c; And .m is @implementation UserAnnotation @synthesize coordinate, title, subtitle, city, province; - (NSString *)title { return title; } - (NSString *)subtitle { return subtitle; } - (NSString *)city { return city; } - (NSString *)province { return province; } -(id)initWithCoordinate:(CLLocationCoordinate2D)c { coordinate=c; NSLog(@"%f,%f",c.latitude,c.longitude); return self; } @end

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• Looking for a specific featured content slider script - PHP (and jQuery, I think)

  - by Sootah

  I was looking around a few days ago for a new script to replace the featured content area on my website's current implementation. Randomly, I can across a gorgeous one that I have not been able to find again because, like an idiot, I didn't bookmark the page. It's difficult to explain what the slider looked like, so I'll try to make a crude ASCII image of it: When you would hover your mouse over one of the "title" areas that were visible, the rest of the tags would slide to the right and show the one you were hovering on. You could also hover the mouse over a tab on the right and the tabs would collapse left for the same effect. I don't know if this particular effect has a specific name to it, but for the life of me I cannot find this script again, or anything even like it. It was gorgeous. I've resorted to combing through my browser history, but there is sooooo much of it, and I cannot remember what day I saw it. So, if any of you know either what the name of this effect is, or even BETTER, what script I'm talking about, I would REAAAAALLLLYYY appreciate a link! Thanks as always! -Sootah

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• How to assign a table view controller to a table view on iPhone?

  - by Tattat

  I have a CharTableController, View and TableView on my IB. The CharTableController is using "CharTableController" in class identity. And this is how I implemented in the .h, and I want use the "CharTableController" to control the table only: @interface CharTableController : UITableViewController <UITableViewDelegate, UITableViewDataSource>{ // IBOutlet UILabel *debugLabel; NSArray *listData; } //@property (nonatomic, retain) IBOutlet UILabel *debugLabel; @property (nonatomic, retain) NSArray *listData; @end It is the .m: #import "CharTableController.h" @implementation CharTableController @synthesize listData; - (void)viewDidLoad { //NSLog(@"bulll"); // [debugLabel setText:@"success"]; NSArray *array = [[NSArray alloc] initWithObjects:@"A", @"B", @"C", @"D", @"E", nil]; self.listData = array; [array release]; [super viewDidLoad]; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return [self.listData count]; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *SimpleTableIdentifier = @"SimpleTableIdentifier"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier: SimpleTableIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:SimpleTableIdentifier] autorelease]; NSUInteger row = [indexPath row]; cell.textLabel.text = [listData objectAtIndex:row]; } return cell; } @end In the IB, I already assign the CharTableController's view to Table View in IB. And Table View is under the View, in IB. After I run the program, I can see the table view, but I can't see any char in the table view, why? What's wrong with my code? thz.

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• Orphan IBM JVM process

  - by Nicholas Key

  Hi people, I have this issue about orphan IBM JVM process being created in the process tree: For example: C:\Program Files\IBM\WebSphere\AppServer\bin>wsadmin -lang jython -f "C:\Hello.py" Hello.py has the simple implementation: import time i = 0 while (1): i = i + 1 print "Hello World " + str(i) time.sleep(3.0) My machine has such JVM information: C:\Program Files\WebSphere\java\bin>java -verbose:sizes -version -Xmca32K RAM class segment increment -Xmco128K ROM class segment increment -Xmns0K initial new space size -Xmnx0K maximum new space size -Xms4M initial memory size -Xmos4M initial old space size -Xmox1624995K maximum old space size -Xmx1624995K memory maximum -Xmr16K remembered set size -Xlp4K large page size available large page sizes: 4K 4M -Xmso256K operating system thread stack size -Xiss2K java thread stack initial size -Xssi16K java thread stack increment -Xss256K java thread stack maximum size java version "1.6.0" Java(TM) SE Runtime Environment (build pwi3260sr6ifix-20091015_01(SR6+152211+155930+156106)) IBM J9 VM (build 2.4, JRE 1.6.0 IBM J9 2.4 Windows Server 2003 x86-32 jvmwi3260sr6-20091001_43491 (JIT enabled, AOT enabled) J9VM - 20091001_043491 JIT - r9_20090902_1330ifx1 GC - 20090817_AA) JCL - 20091006_01 While the program is running, I tried to kill it and subsequently I found an orphan IBM JVM process in the process tree. Is there a way to fix this issue? Why is there an orphan process in the first place? Is there something wrong with my code? I really don't believe that my simplistic code is wrongly implemented. Any suggestions?

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• PHPExcel reading columns

  - by user1270150

  I am new to using the PHPExcel and am struggling to implement a basic reader that can be used to read only specified columns, with all rows from a spreadsheet into an array, which I would like to present in a webpage. After reading the supplied documentation and examples, I am struggling to wrap my head round the implementation of a number of examples, so any help would be much appreciated. I am using the following code to get the contents of the default worksheet into an array: for ($row = 2; $row <= $highestRow; $row++) { $dataRow = $objWorksheet->rangeToArray('A'.$row.':'.$highestColumn.$row,null, true, true, true); if ((isset($dataRow[$row]['A'])) && ($dataRow[$row]['A'] > '')) { ++$r; foreach($headingsArray as $columnKey => $columnHeading) { $columnHeading = rtrim($columnHeading); $columnHeading = preg_replace('/\s+/', ' ',$columnHeading); $columnHeading = preg_replace('/\ /', '_',$columnHeading); $columnHeading = strtolower($columnHeading); $namedDataArray[$r][$columnHeading] = $dataRow[$row][$columnKey]; } } } Above code reads through all the columns and rows and builds and array, but I would like to be able to add a configuration array that will declare columns that should be read...sure this is possible, so any help would be much appreciated. Thanks

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• IPhone SDK help with minigame

  - by Harry

  right basically what ive got is an app which is a ball and bat and its how many bounces you can achieve, it works alright but there is one problem, when the ball hits the side of the bat it throws it off course and its like the frame of the ball is bouncing in the frame of the bat, Here is my code in my mainview.m #import "MainView.h" #define kGameStateRunning 1 @implementation MainView @synthesize paddle, ball; - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [[event allTouches] anyObject]; CGPoint location = [touch locationInView:touch.view]; CGPoint xLocation = CGPointMake(location.x,paddle.center.y); paddle.center = xLocation; } -(IBAction) play { pos = CGPointMake(14.0,7.0); [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(onTimer) userInfo:nil repeats:YES]; } -(void) onTimer { ball.center = CGPointMake(ball.center.x+pos.x,ball.center.y+pos.y); if(ball.center.x > 320 || ball.center.x < 0) pos.x = -pos.x; if(ball.center.y > 460 || ball.center.y < 0) pos.y = -pos.y; [self checkCollision]; } -(void) checkCollision { if(CGRectIntersectsRect(ball.frame,paddle.frame)) { pos.y = -pos.y; } } @end can anyone work out the problem here? Thanks Harry

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• Apache module, is it possible to have asynchronous processing

  - by prashant2361

  Hi, I have a requirement where I need to send continous updates to my clients. Client is browser in this case. We have some data which updates every sec, so once client connects to our server, we maintain a persistent connection and keep pushing data to the client. I am looking for suggestions of this implementation at the server end. Basically what I need is this: 1. client connects to server. I maintain the socket and metadata about the socket. metadata contains what updates need to be send to this client 2. server process now waits for new client connections 3. One other process will have the list of all the sockets opened and will go through each of them and send the updates if required. Can we do something like this in apache module: 1. apache process gets the new connection. It maintains the state for the connection. It keeps the state in some global memory and returns back to root process to signify that it is done so that it can accept the new connection 2. the apache process though has returned the status to root process but it is also executing parallely where it going through its global store and sending updates to the client, if any. So can a apache process do these things: 1. Have more than one connection associated with it 2. Asynchronously waiting for new connection and at the same time processing the previous connections? Regards Prashant

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• hadoop implementing a generic list writable

  - by Guruprasad Venkatesh

  I am working on building a map reduce pipeline of jobs(with one MR job's output feeding to another as input). The values being passed around are fairly complex, in that there are lists of different types and hash maps with values as lists. Hadoop api does not seem to have a ListWritable. Am trying to write a generic one, but it seems i can't instantiate a generic type in my readFields implementation, unless i pass in the class type itself: public class ListWritable<T extends Writable> implements Writable { private List<T> list; private Class<T> clazz; public ListWritable(Class<T> clazz) { this.clazz = clazz; list = new ArrayList<T>(); } @Override public void write(DataOutput out) throws IOException { out.writeInt(list.size()); for (T element : list) { element.write(out); } } @Override public void readFields(DataInput in) throws IOException{ int count = in.readInt(); this.list = new ArrayList<T>(); for (int i = 0; i < count; i++) { try { T obj = clazz.newInstance(); obj.readFields(in); list.add(obj); } catch (InstantiationException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } } } } But hadoop requires all writables to have a no argument constructor to read the values back. Has anybody tried to do the same and solved this problem? TIA.

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• How to convert source code to a xml based representation of the ast?

  - by autobiographer

  i wanna get a xml representation of the ast of java and c code. 3 months ago, i asked this question yet but the solutions weren't comfortable for me srcml seems to be a good solution for this problem but it does not support line numbers and columns but i need that feature. about elsa: cite: "There is ongoing effort to export the Elsa AST as an XML document; we expect to be able to advertise this in the next public release." dms... didn't understand that. especially for java, there is javaml which supports line numbers. but the sourceforge page doesn't list any files. question: there's software available which supports conversion of ast into xml which supports line numbers (and columns) [especially for java and c/c++]? is there an alternative to javaml and srcml? ps: i don't wanne have parser generators. i hope to find a tool which can be used on the console typing: ./my-xml-generator Test.java [or something like that]... or a java implementation would be great too.

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• RSA_sign and RSACryptoProvider.VerifySignature

  - by Miky D

  I'm trying to get up to speed on how to get some code that uses OpenSSL for cryptography, to play nice with another program that I'm writing in C#, using the Microsoft cryptography providers available in .NET. More to the point, I'm trying to have the C# program verify an RSA message signature generated by the OpenSSL code. The code that generates the signature looks something like this: // Code in C, using the OpenSSL RSA implementation char msgToSign[] = "Hello World"; // the message to be signed char signature[RSA_size(rsa)]; // buffer that will hold signature int slen = 0; // will contain signature size // rsa is an OpenSSL RSA context, that's loaded with the public/private key pair memset(signature, 0, sizeof(signature)); RSA_sign(NID_sha1 , (unsigned char*)msgToSign , strlen(msgToSign) , signature , &slen , rsa); // now signature contains the message signature // and can be verified using the RSA_verify counterpart // .. I would like to verify the signature in C# In C#, I would do the following: import the other side's public key into an RSACryptoServiceProvider object receive the message and it's signature try to verify the signature I've got the first two parts working (I've verified that the public key is loading properly because I managed to send an RSA encrypted text from the C# code to the OpenSSL code in C and successfully have it decrypted) In order to verify the signature in C#, I've tried using the: VerifySignature method of the RSACryptoServiceProvider but that didn't work. And digging around the internet I was only able to find some vague information pointing out that .NET uses a different method for generating the signature than OpenSSL does. So, does anybody know how to accomplish this?

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• My cocoa app won't capture key events

  - by Oscar

  Hi, i usually develop for iPhone. But now trying to make a pong game in Cocoa desktop application. Working out pretty well, but i can't find a way to capture key events. Here's my code: #import "PongAppDelegate.h" #define GameStateRunning 1 #define GameStatePause 2 #define BallSpeedX 10 #define BallSpeedY 15 @implementation PongAppDelegate @synthesize window, leftPaddle, rightPaddle, ball; - (void)applicationDidFinishLaunching:(NSNotification *)aNotification { gameState = GameStateRunning; ballVelocity = CGPointMake(BallSpeedX, BallSpeedY); [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(gameLoop) userInfo:nil repeats:YES]; } - (void)gameLoop { if(gameState == GameStateRunning) { [ball setFrameOrigin:CGPointMake(ball.frame.origin.x + ballVelocity.x, ball.frame.origin.y + ballVelocity.y)]; if(ball.frame.origin.x + 15 > window.frame.size.width || ball.frame.origin.x < 0) { ballVelocity.x =- ballVelocity.x; } if(ball.frame.origin.y + 35 > window.frame.size.height || ball.frame.origin.y < 0) { ballVelocity.y =- ballVelocity.y; } } } - (void)keyDown:(NSEvent *)theEvent { NSLog(@"habba"); // Arrow keys are associated with the numeric keypad if ([theEvent modifierFlags] & NSNumericPadKeyMask) { [window interpretKeyEvents:[NSArray arrayWithObject:theEvent]]; } else { [window keyDown:theEvent]; } } - (void)dealloc { [ball release]; [rightPaddle release]; [leftPaddle release]; [super dealloc]; } @end

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• Collision detections and how efficient they are

  - by Shadow

  How exactly do you implement collision detection? What are the costs involved? Do different platforms(c/c++, java, cocoa/iphone, flash, directX) have different optimizations for calculating collisions. And lastly are there libraries available to do this for me, or some that I can just interpret for my platform of choice? As I understand it you would need to loop through the collision map and find the area in question and then compair the input thing(e.g. a sprite) to the type of pixel that is in the questioned area. I understand the very basic idea, but I don't understand the underlying implementation or even a higher level one for that matter. It would seem that this type of detection, or any for that matter, is very costly. Tile map? Bit array? How are these created from an image(I would guess looping and doing stuff)? The reason I ask this question is to get a better understanding of the efficiency behind the scenes and to understand exactly what is going on. Links, references, or examples would be very helpful. I know this question is a bit longwinded so any help or references would be very welcome. Thanks SO!

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• Algorithm for scoring user activity

  - by ManBugra

  I have an application where users can: Write reviews about products Add comments to products Up / Down vote reviews Up / Down vote comments Every Up/Down vote is recorded in a db table. What i want to do now is to create a ranking of the most active users in the last 4 weeks. Of course good reviews should be weighted more than good comments. But also e.g. 10 good comments should be weighted more than just one good review. Example: // reviews created in recent 4 weeks //format: [ upVoteCount, downVoteCount ] var reviews = [ [120,23], [32,12], [12,0], [23,45] ]; // comments created in recent 4 weeks // format: [ upVoteCount, downVoteCount ] var comments = [ [1,2], [322,1], [0,0], [0,45] ]; // create weight vector // format: [ reviewWeight, commentsWeight ] var weight = [0.60, 0.40]; // signature: activties..., activityWeight var userActivityScore = score(reviews, comments, weight); ... update user table ... List<Users> users = "from users u order by u.userActivityScore desc"; How would a fair scoring function look like? How could an implementation of the score() function look like? How to add a weight g to the function so that reviews are weighted heavier? How would such a function look like if, for example, votes for pictures would be added?

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• How to allow one thread to mutate an array property while another thread iterates on a copy of the a

  - by Steve918

  I would like to implement an observer pattern in Objective-C where the observer implements an interface similar to SKPaymentTransactionObserver and the observable class just extends my base observable. My observable class looks something like what is below. Notice I'm making copies of the observers before enumeration to avoid throwing an exception . I've tried adding an NSLock around add observers and notify observers, but I run into a deadlock. What would be the proper way to handle concurrency when observers are being added as notifications are being sent? @implementation Observable -(void)notifyObservers:(SEL)selector { @synchronized(self) { NSSet* observer_copy = [observers copy]; for (id observer in observer_copy) { if([observer respondsToSelector: selector]) { [observer performSelector: selector]; } } [observer_copy release]; } } -(void)notifyObservers:(SEL)selector withObject:(id)arg1 withObject:(id)arg2 { @synchronized(self) { NSSet* observer_copy = [observers copy]; for (id observer in observer_copy) { if([observer respondsToSelector: selector]) { [observer performSelector: selector withObject: arg1 withObject: arg2]; } } [observer_copy release]; } } -(void)addObserver:(id)observer { @synchronized(self) { [observers addObject: observer]; } } -(void)removeObserver:(id)observer { @synchronized(self) { [observers removeObject: observer]; } }

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• Mono WCF NetTcp service takes only one client at a time

  - by vene

  While trying to build a client-server WCF application in Mono we ran into some issues. Reducing it to just a bare example we found that the service only accepts one client at a time. If another client attempts to connect, it hangs until the first one disconnects. Simply changing to BasicHttpBinding fixes it but we need NetTcpBinding for duplex communication. Also the problem does not appear if compiled under MS .NET. EDIT: I doubt (and hope not) that Mono doesn't support what I'm trying to do. Mono code usually throws NotImplementedExceptions in such cases as far as I noticed. I am using Mono v2.6.4 This is how the service is opened in our basic scenario: public static void Main (string[] args) { var binding = new NetTcpBinding (); binding.Security.Mode = SecurityMode.None; var address = new Uri ("net.tcp://localhost:8080"); var host = new ServiceHost (typeof(Hello)); host.AddServiceEndpoint (typeof(IHello), binding, address); ServiceThrottlingBehavior behavior = new ServiceThrottlingBehavior () { MaxConcurrentCalls = 100, MaxConcurrentSessions = 100, MaxConcurrentInstances = 100 }; host.Description.Behaviors.Add (behavior); host.Open (); Console.ReadLine (); host.Close (); } The client channel is obtained like this: var binding = new NetTcpBinding (); binding.Security.Mode = SecurityMode.None; var address = new EndpointAddress ("net.tcp://localhost:8080/"); var client = new ChannelFactory<IHello> (binding, address).CreateChannel (); As far as I know this is a Simplex connection, isn't it? The contract is simply: [ServiceContract] public interface IHello { [OperationContract] string Greet (string name); } Service implementation has no ServiceModel tags or attributes. I'll update with details as required.

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• How can i get rid of 0xFEEFEE in VC

  - by egebilmuh

  Hi guys I m programming C for an assingment in VC++ 2008. I simulate adjList for graph implementation. i can readly add edge between two vertex and print the graph. and i want to remove edge between two vertex and print the graph again. whatever i do,i cant print the graph after deleting the edge. i get 0xfeefee :( what is this? and how can i resolve this program. my delete function and print the graph function are illustrated below. void deleteEdge(Graph G, Vertex V, Vertex W) { Edge list,prev,temp; list=V->list; prev=NULL; // while(list!=NULL && list->to->value!=W->value){ prev=list; list=list->next; } // have found the element. if(list!=NULL){ temp=list; // if first element of list is deleted. if(prev==NULL) list=list->next; else prev->next=list->next; // reallocate. free(temp); } } void GRAPHprint(Graph G) { Vertex tmp; Edge list; for(tmp = G->head;tmp!=NULL;tmp=tmp->next) { fprintf(stdout,"V:%d\t",tmp->value); list=tmp->list; while(list!=NULL) { fprintf(stdout,"%d\t",list->to->value); list=list->next; } fprintf(stdout, "\n"); } system("pause"); }

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• Go for Zend framework or Django for a modular web application?

  - by dr. squid

  I am using both Zend framework and Django, and they both have they strengths and weakness, but they are both good framworks in their own way. I do want to create a highly modular web application, like this example: modules: Admin cms articles sections ... ... ... I also want all modules to be self contained with all confid and template files. I have been looking into a way to solve this is zend the last days, but adding one omer level to the module setup doesn't feel right. I am sure this could be done, but should I? I have also included Doctrine to my zend application that could give me even more problems in my module setup! When we are talking about Django this is easy to implement (Easy as in concept, not in implementation time or whatever) and a great way to create web apps. But one of the downsides of Django is the web hosing part. There are some web hosts offering Django support, but not that many.. So then I guess the question is what have the most value; rapid modular development versus hosting options! Well, comments are welcome! Thanks

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