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• Matrix multiplication using pairs

  - by sc_ray

  Hi, I am looking into alternate ways to do a Matrix Multiplication. Instead of storing my matrix as a two-dimensional array, I am using a vector such as vector<pair<pair<int,int >,int > > to store my matrix. The pair within my pair (pair) stores my indices (i,j) and the other int stores the value for the given (i,j) pair. I thought I might have some luck implementing my sparse array this way. The problem is when I try to multiply this matrix with itself. If this was a 2-d array implementation, I would have multiplied the matrix as follows: for(i=0; i<row1; i++) { for(j=0; j<col1; j++) { C[i][j] = 0; for(k=0; k<col2; k++) C[i][j] += A[i][j] * A[j][k]; } } Can somebody point out a way to achieve the same result using my vector of 'pair of pairs'? Thanks

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• Invoking different methods on threads

  - by Kraken

  I have a main process main. It creates 10 threads (say) and then what i want to do is the following: while(required){ Thread t= new Thread(new ClassImplementingRunnable()); t.start(); counter++; } Now i have the list of these threads, and for each thread i want to do a set of process, same for all, hence i put that implementation in the run method of ClassImplementingRunnable. Now after the threads have done their execution, i wan to wait for all of them to stop, and then evoke them again, but this time i want to do them serially not in parallel. for this I join each thread, to wait for them to finish execution but after that i am not sure how to evoke them again and run that piece of code serially. Can i do something like for(each thread){ t.reevoke(); //how can i do that. t.doThis(); // Also where does `dothis()` go, given that my ClassImplementingRunnable is an inner class. } Also, i want to use the same thread, i.e. i want the to continue from where they left off, but in a serial manner. I am not sure how to go about the last piece of pseudo code. Kindly help. Working with with java.

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• Complicated .NET factory design

  - by Tom W

  Hello SO; I'm planning to ask a fairly elaborate question that is also something of a musing here, so bear with me... I'm trying to design a factory implementation for a simulation application. The simulation will consist of different sorts of entities i.e. it is not a homogenous simulation in any respect. As a result, there will be numerous very different concrete implementations and only the very general properties will be abstracted at the top level. What I'd like to be able to do is create new simulation entities by calling a method on the model with a series of named arguments representing the parameters of the entity, and have the model infer what type of object is being described by the inbound parameters (from the names of the parameters and potentially the sequence they occur in) and call a factory method on the appropriate derived class. For example, if I pass the model a pair of parameters (Param1=5000, Param2="Bacon") I would like it to infer that the names Param1 and Param2 'belong' to the class "Blob1" and call a shared function "getBlob1" with named parameters Param1:=5000, Param2:="Bacon" whereas if I pass the model (Param1=5000, Param3=50) it would call a similar factory method for Blob2; because Param1 and Param3 in that order 'belong' to Blob2. I foresee several issues to resolve: Whether or not I can reflect on the available types with string parameter names and how to do this if it's possible Whether or not there's a neat way of doing the appropriate constructor inference from the combinatoric properties of the argument list or whether I'm going to have to bodge something to do it 'by hand'. If possible I'd like the model class to be able to accept parameters as parameters rather than as some collection of keys and values, which would require the model to expose a large number of parametrised methods at runtime without me having to code them explicitly - presumably one for every factory method available in the relevant namespace. What I'm really asking is how you'd go about implementing such a system, rather than whether or not it's fundamentally possible. I don't have the foresight or experience with .NET reflection to be able to figure out a way by myself. Hopefully this will prove an informative discussion.

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• How am i overriding this C++ inherited member function without the virtual keyword being used?

  - by Gary Willoughby

  I have a small program to demonstrate simple inheritance. I am defining a Dog class which is derived from Mammal. Both classes share a simple member function called ToString(). How is Dog overriding the implementation in the Mammal class, when i'm not using the virtual keyword? (Do i even need to use the virtual keyword to override member functions?) mammal.h #ifndef MAMMAL_H_INCLUDED #define MAMMAL_H_INCLUDED #include <string> class Mammal { public: std::string ToString(); }; #endif // MAMMAL_H_INCLUDED mammal.cpp #include <string> #include "mammal.h" std::string Mammal::ToString() { return "I am a Mammal!"; } dog.h #ifndef DOG_H_INCLUDED #define DOG_H_INCLUDED #include <string> #include "mammal.h" class Dog : public Mammal { public: std::string ToString(); }; #endif // DOG_H_INCLUDED dog.cpp #include <string> #include "dog.h" std::string Dog::ToString() { return "I am a Dog!"; } main.cpp #include <iostream> #include "dog.h" using namespace std; int main() { Dog d; std::cout << d.ToString() << std::endl; return 0; } output I am a Dog! I'm using MingW on Windows via Code::Blocks.

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• Service behavior not being applied correctly

  - by Rubans

  I have a custom behavior for a service where I want to specify a receive timeout value, I have created a behavior and on the build service header. I use the declarative attribute to apply the behavior or as I thought. But the behavior seems to make no difference, i.e. the set timeout value is not being applied as expected. However when I have noticed the behavior is only being applied when the host is opened rather than when created. The same behavior when applied explicitly through does work. Any ideas? Behavior: [AttributeUsage(AttributeTargets.Class)] public class BuildServiceBindingBehavior : Attribute, IServiceBehavior { public BuildServiceBindingBehavior( string p_receiveTime ) { ReceiveTimeout = TimeSpan.Parse( p_receiveTime ); } #region IServiceBehavior Members public void AddBindingParameters( ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, System.Collections.ObjectModel.Collection<ServiceEndpoint> endpoints, System.ServiceModel.Channels.BindingParameterCollection bindingParameters ) { } public void ApplyDispatchBehavior( ServiceDescription serviceDescription, ServiceHostBase serviceHostBase ) { // add this behavior to each endpoint foreach ( var endPoint in serviceDescription.Endpoints ) { endPoint.Binding.ReceiveTimeout = ReceiveTimeout; } } public void Validate( ServiceDescription serviceDescription, ServiceHostBase serviceHostBase ) { } #endregion internal TimeSpan ReceiveTimeout { get; set; } } Service code: [ServiceBehavior(Name = "DotNetBuildsService", InstanceContextMode = InstanceContextMode.PerSession, ConcurrencyMode = ConcurrencyMode.Single )] // Set receieve time out [BuildServiceBindingBehavior( "0:0:1" )] public class BuildService : IBuildTasksService { //implementation code }

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• Silverlight: Button template with texttrimming cut off

  - by dex3703

  I'm replacing the default Button template's ContentPresenter with a TextBlock, so the text can be trimmed when it's too long. Works fine in WPF. In Silverlight the text gets pushed to one edge and cut off on the left, even when there's space on the right: Template is nothing special, just replaced the ContentPresenter with the TextBlock: <Border x:Name="bdrBackground" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" /> <Rectangle x:Name="rectMouseOverVisualElement" Opacity="0"> <Rectangle.Fill> <SolidColorBrush x:Name="rectMouseOverColor" Color="{StaticResource MouseOverItemBgColor}"/> </Rectangle.Fill> </Rectangle> <Rectangle x:Name="rectPressedVisualElement" Opacity="0" Style="{TemplateBinding Tag}"/> <TextBlock x:Name="textblock" Text="{TemplateBinding Content}" TextTrimming="WordEllipsis" TextWrapping="NoWrap" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/> <Rectangle x:Name="rectDisabledVisualElement" Opacity="0" Style="{StaticResource RectangleDisabledStyle}"/> <Rectangle x:Name="rectFocusVisualElement" Opacity="0" Style="{StaticResource RectangleFocusStyle}"/> </Grid> </ControlTemplate> How do I fix this? More info: With the latest comment about HorizontalAlignment, it's clear that SL's implementation of TextTrimming differs from WPF's. In SL, TextTrimming only really works if the text is aligned left. SL isn't smart enough to align the text the way WPF does. For instance: WPF button: SL button with the textblock horizontalalignment = left: SL button with textblock horizontalalignment = center:

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• UIWebView autosize issue only on iOS 4.3

  - by troop231

  I am trying to figure out how to fix this bug that only occurs on iOS 4.3. When the application launches, it displays a PDF that is scaled to fit in the UIWebView. It behaves perfectly until you pinch to zoom on the document, and then rotate it, leaving behind a black area. If you don't pinch to zoom, it doesn't leave the black area. I don't understand why this is a iOS 4.3 only issue. Screenshot of the issue: I've been trying to solve this problem awhile now, and would greatly appreciate your help. Thank you. Screenshots of the .xib settings: The code I'm using is: .h: #import <UIKit/UIKit.h> @interface ViewController : UIViewController { UIWebView *webView; } @property (nonatomic) IBOutlet UIWebView *webView; @end .m: #import "ViewController.h" @interface ViewController () @end @implementation ViewController @synthesize webView; - (BOOL)shouldAutorotateToInterfaceOrientation: (UIInterfaceOrientation)interfaceOrientation { if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { return YES; } else { return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown); } } - (void)viewDidLoad { [super viewDidLoad]; NSString *urlAddress = [[NSBundle mainBundle] pathForResource:@"test" ofType:@"pdf"]; NSURL *url = [NSURL fileURLWithPath:urlAddress]; NSURLRequest *requestObj = [NSURLRequest requestWithURL:url]; [webView loadRequest:requestObj]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; } @end

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• initialise a var in scala

  - by user unknown

  I have a class where I like to initialize my var by reading a configfile, which produces intermediate objects/vals, which I would like to group and hide in a method. Here is the bare minimum of the problem - I call the ctor with a param i, in reality a File to parse, and the init-method generates the String s, in reality more complicated than here, with a lot of intermediate objects being created: class Foo (val i: Int) { var s : String; def init () { s = "" + i } init () } This will produce the error: class Foo needs to be abstract, since variable s is not defined. In this example it is easy to solve by setting the String to "": var s = "";, but in reality the object is more complex than String, without an apropriate Null-implementation. I know, I can use an Option, which works for more complicated things than String too: var s : Option [String] = None def init () { s = Some ("" + i) } or I can dispense with my methodcall. Using an Option will force me to write Some over and over again, without much benefit, since there is no need for a None else than to initialize it that way I thought I could. Is there another way to achieve my goal?

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• novice needing help on shuffeling an array

  - by steffen Myklebust

  Please help a TOTAL beginner.! I found this post: http://stackoverflow.com/questions/56648/whats-the-best-way-to-shuffle-an-nsmutablearray And as i try to deploy this in my own code, I cant get it working... :-( Can anyone help me to resolve this code? To me it looks like the shuffle function is not called..? here is my code: // // shuffle2ViewController.h // shuffle2 #import @interface shuffle2ViewController : UIViewController { NSMutableArray *puzzles; int *randomSort; } - (void)shuffle; @end //============================= // shuffle2ViewController.m ´#import "shuffle2ViewController.h" @implementation shuffle2ViewController (void)viewDidLoad { [super viewDidLoad]; NSMutableArray *puzzles = [NSMutableArray arrayWithObjects:@"1",@"2",@"3", @"4",@"5",@"6",@"7",@"8",@"9", @"10",@"11",@"12", nil]; // Call the shuffle function [self shuffle]; // print to log int i; NSLog(@"NEW OLD"); NSLog(@"================="); for (i = 0; i < 12; ++i) NSLog(@" %2i %@", i + 1, [puzzles objectAtIndex:i]); } int randomSort(id obj1, id obj2, void *context ) { // returns random number -1 0 1 return (random()%3 - 1); } (void)shuffle { // call custom sort function [puzzles sortUsingFunction:randomSort context:nil]; } Giving this result: NEW OLD ================= 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10 11 11 12 12

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• Reverse engineering and redistributing code from .NET Framework

  - by ToxicAvenger

  Once or twice I have been running into the following issue: Classes I want to reuse in my applications (and possibly redistribute) exist in the .NET Framework assemblies, but are marked internal or private. So it is impossible to reuse them directly. One way is to disassemble them, pick the pieces you need, put them in a different namespace, recompile (this can be some effort, but usually works quite well). My question is: Is this legal? Is this only legal for the classes of the Framework which are available as source code anyway? Is it illegal? I think that Microsoft marks them internal or private primarily so that they don't have to support them or can change the interfaces later. But some pieces - be it SharePoint or WCF - are almost impossible to properly extend by only using public classes from the apis. And rewriting everything from scratch generates a huge amount of effort, before you even start solving the problem you intended to solve. This is in my eyes not a "dirty" approach per se. The classes Microsoft ships are obviously well tested, if I reuse them under a different namespace I have "control" over them. If Microsoft changes the original implementation, my code won't be affected (some internals in WCF changed quite a bit with v4). It is not a super-clean approach. I would much prefer Microsoft making several classes public, because there are some nice classes hidden inside the framework.

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• problems getting HTTPRiot working

  - by bwizzy

  I've got an iphone app where I'm trying to use HTTPRiot to make some API calls to a web app. Problem is I can't see that none of the HTTPRiot delegate methods are being called. I've got a log in all the delegate methods, and I'm also looking at the webserver log. I see that the URL is being hit. //API.h #import <Foundation/Foundation.h> #include <HTTPRiot/HTTPRiot.h> @interface API : HRRestModel { } +(void)runTest; @end //API.m #import "API.h" @implementation API + (void)initialize { NSLog(@"api initialize"); [self setDelegate:self]; [self setBaseURL:[NSURL URLWithString:@"http://localhost:3000/api"]]; [self setBasicAuthWithUsername:@"demo" password:@"123456"]; NSDictionary *params = [NSDictionary dictionaryWithObject:@"1234567" forKey:@"api_key"]; [self setDefaultParams:params]; }//end initialize +(void)runTest { NSLog(@"api run test"); // Would send a request to http://localhost:1234/api/people/1?api_key=1234567 [self getPath:@"/save_diet" withOptions:nil object:nil]; } +(void)restConnection:(NSURLConnection *)connection didReturnResource:(id)resource object:(id)object { NSLog(@"didReturnResource"); } +(void)restConnection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response object:(id)object { NSLog(@"didReceiveResponse"); } +(void)restConnection:(NSURLConnection *)connection didReceiveParseError:(NSError *)error responseBody:(NSString *)body object:(id)object { NSLog(@"didReceiveParseError"); } +(void)restConnection:(NSURLConnection *)connection didReceiveError:(NSError *)error response:(NSHTTPURLResponse *)response object:(id)object { NSLog(@"didReceiveError"); } +(void)restConnection:(NSURLConnection *)connection didFailWithError:(NSError *)error object:(id)object { NSLog(@"didFailWithError"); } @end //test code [API runTest]; //log output

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• Accessing red5 server outside the localhost

  - by user1039290

  I am new on red5 server so I stuck in. I am trying to record videos from webcam and save them in to my server. To do this, I installed red5 to my server. In addition, I also downloaded red5recorder and put it into my webapps folder. But there is any information about its implementation details. Whatever. So I go on with Red5 SimpleRecorder tutorial. Everything works fine when I tried in my server, but there is a problem when I try to connect to server from other computer to record a video. Actually, video recording is handled but the recorded video is not uploaded to the server. When I work in localhost it works fine, but from outside I couldn't be able to record or upload the video. I change the red5-web.properties document, and set virtual host to my server's IP but it again only works in localhost. What could be the reason? Is it about file permissions? or what could it be? Kind regards, Can

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• paypal_adaptive gem in Rails: Dynamic Receiver "Population" (Chained Payments)

  - by Jmlevick

  Note: I didn't find a better title for this O.o Hello, Humm... Look, what I want to do is to have a Rails app where a visitor can click a button/link to make a "special" chained payment using Paypal; Currently I have a Users registration form that has one field for the user to enter his/her paypal account email, and as I saw here: http://marker.to/XGg9MR it is possible to specify the primary reciever and the secondary ones by adding such info in a controller action when using the paypal_adaptive gem in a rails app. The thing is, I don't want to hard code the secondary reciever as I need to specify a different secondary reciever from time to time, (being specific my primary reciever will always be the same, but depending on what button/link the visitor clicks, the secondary one is going to change) and I want that secondary reciever email to be the paypal e-mail account from one of the registered users when the visitor clicks on their specific button/link... My question is: Is it possible to create such enviroment functionality in my app using the current implementation of the paypal_adaptive gem? Could someone point me in the right direction on how to accomplish such thing? I'm still learning rails and also I'm really new in the paypal handling universe with this framework! XD P.S. Thanks! :)

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• Datastructure choices for highspeed and memory efficient detection of duplicate of strings

  - by Jonathan Holland

  I have a interesting problem that could be solved in a number of ways: I have a function that takes in a string. If this function has never seen this string before, it needs to perform some processing. If the function has seen the string before, it needs to skip processing. After a specified amount of time, the function should accept duplicate strings. This function may be called thousands of time per second, and the string data may be very large. This is a highly abstracted explanation of the real application, just trying to get down to the core concept for the purpose of the question. The function will need to store state in order to detect duplicates. It also will need to store an associated timestamp in order to expire duplicates. It does NOT need to store the strings, a unique hash of the string would be fine, providing there is no false positives due to collisions (Use a perfect hash?), and the hash function was performant enough. The naive implementation would be simply (in C#): Dictionary<String,DateTime> though in the interest of lowering memory footprint and potentially increasing performance I'm evaluating a custom data structures to handle this instead of a basic hashtable. So, given these constraints, what would you use? EDIT, some additional information that might change proposed implementations: 99% of the strings will not be duplicates. Almost all of the duplicates will arrive back to back, or nearly sequentially. In the real world, the function will be called from multiple worker threads, so state management will need to be synchronized.

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• std::vector elements initializing

  - by Chameleon

  std::vector<int> v1(1000); std::vector<std::vector<int>> v2(1000); std::vector<std::vector<int>::const_iterator> v3(1000); How elements of these 3 vectors initialized? About int, I test it and I saw that all elements become 0. Is this standard? I believed that primitives remain undefined. I create a vector with 300000000 elements, give non-zero values, delete it and recreate it, to avoid OS memory clear for data safety. Elements of recreated vector were 0 too. What about iterator? Is there a initial value (0) for default constructor or initial value remains undefined? When I check this, iterators point to 0, but this can be OS When I create a special object to track constructors, I saw that for first object, vector run the default constructor and for all others it run the copy constructor. Is this standard? Is there a way to completely avoid initialization of elements? Or I must create my own vector? (Oh my God, I always say NOT ANOTHER VECTOR IMPLEMENTATION) I ask because I use ultra huge sparse matrices with parallel processing, so I cannot use push_back() and of course I don't want useless initialization, when later I will change the value.

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• Jquery passing an HTML element into a function

  - by christian

  I have an HTML form where I am going to copy values from a series of input fields to some spans/headings as the user populates the input fields. I am able to get this working using the following code: $('#source').keyup(function(){ if($("#source").val().length == 0){ $("#destinationTitle").text('Sample Title'); }else{ $("#destinationTitle").text($("#source").val()); } }); In the above scenario the html is something like: Sample Title Basically, as the users fills out the source box, the text of the is changed to the value of the source input. If nothing is input in, or the user deletes the values typed into the box some default text is placed in the instead. Pretty straightforward. However, since I need to make this work for many different fields, it makes sense to turn this into a generic function and then bind that function to each 's onkeyup() event. But I am having some trouble with this. My implementation: function doStuff(source,target,defaultValue) { if($(source).val().length == 0){ $(target).text(defaultValue); }else{ $(target).text($(source).val()); } } which is called as follows: $('#source').keyup(function() { doStuff(this, '"#destinationTitle"', 'SampleTitle'); }); What I can't figure out is how to pass the second parameter, the name of the destination html element into the function. I have no problem passing in the element I'm binding to via "this", but can't figure out the destination element syntax. Any help would be appreciated - many thanks!

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• .Net Hash Codes no longer persistent?

  - by RobV

  I have an API where various types have custom hash codes. These hash codes are based on getting the hash of a string representation of the object in question. Various salting techniques are used so that as far as possible Hash Codes do not collide and that Objects of different types with equivalent string representations have different Hash Codes. Obviously since the Hash Codes are based on strings there are some collisions (infinite strings vs the limited range of 32 bit integers). I use hashes based on string representations since I need the hashes to persist over sessions and particularly for use in database storage of objects. Suddenly today my code has started generating different hash codes for Objects which is breaking all kinds of things. It was working earlier today and I haven't touched any of the code involved in Hash Code generation. I'm aware that the .Net documentation allows for implementation of hash codes between .Net framework versions to change (and between 32 and 64 bit versions) but I haven't changed the framework version and there has been no framework updates recently as far as I can remember Any ideas because this seems really weird? Edit Hash Codes are generated like follows: //Compute Hash Code this._hashcode = (this._nodetype + this.ToString() + PlainLiteralHashCodeSalt).GetHashCode();

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• Strange thread behavior in Perl

  - by Zaid

  Tom Christiansen's example code (à la perlthrtut) is a recursive, threaded implementation of finding and printing all prime numbers between 3 and 1000. Below is a mildly adapted version of the script #!/usr/bin/perl # adapted from prime-pthread, courtesy of Tom Christiansen use strict; use warnings; use threads; use Thread::Queue; sub check_prime { my ($upstream,$cur_prime) = @_; my $child; my $downstream = Thread::Queue->new; while (my $num = $upstream->dequeue) { next unless ($num % $cur_prime); if ($child) { $downstream->enqueue($num); } else { $child = threads->create(\&check_prime, $downstream, $num); if ($child) { print "This is thread ",$child->tid,". Found prime: $num\n"; } else { warn "Sorry. Ran out of threads.\n"; last; } } } if ($child) { $downstream->enqueue(undef); $child->join; } } my $stream = Thread::Queue->new(3..shift,undef); check_prime($stream,2); When run on my machine (under ActiveState & Win32), the code was capable of spawning only 118 threads (last prime number found: 653) before terminating with a 'Sorry. Ran out of threads' warning. In trying to figure out why I was limited to the number of threads I could create, I replaced the use threads; line with use threads (stack_size => 1);. The resultant code happily dealt with churning out 2000+ threads. Can anyone explain this behavior?

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• WPF bound object update notification

  - by Carlo

  I have a TreeView with a few objects bound to it, let's say something like this: public class House { public List<Room> Rooms { get; set; } public List<Person> People { get; set; } public House() { this.Rooms = new List<Room>(); this.People = new List<Person>(); } public void BuildRoom(string name) { this.Rooms.Add(new Room() { Name = name }); } public void DestroyRoom(string name) { this.Rooms.Remove(new Room() { Name = name }); } public void PersonEnter(string name) { this.People.Add(new Person() { Name = name }); } public void PersonLeave(string name) { this.People.Remove(new Person() { Name = name }); } } public class Room { public string Name { get; set; } } public class Person { public string Name { get; set; } } The TreeView is watching over the House object, whenever a room is built / destroyed or a person enters / leaves, my tree view updates itself to show the new state of the house (I omitted some implementation details for simplicity). What I want is to know the exact moment when this update finishes, so I can do something right there, the thing is that I created an indicator of the selected item, and when something moves, I need to update said indicator's position, that's the reason I need it exactly when the tree view updates. Let me know if you know a solution to this. Also, the code is not perfect (DestroyRoom and PersonLeave), but you get the idea. Thanks!

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• Rapid Opening and Closing System.IO.StreamWriter in C#

  - by ccomet

  Suppose you have a file that you are programmatically logging information into with regards to a process. Kinda like your typical debug Console.WriteLine, but due to the nature of the code you're testing, you don't have a console to write onto so you have to write it somewhere like a file. My current program uses System.IO.StreamWriter for this task. My question is about the approach to using the StreamWriter. Is it better to open just one StreamWriter instance, do all of the writes, and close it when the entire process is done? Or is it a better idea to open a new StreamWriter instance to write a line into the file, then immediately close it, and do this for every time something needs to be written in? In the latter approach, this would probably be facilitated by a method that would do just that for a given message, rather than bloating the main process code with excessive amounts of lines. But having a method to aid in that implementation doesn't necessarily make it the better choice. Are there significant advantages to picking one approach or the other? Or are they functionally equivalent, leaving the choice on the shoulders of the programmer?

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• How to obtain value of auto_increment field in Access linked to MySQL?

  - by Cruachan

  I'm trying to modify and existing Access application to use MySQL as a database via ODBC with the minimal amount of recoding. The current code will often insert a new record using DAO then obtain the ID by using LastModified. This doesn't work with MySQL. Instead I'm trying to use the approach using SELECT * FROM tbl_name WHERE auto_col IS NULL Suggested for Access in the MySQL documentation. However if I set up a sample table consisting of just an id and text data field and execute this CurrentDb.Execute ("INSERT INTO tbl_scratch (DATA) VALUES ('X')") Set rst = CurrentDb.OpenRecordset("SELECT id FROM tbl_scratch WHERE id IS NULL") myid = rst!id Id is returned as null. However if I execute INSERT INTO tbl_scratch (DATA) VALUES ('X'); SELECT id FROM tbl_scratch WHERE id IS NULL; using a direct MySQL editor then id is returned correctly, so my database and approach is fine but my implementation inside Access must be incorrect. Frustratingly the MySQL documentation gives the SQL statement to retrieve the id as an example that works in Access (as it states LAST_INSERT_ID() doesn't) but gives no further details. How might I fix this?

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• Which options do I have for Java process communication?

  - by Dmitriy Matveev

  We have a place in a code of such form: void processParam(Object param) { wrapperForComplexNativeObject result = jniCallWhichMayCrash(param); processResult(result); } processParam - method which is called with many different arguments. jniCallWhichMayCrash - a native method which is intended to do some complex processing of it's parameter and to create some complex object. It can crash in some cases. wrapperForComplexNativeObject - wrapper type generated by SWIG processResult - a method written in pure Java which processes it's parameter by creation of several kinds (by the kinds I'm not meaning classes, maybe some like hierarchies) of objects: 1 - Some non-unique objects which are referencing each other (from the same hierarchy), these objects can have duplicates created from the invocations of processParam() method with different parameter values. Since it's costly to keep all the duplicates it's necessary to cache them. 2 - Some unique objects which are referencing each other (from the same hierarchy) and some of the objects of 1st kind. After processParam is executed for each of the arguments from some set the data created in processResult will be processed together. The problem is in fact that jniCallWhichMayCrash method may crash the entire JVM and this will be very bad. The reason of crash may be such that it can happen for one argument value and not for the other. We've decided that it's better to ignore crashes inside of JVM and just skip some chunks of data when such crashes occur. In order to do this we should run processParam function inside of separate process and pass the result somehow (HOW? HOW?! This is a question) to the main process and in case of any crashes we will only lose some part of data (It's ok) without lose of everything else. So for now the main problem is implementation of transport between different processes. Which options do I have? I can think about serialization and transmitting of binary data by the streams, but serialization may be not very fast due to object complexity. Maybe I have some other options of implementing this?

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• Esper generating episodes

  - by Jasonojh

  I would like to use Esper to generate episodes of events. I am trying to detect the changes in robot movement during each time period and was wondering what would be the best way of implementation. The rules for generation of episodes from the events would be If the new event time(eg. 7sec, robot A) of a robot is more than 3 sec than the latest event(eg. 3 sec, robot A) of the same robot, the new event belongs to a new episode. Each episode should represent only one robot (eg. 2sec, robotA and 3sec, robotB should output 2 episodes) Input data: Event Time Robot Position 1 1 A 0 2 2 A 1 3 6 A 2 Output data should be: Array[0]={Event 1,Event 2} Array[1]={Event 3} //more than 3 sec Input data: Event Time Robot Position 1 1 A 0 2 2 A 1 3 4 B 0 4 6 A 2 Output data should be: Array[0]={Event 1,Event 2} Array[1]={Event 3} //different robot Array[2]={Event 4} Please help provide suggestions. I have tried using mulitple listeners, one for each robot, to create episodes and it works but I am trying to use a single EPL statement to do it. I have tried win:time_accum(3sec) group by robot but the second example output: Array[0]={Event 1,Event 2, Event 4} Array[1]={Event 3} as the time window is shifted everytime an event comes in, the system still thinks that event 4 is less than 3 sec due to event 3. how do I create a unique time window for each robot? Thank you for your suggestions and any help is greatly appreciated.

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• Transparently surround a component with a link in Wicket

  - by Toni Menzel

  I want to be able to add links on certain items in an ListView. If an items is surrounded by the link or not is up to the code, so its not in the normal page markup. Say i have a markup like this: <div class="column" wicket:id="columnRepeater"> <span wicket:id="column"></span> </div> So essentially, while filling the repeater with a ListView i am able to find a custom renderer for the column component. (not my playingfield). What i want is to add a Link/Ajax Link around the column component. I learned using wicket:border lets you surround additional stuff. Now, the border markup looks like this: <wicket:border> <a wicket:id="link"><wicket:body/></a> </wicket:border> Now, i am a bit puzzled what the Border implementation looks like. Anyone there who can suggest a working java part? I have a couple of "work in progress" solutions but none works. Most questions have to do with usage of component ids. Is the border id = column ? Whats the id of the inner (border body) id then?

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• Best way to build an application based on R?

  - by Prasad Chalasani

  I'm looking for suggestions on how to go about building an application that uses R for analytics, table generation, and plotting. What I have in mind is an application that: displays various data tables in different tabs, somewhat like in Excel, and the columns should be sortable by clicking. takes user input parameters in some dialog windows. displays plots dynamically (i.e. user-input-dependent) either in a tab or in a new pop-up window/frame Note that I am not talking about a general-purpose fron-end/GUI for exploring data with R (like say Rattle), but a specific application. Some questions I'd like to see addressed are: Is an entirely R-based approach even possible ( on Windows ) ? The following passage from the Rattle article in R-Journal intrigues me: It is interesting to note that the first implementation of Rattle actually used Python for implementing the callbacks and R for the statistics, using rpy. The release of RGtk2 allowed the interface el- ements of Rattle to be written directly in R so that Rattle is a fully R-based application If it's better to use another language for the GUI part, which language is best suited for this? I'm looking for a language where it's relatively "painless" to build the GUI, and that also integrates very well with R. From this StackOverflow question How should I do rapid GUI development for R and Octave methods (possibly with Python)? I see that Python + PyQt4 + QtDesigner + RPy2 seems to be the best combo. Is that the consensus ? Anyone have pointers to specific (open source) applications of the type I describe, as examples that I can learn from?

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