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  • Preffered lambda syntax?

    - by Roger Alsing
    I'm playing around a bit with my own C like DSL grammar and would like some oppinions. I've reserved the use of "(...)" for invocations. eg: foo(1,2); My grammar supports "trailing closures" , pretty much like Ruby's blocks that can be passed as the last argument of an invocation. Currently my grammar support trailing closures like this: foo(1,2) { //parameterless closure passed as the last argument to foo } or foo(1,2) [x] { //closure with one argument (x) passed as the last argument to foo print (x); } The reason why I use [args] instead of (args) is that (args) is ambigious: foo(1,2) (x) { } There is no way in this case to tell if foo expects 3 arguments (int,int,closure(x)) or if foo expects 2 arguments and returns a closure with one argument(int,int) - closure(x) So thats pretty much the reason why I use [] as for now. I could change this to something like: foo(1,2) : (x) { } or foo(1,2) (x) -> { } So the actual question is, what do you think looks best? [...] is somewhat wrist unfriendly. let x = [a,b] { } Ideas?

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  • Self-referencing anonymous closures: is JavaScript incomplete?

    - by Tom Auger
    Does the fact that anonymous self-referencing function closures are so prevelant in JavaScript suggest that JavaScript is an incomplete specification? We see so much of this: (function () { /* do cool stuff */ })(); and I suppose everything is a matter of taste, but does this not look like a kludge, when all you want is a private namespace? Couldn't JavaScript implement packages and proper classes? Compare to ActionScript 3, also based on EMACScript, where you get package com.tomauger { import bar; class Foo { public function Foo(){ // etc... } public function show(){ // show stuff } public function hide(){ // hide stuff } // etc... } } Contrast to the convolutions we perform in JavaScript (this, from the jQuery plugin authoring documentation): (function( $ ){ var methods = { init : function( options ) { // THIS }, show : function( ) { // IS }, hide : function( ) { // GOOD }, update : function( content ) { // !!! } }; $.fn.tooltip = function( method ) { // Method calling logic if ( methods[method] ) { return methods[ method ].apply( this, Array.prototype.slice.call( arguments, 1 )); } else if ( typeof method === 'object' || ! method ) { return methods.init.apply( this, arguments ); } else { $.error( 'Method ' + method + ' does not exist on jQuery.tooltip' ); } }; })( jQuery ); I appreciate that this question could easily degenerate into a rant about preferences and programming styles, but I'm actually very curious to hear how you seasoned programmers feel about this and whether it feels natural, like learning different idiosyncrasies of a new language, or kludgy, like a workaround to some basic programming language components that are just not implemented?

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  • Data migration - dangerous or essential?

    - by MRalwasser
    The software development department of my company is facing with the problem that data migrations are considered as potentially dangerous, especially for my managers. The background is that our customers are using a large amount of data with poor quality. The reasons for this is only partially related to our software quality, but rather to the history of the data: Most of them have been migrated from predecessor systems, some bugs caused (mostly business) inconsistencies in the data records or misentries by accident on the customer's side (which our software allowed by error). The most important counter-arguments from my managers are that faulty data may turn into even worse data, the data troubles may awake some managers at the customer and some processes on the customer's side may not work anymore because their processes somewhat adapted to our system. Personally, I consider data migrations as an integral part of the software development and that data migration can been seen to data what refactoring is to code. I think that data migration is an essential for creating software that evolves. Without it, we would have to create painful software which somewhat works around a bad data structure. I am asking you: What are your thoughts to data migration, especially for the real life cases and not only from a developer's perspecticve? Do you have any arguments against my managers opinions? How does your company deal with data migrations and the difficulties caused by them? Any other interesting thoughts which belongs to this topics?

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  • Nested entities in Google App Engine. Do I do it right?

    - by Aleksandr Makov
    Trying to make most of the GAE Datastore entities concept, but some doubts drill my head. Say I have the model: class User(ndb.Model): email = ndb.StringProperty(indexed=True) password = ndb.StringProperty(indexed=False) first_name = ndb.StringProperty(indexed=False) last_name = ndb.StringProperty(indexed=False) created_at = ndb.DateTimeProperty(auto_now_add=True) @classmethod def key(cls, email): return ndb.Key(User, email) @classmethod def Add(cls, email, password, first_name, last_name): user = User(parent=cls.key(email), email=email, password=password, first_name=first_name, last_name=last_name) user.put() UserLogin.Record(email) class UserLogin(ndb.Model): time = ndb.DateTimeProperty(auto_now_add=True) @classmethod def Record(cls, user_email): login = UserLogin(parent=User.key(user_email)) login.put() And I need to keep track of times of successful login operations. Each time user logs in, an UserLogin.Record() method will be executed. Now the question — do I make it right? Thanks. EDIT 2 Ok, used the typed arguments, but then it raised this: Expected Key instance, got User(key=Key('User', 5418393301680128), created_at=datetime.datetime(2013, 6, 27, 10, 12, 25, 479928), email=u'[email protected]', first_name=u'First', last_name=u'Last', password=u'password'). It's clear to understand, but I don't get why the docs are misleading? They implicitly propose to use: # Set Employee as Address entity's parent directly... address = Address(parent=employee) But Model expects key. And what's worse the parent=user.key() swears that key() isn't callable. And I found out the user.key works. EDIT 1 After reading the example form the docs and trying to replicate it — I got type error: TypeError('Model constructor takes no positional arguments.'). This is the exacto code used: user = User('[email protected]', 'password', 'First', 'Last') user.put() stamp = UserLogin(parent=user) stamp.put() I understand that Model was given the wrong argument, BUT why it's in the docs?

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  • Understanding and memorizing git rebase parameters

    - by Robert Dailey
    So far the most confusing portion of git is rebasing onto another branch. Specifically, it's the command line arguments that are confusing. Each time I want to rebase a small piece of one branch onto the tip of another, I have to review the git rebase documentation and it takes me about 5-10 minutes to understand what each of the 3 main arguments should be. git rebase <upstream> <branch> --onto <newbase> What is a good rule of thumb to help me memorize what each of these 3 parameters should be set to, given any kind of rebase onto another branch? Bear in mind I have gone over the git-rebase documentation again, and again, and again, and again (and again), but it's always difficult to understand (like a boring scientific white-paper or something). So at this point I feel I need to involve other people to help me grasp it. My goal is that I should never have to review the documentation for these basic parameters. I haven't been able to memorize them so far, and I've done a ton of rebases already. So it's a bit unusual that I've been able to memorize every other command and its parameters so far, but not rebase with --onto.

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  • Can DVCSs enforce a specific workflow?

    - by dukeofgaming
    So, I have this little debate at work where some of my colleagues (which are actually in charge of administrating our Perforce instance) say that workflows are strictly a process thing, and that the tools that we use (in this case, the version control system) have no take on it. In otherwords, the point that they make is that workflows (and their execution) are tool-agnostic. My take on this is that DVCSs are better at encouraging people in more flexible and well-defined ways, because of the inherent branching occurring in the background (anonymous branches), and that you can enforce workflows through the deployment model you establish (e.g. pull requests through repository management, dictator/liutenant roles with their machines setup as servers, etc.) I think in CVCSs you have to enforce workflows through policies and policing, because there is only one way to share the code, while in DVCSs you just go with the flow based on the infrastructure/permissions that were setup for you. Even when I have provided the earlier arguments, I'm still unable to fully convince them. Am I saying something the wrong way?, if not, what other arguments or examples do you think would be useful to convince them? Edit: The main workflow we have been focusing on, because it makes sense to both sides is the Dictator/Lieutenants workflow: My argument for this particular workflow is that there is no pipeline in a CVCS (because there is just sharing work in a centralized way), whereas there is an actual pipeline in DVCSs depending on how you deploy read/write permissions. Their argument is that this workflow can be done through branching, and while they do this in some projects (due to policy/policing) in other projects they forbid developers from creating branches.

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  • How to market R at your institute?

    - by ran2
    Okay, I admit there are lots of threads R vs. something. The strengths of R are obvious to most people here. Still though advertising R in an environment that has been preferring various kinds of other software for quite some time is not easy. Moreover, even in the limited time I´ve been dealing with R, it improved so dramatically that I would mention things among its strengths that I would not have listed when I started my personal R-evolution. So, what I am trying to do here is to collect the most recent and striking arguments that can be put in nutshell and be presented easily. What I got on my list so far is: the Springer useR series ggplot2 and its documentation open source CRAN Rapache rcpp rsocket What can you add to this list? SO threads are also very welcome as answers. EDIT: so far, though indeed very helpful, most answers are arguments (pros) why one would want to use R. Do you have some specific hints that I could include in some kind of overview presentation? EDIT2: I wanted to add this link about R's future to the list...

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  • Preferred lambda syntax?

    - by Roger Alsing
    I'm playing around a bit with my own C like DSL grammar and would like some oppinions. I've reserved the use of "(...)" for invocations. eg: foo(1,2); My grammar supports "trailing closures" , pretty much like Ruby's blocks that can be passed as the last argument of an invocation. Currently my grammar support trailing closures like this: foo(1,2) { //parameterless closure passed as the last argument to foo } or foo(1,2) [x] { //closure with one argument (x) passed as the last argument to foo print (x); } The reason why I use [args] instead of (args) is that (args) is ambigious: foo(1,2) (x) { } There is no way in this case to tell if foo expects 3 arguments (int,int,closure(x)) or if foo expects 2 arguments and returns a closure with one argument(int,int) - closure(x) So thats pretty much the reason why I use [] as for now. I could change this to something like: foo(1,2) : (x) { } or foo(1,2) (x) -> { } So the actual question is, what do you think looks best? [...] is somewhat wrist unfriendly. let x = [a,b] { } Ideas?

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  • C++ and SDL Trouble Creating a STL Vector of a Game Object

    - by Jackson Blades
    I am trying to create a Space Invaders clone using C++ and SDL. The problem I am having is in trying to create Waves of Enemies. I am trying to model this by making my Waves a vector of 8 Enemy objects. My Enemy constructor takes two arguments, an x and y offset. My Wave constructor also takes two arguments, an x and y offset. What I am trying to do is have my Wave constructor initialize a vector of Enemies, and have each enemy given a different x offset so that they are spaced out appropriately. Enemy::Enemy(int x, int y) { box.x = x; box.y = y; box.w = ENEMY_WIDTH; box.h = ENEMY_HEIGHT; xVel = ENEMY_WIDTH / 2; } Wave::Wave(int x, int y) { box.x = x; box.y = y; box.w = WAVE_WIDTH; box.y = WAVE_HEIGHT; xVel = (-1)*ENEMY_WIDTH; yVel = 0; std::vector<Enemy> enemyWave; for (int i = 0; i < enemyWave.size(); i++) { Enemy temp(box.x + ((ENEMY_WIDTH + 16) * i), box.y); enemyWave.push_back(temp); } } I guess what I am asking is if there is a cleaner, more elegant way to do this sort of initialization with vectors, or if this is right at all. Any help is greatly appreciated.

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  • The idea of functionN in Scala / Functionaljava

    - by Luke Murphy
    From brain driven development It turns out, that every Function you’ll ever define in Scala, will become an instance of an Implementation which will feature a certain Function Trait. There is a whole bunch of that Function Traits, ranging from Function1 up to Function22. Since Functions are Objects in Scala and Scala is a statically typed language, it has to provide an appropriate type for every Function which comes with a different number of arguments. If you define a Function with two arguments, the compiler picks Function2 as the underlying type. Also, from Michael Froh's blog You need to make FunctionN classes for each number of parameters that you want? Yes, but you define the classes once and then you use them forever, or ideally they're already defined in a library (e.g. Functional Java defines classes F, F2, ..., F8, and the Scala standard library defines classes Function1, ..., Function22) So we have a list of function traits (Scala), and a list of interfaces (Functional-java) to enable us to have first class funtions. I am trying to understand exactly why this is the case. I know, in Java for example, when I write a method say, public int add(int a, int b){ return a + b; } That I cannot go ahead and write add(3,4,5); ( error would be something like : method add cannot be applied to give types ) We simply have to define an interface/trait for functions with different parameters, because of static typing?

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  • Depending on fixed version of a library and ignore its updates

    - by Moataz Elmasry
    I was talking to a technical boss yesterday. Its about a project in C++ that depends on opencv and he wanted to include a specific opencv version into the svn and keep using this version ignoring any updates which I disagreed with.We had a heated discussion about that. His arguments: Everything has to be delivered into one package and we can't ask the client to install external libraries. We depend on a fixed version so that new updates of opencv won't screw our code. We can't guarantee that within a version update, ex from 3.2.buildx to 3.2.buildy. Buildy the function signatures won't change. My arguments: True everything has to be delivered to the client as one package,but that's what build scripts are for. They download the external libraries and create a bundle. Within updates of the same version 3.2.buildx to 3.2.buildy its impossible that a signature change, unless it is a really crappy framework, which isn't the case with opencv. We deprive ourselves from new updates and features of that library. If there's a bug in the version we took, and even if there's a bug fix later, we won't be able to get that fix. Its simply ineffiecient and anti design to depend on a certain version/build of an external library as it makes our project difficult in the future to adopt to new changes. So I'd like to know what you guys think. Does it really make sense to include a specific version of external library in our svn and keep using it ignoring all updates?

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  • How to convince an employer to move to VB.Net for new development?

    - by Dabblernl
    Some history:For the last six months I have been employed at a small firm with just three programmers, my employer among them. The firm maintains two programs written in VB6. I am asssigned as the lead programmer to one of these. In the last six months I did some maintenance and bug hunting, but created some new functionality too. I had an interview last december, which was favorable, and my contract was prolonged. I am very happy with this course of events as I only obtained a .Net certification a year ago and have no other qualifications (in the field of coding, that is). It is my strong opinion that, while migration of the existing program to .Net is advisable, it is paramount that from now on the new functionality should be written in VB.Net class libraries. After some study I found out how simple it is to integrate .Net class libraries into the VB6 development environment and how easy it is to add their functionality to existing installations by using application manifests. So, I have decided that now is the moment to roll up my sleeves and try and convince my employer that he should let me develop new code in VB.Net, using VB6 for maintenance only. We get along quite well, but I think I am going to need all the ammunition I can get to convince him. Any arguments, preferably backed up up ones, are very welcome, even arguments to dissuade me ;-)

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  • Call DB Stored Procedure using @NamedStoredProcedureQuery Injection

    - by anwilson
    Oracle Database Stored Procedure can be called from EJB business layer to perform complex DB specific operations. This approach will avoid overhead from frequent network hits which could impact end-user result. DB Stored Procedure can be invoked from EJB Session Bean business logic using org.eclipse.persistence.queries.StoredProcedureCall API. Using this approach requires more coding to handle the Session and Arguments of the Stored Procedure, thereby increasing effort on maintenance. EJB 3.0 introduces @NamedStoredProcedureQuery Injection to call Database Stored Procedure as NamedQueries. This blog will take you through the steps to call Oracle Database Stored Procedure using @NamedStoredProcedureQuery.EMP_SAL_INCREMENT procedure available in HR schema will be used in this sample.Create Entity from EMPLOYEES table.Add @NamedStoredProcedureQuery above @NamedQueries to Employees.java with definition as given below - @NamedStoredProcedureQuery(name="Employees.increaseEmpSal", procedureName = "EMP_SAL_INCREMENT", resultClass=void.class, resultSetMapping = "", returnsResultSet = false, parameters = { @StoredProcedureParameter(name = "EMP_ID", queryParameter = "EMPID"), @StoredProcedureParameter(name = "SAL_INCR", queryParameter = "SALINCR")} ) Observe how Stored Procedure's arguments are handled easily in  @NamedStoredProcedureQuery using @StoredProcedureParameter.Expose Entity Bean by creating a Session Facade.Business method need to be added to Session Bean to access the Stored Procedure exposed as NamedQuery. public void salaryRaise(Long empId, Long salIncrease) throws Exception { try{ Query query = em.createNamedQuery("Employees.increaseEmpSal"); query.setParameter("EMPID", empId); query.setParameter("SALINCR", salIncrease); query.executeUpdate(); } catch(Exception ex){ throw ex; } } Expose business method through Session Bean Remote Interface. void salaryRaise(Long empId, Long salIncrease) throws Exception; Session Bean Client is required to invoke the method exposed through remote interface.Call exposed method in Session Bean Client main method. final Context context = getInitialContext(); SessionEJB sessionEJB = (SessionEJB)context.lookup("Your-JNDI-lookup"); sessionEJB.salaryRaise(new Long(200), new Long(1000)); Deploy Session BeanRun Session Bean Client.Salary of Employee with Id 200 will be increased by 1000.

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  • How to add an onclick event to a joint.js element?

    - by ahalbert
    I have a joint.js element in a DAG, and would like to be able to trigger an event by clicking on it. I could use $(selector).click(...) to do it, but I was wondering if there was a joint.js specific way of handling it, since that would probobly be better. One event I decided was a candidate for onclick was 'batch:stop' My code: var variable = new joint.shapes.basic.Rect({ name : label, id: label, onclick : function () {alert("hello");}, size: { width: width, height: height }, attrs: { text: { text: label, 'font-size': letterSize, 'font-family': 'monospace' }, rect: { fill : fillColor, width: width, height: height, rx: 5, ry: 5, stroke: '#555' } } }); variable.on('batch:stop', function (element) {alert(""); toggleEvidence(element.name);}); return variable; How should I add an onclick event?

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  • Xcode is not calling asp.net webservice

    - by vaibhav
    I have oracle database and using webservice i want to insert some records in to it So i created webservice in asp.net as follows public bool PickPill(string Me_id, string Mem_device_id, string Test_datetime, string Creation_id, string PillBayNo) { string Hed_seq_id = Hed_seq_Id(); bool ResultHED = InsHealthEData(Hed_seq_id, Mem_device_id, Me_id, Test_datetime, Creation_id); bool ResultHET = InsHealthETest(Hed_seq_id, PillBayNo, Test_datetime, Creation_id); if (ResultHED == ResultHET == true) return true; else return false; } this function did all data insertion trick for me i tested this service on the local mechine with ip address http:72.44.151.178/PickPillService.asmx then, I see an example on how to attach asp.net web service to iphone apps http://www.devx.com/wireless/Article/43209/0/page/4 then i created simillar code in xcode which has 2 files ConsumePillServiceViewController.m ConsumePillServiceViewController.h file Now, Using Designer of xcode i created 5 textboxes(Me_id,Mem_device_id,Test_datetime,Creation_id,PillBayNo) with all parameters hardcode as our service demands then modify my ConsumePillServiceViewController.h file as follows @interface ConsumePillServiceViewController : UIViewController { //---outlets--- IBOutlet UITextField *Me_id; IBOutlet UITextField *Mem_device_id; IBOutlet UITextField *Test_datetime; IBOutlet UITextField *Creation_id; IBOutlet UITextField *PillBayNo; //---web service access--- NSMutableData *webData; NSMutableString *soapResults; NSURLConnection *conn; } @property (nonatomic, retain) UITextField *Me_id; @property (nonatomic, retain) UITextField *Mem_device_id; @property (nonatomic, retain) UITextField *Test_datetime; @property (nonatomic, retain) UITextField *Creation_id; @property (nonatomic, retain) UITextField *PillBayNo; - (IBAction)buttonClicked:(id)sender; @end and ConsumePillServiceViewController.m as follows import "ConsumePillServiceViewController.h" @implementation ConsumePillServiceViewController @synthesize Me_id; @synthesize Mem_device_id; @synthesize Test_datetime; @synthesize Creation_id; @synthesize PillBayNo; (IBAction)buttonClicked:(id)sender { NSString *soapMsg = @"" "" "" ""; NSString *smMe_id= [soapMsg stringByAppendingString: [NSString stringWithFormat: @"%@",Me_id.text]]; NSString *smMem_device_id= [smMe_id stringByAppendingString: [NSString stringWithFormat: @"%@",Mem_device_id.text]]; NSString *smTest_datetime= [smMem_device_id stringByAppendingString: [NSString stringWithFormat: @"%@",Test_datetime.text]]; NSString *smCreation_id= [smTest_datetime stringByAppendingString: [NSString stringWithFormat: @"%@",Creation_id.text]]; NSString *smPillBayNo= [smCreation_id stringByAppendingString: [NSString stringWithFormat: @"%@",PillBayNo.text]]; NSString *smRestMsg= [smPillBayNo stringByAppendingString: @"" "" ""]; soapMsg=smRestMsg; //---print it to the Debugger Console for verification--- NSLog(soapMsg); NSURL *url = [NSURL URLWithString: //create a URL load request object using instances : @"http://72.44.151.178/PickPillService.asmx"];//of the NSMutableURLRequest and NSURL objects NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:url]; //opulate the request object with the various headers, such as Content-Type, SOAPAction, and Content-Length. //You also set the HTTP method and HTTP body NSString *msgLength = [NSString stringWithFormat:@"%d", [soapMsg length]]; [req addValue:@"text/xml; charset=utf-8" forHTTPHeaderField:@"Content-Type"]; [req addValue:@"http://tempuri.org/PickPill" forHTTPHeaderField:@"SOAPAction"]; [req addValue:msgLength forHTTPHeaderField:@"Content-Length"]; //---set the HTTP method and body--- [req setHTTPMethod:@"POST"]; [req setHTTPBody: [soapMsg dataUsingEncoding:NSUTF8StringEncoding]]; conn = [[NSURLConnection alloc] initWithRequest:req delegate:self]; //establish the connection with the web service, if (conn) { //you use the NSURLConnection class together with the request object just created webData = [[NSMutableData data] retain];//webData object use to receive incoming data from the web service } }//End of button clicked event -(void) connection:(NSURLConnection *) connection //Recive response didReceiveResponse:(NSURLResponse *) response { [webData setLength: 0]; } -(void) connection:(NSURLConnection *) connection //Repeative call method and append data to webData didReceiveData:(NSData *) data { [webData appendData:data]; } -(void) connection:(NSURLConnection *) connection//If error occure error should be displayed didFailWithError:(NSError *) error { [webData release]; [connection release]; } -(void) connectionDidFinishLoading:(NSURLConnection *) connection { NSLog(@"DONE. Received Bytes: %d", [webData length]); NSString *theXML = [[NSString alloc] initWithBytes: [webData mutableBytes] length:[webData length] encoding:NSUTF8StringEncoding]; //---shows the XML--- NSLog(theXML); [connection release]; [webData release]; } (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc that aren't in use. } (void)viewDidUnload { // Release any retained subviews of the main view. // e.g. self.myOutlet = nil; } (void)dealloc { [Me_id release]; [Creation_id release]; [Mem_device_id release]; [Test_datetime release]; [PillBayNo release]; [soapResults release]; [super dealloc]; } @end I did all things as shown in the website and when i built application it successfully built but in the debuggin window i see (gdb) continue 2010-03-17 09:09:54.595 ConsumePillService[6546:20b] A00000004303101103/13/2010 07:34:38Hboxdata2 (gdb) continue (gdb) continue (gdb) continue 2010-03-17 09:10:05.411 ConsumePillService[6546:20b] DONE. Received Bytes: 476 2010-03-17 09:10:05.412 ConsumePillService[6546:20b] soap:ServerServer was unable to process request. ---> One or more errors occurred during processing of command. ORA-00936: missing expression It should return me true if all things are ok What is this ORA-00936 error all about as it is not releted with webservice Please help me solving this problem Thanks in advance, Vaibhav Deshpande

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  • C# Dictionary as a ListBox.DataSource

    - by Steve H.
    I am trying to bind a dictionary as a DataSource to a ListBox. The solution in How to bind a dicationary to a ListBox in winforms will not work for me because my dictionary is a class-level variable and not a method-level variable, so I can not use var. When you put a class-level variable into new BindingSource(...) with null as the second argument I get an ArgumentNull exception. How do I bind a class-level dictionary as a data source for a list box? I don't like the List< KeyValuePair< string, string work-around becuase Where(...) and First(...) are ugly, complicated, and confusing compared to TryGetValue(...) and other Dictionary functionality.

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  • Optimized Image Loading in a UIScrollView

    - by Michael Gaylord
    I have a UIScrollView that has a set of images loaded side-by-side inside it. You can see an example of my app here: http://www.42restaurants.com. My problem comes in with memory usage. I want to lazy load the images as they are about to appear on the screen and unload images that aren't on screen. As you can see in the code I work out at a minimum which image I need to load and then assign the loading portion to an NSOperation and place it on an NSOperationQueue. Everything works great apart from a jerky scrolling experience. I don't know if anyone has any ideas as to how I can make this even more optimized, so that the loading time of each image is minimized or so that the scrolling is less jerky. - (void)scrollViewDidScroll:(UIScrollView *)scrollView{ [self manageThumbs]; } - (void) manageThumbs{ int centerIndex = [self centerThumbIndex]; if(lastCenterIndex == centerIndex){ return; } if(centerIndex >= totalThumbs){ return; } NSRange unloadRange; NSRange loadRange; int totalChange = lastCenterIndex - centerIndex; if(totalChange > 0){ //scrolling backwards loadRange.length = fabsf(totalChange); loadRange.location = centerIndex - 5; unloadRange.length = fabsf(totalChange); unloadRange.location = centerIndex + 6; }else if(totalChange < 0){ //scrolling forwards unloadRange.length = fabsf(totalChange); unloadRange.location = centerIndex - 6; loadRange.length = fabsf(totalChange); loadRange.location = centerIndex + 5; } [self unloadImages:unloadRange]; [self loadImages:loadRange]; lastCenterIndex = centerIndex; return; } - (void) unloadImages:(NSRange)range{ UIScrollView *scrollView = (UIScrollView *)[[self.view subviews] objectAtIndex:0]; for(int i = 0; i < range.length && range.location + i < [scrollView.subviews count]; i++){ UIView *subview = [scrollView.subviews objectAtIndex:(range.location + i)]; if(subview != nil && [subview isKindOfClass:[ThumbnailView class]]){ ThumbnailView *thumbView = (ThumbnailView *)subview; if(thumbView.loaded){ UnloadImageOperation *unloadOperation = [[UnloadImageOperation alloc] initWithOperableImage:thumbView]; [queue addOperation:unloadOperation]; [unloadOperation release]; } } } } - (void) loadImages:(NSRange)range{ UIScrollView *scrollView = (UIScrollView *)[[self.view subviews] objectAtIndex:0]; for(int i = 0; i < range.length && range.location + i < [scrollView.subviews count]; i++){ UIView *subview = [scrollView.subviews objectAtIndex:(range.location + i)]; if(subview != nil && [subview isKindOfClass:[ThumbnailView class]]){ ThumbnailView *thumbView = (ThumbnailView *)subview; if(!thumbView.loaded){ LoadImageOperation *loadOperation = [[LoadImageOperation alloc] initWithOperableImage:thumbView]; [queue addOperation:loadOperation]; [loadOperation release]; } } } } EDIT: Thanks for the really great responses. Here is my NSOperation code and ThumbnailView code. I tried a couple of things over the weekend but I only managed to improve performance by suspending the operation queue during scrolling and resuming it when scrolling is finished. Here are my code snippets: //In the init method queue = [[NSOperationQueue alloc] init]; [queue setMaxConcurrentOperationCount:4]; //In the thumbnail view the loadImage and unloadImage methods - (void) loadImage{ if(!loaded){ NSString *filename = [NSString stringWithFormat:@"%03d-cover-front", recipe.identifier, recipe.identifier]; NSString *directory = [NSString stringWithFormat:@"RestaurantContent/%03d", recipe.identifier]; NSString *path = [[NSBundle mainBundle] pathForResource:filename ofType:@"png" inDirectory:directory]; UIImage *image = [UIImage imageWithContentsOfFile:path]; imageView = [[ImageView alloc] initWithImage:image andFrame:CGRectMake(0.0f, 0.0f, 176.0f, 262.0f)]; [self addSubview:imageView]; [self sendSubviewToBack:imageView]; [imageView release]; loaded = YES; } } - (void) unloadImage{ if(loaded){ [imageView removeFromSuperview]; imageView = nil; loaded = NO; } } Then my load and unload operations: - (id) initWithOperableImage:(id<OperableImage>) anOperableImage{ self = [super init]; if (self != nil) { self.image = anOperableImage; } return self; } //This is the main method in the load image operation - (void)main { [image loadImage]; } //This is the main method in the unload image operation - (void)main { [image unloadImage]; }

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  • Mean filter in MATLAB without loops or signal processing toolbox

    - by Doresoom
    I need to implement a mean filter on a data set, but I don't have access to the signal processing toolbox. Is there a way to do this without using a for loop? Here's the code I've got working: x=0:.1:10*pi; noise=0.5*(rand(1,length(x))-0.5); y=sin(x)+noise; %generate noisy signal a=10; %specify moving window size my=zeros(1,length(y)-a); for n=a/2+1:length(y)-a/2 my(n-a/2)=mean(y(n-a/2:n+a/2)); %calculate mean for each window end mx=x(a/2+1:end-a/2); %truncate x array to match plot(x,y) hold on plot(mx,my,'r')

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  • Move to next page if Table can not adjust in current page using iText

    - by Saurabh
    I am generating a PDF report using iText. The report is having four parts as - Project Info1 (A PDF Table of variable height) Project Info2 (A PDF Table of variable height) Requestor Info (A PDF Table of Fixed height) Location Info (A PDF Table of Fixed height) The top two information are of variable height and they can acquire certain pages. The other two are of fixed size which comes at last. I want to move the last (one or both) boxes to the next page if there is no space available to fit those boxes in current page. If space for one box is available then place one to the current page and move other box to the next table. Is there way to decide this?

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  • Preventing closure compiler from renaming certain variables

    - by phidah
    I have a javascript file with a global object that must not be renamed (_gat from the Google Analytics async tracker). This object must not be renamed by the Google Closure Compiler as Google Analytics looks for a variable with this specific name. I've looked into the Javascript Doc notations that are mentioned: http://code.google.com/closure/compiler/docs/js-for-compiler.html - However, I cannot find anything regarding the "protection" of a variable. The problem exists no matter if I use simple or advanced compilation. How can I ensure that the _gat variable is not renamed?

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  • Common lisp error: "should be lambda expression"

    - by Zachary
    I just started learning Common Lisp a few days ago, and I'm trying to build a function that inserts a number into a tree. I'm getting an error, * - SYSTEM::%EXPAND-FORM: (CONS NIL LST) should be a lambda expression From googling around, it seems like this happens when you have too many sets of parenthesis, but after looking at this for an hour or so and changing things around, I can't figure out where I could be doing this. This is the code where it's happening: (defun insert (lst probe) (cond ((null lst) (cons probe lst)) ((equal (length lst) 1) (if (<= probe (first lst)) (cons probe lst) (append lst (list probe)))) ((equal (length lst) 2) ((cons nil lst) (append lst nil) (insertat nil lst 3) (cond ((<= probe (second lst)) (insert (first lst) probe)) ((> probe (fourth lst)) (insert (fifth lst) probe)) (t (insert (third lst) probe))))))) I'm pretty sure it's occurring after the ((equal (length lst) 2), where the idea is to insert an empty list into the existing list, then append an empty list onto the end, then insert an empty list into the middle.

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  • Check if a String is a double or an int?

    - by user69514
    I have a string for a Date in the form mm/dd, and I need to check if either the month or day was entered as a double public Date(String dateStr){ int slash = 0; //check slash is present try{ slash = dateStr.indexOf('/'); }catch(StringIndexOutOfBoundsException e){ error = "Invalid date format: " + dateStr; } //check if month is a number try{ month = Integer.parseInt(dateStr.substring(0, slash)); //day = Integer.parseInt(dateStr.substring(slash + 1, dateStr.length())); } catch(NumberFormatException e){ System.out.println("Invalid format for input string: " + dateStr.substring(0, slash)); } //check if day is a number try{ day = Integer.parseInt(dateStr.substring(slash + 1, dateStr.length())); } catch(NumberFormatException e){ System.out.println("Invalid format for input string: " + dateStr.substring(slash + 1, dateStr.length())); } //check if month was entered as a double }

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  • Java 64bit install throwing non compatible 64bit error in 64bit Windows 7

    - by ThunderWolf
    JRE and JDK 64bit install executable are throwing a non compatible win32 error: jre_7u1_windows-x64bit.exe is not a valid Win32 application. I thought this could be a system environment variable problem, but from what I can tell it is not, the variable PROCESSOR_ARCHITECTURE is set as: AMD64 and the variable PROCESSOR_IDENTIFIER is set as: Intel64 Family 6 Model 37 Stepping 5, GenuineIntel I am not sure what variables the installer reads from if any. I have tried java 6 installer and the same thing. I can install other programs designed for a 64bit architecture and I have looked at Control PanelSystem and SecuritySystem: which is in fact "System type: 64-bit Operating System".

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  • java cosine similarity problem

    - by agazerboy
    Hi again :) I developed some java program to calculate cosine similarity on the basis of TF*IDF. It worked very well. But there is one problem.... :( for example: If I have following two matrix and I want to calculate cosine similarity it does not work as rows are not same in length doc 1 1 2 3 4 5 6 doc 2 1 2 3 4 5 6 7 8 5 2 4 9 if rows and colums are same in length then my program works very well but it does not if rows and columns are not in same length. Any tips ???

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  • general database modeling and django specific modeling

    - by Shreko
    I'm wondering what is the best way to model something like the following. Lets say my company sells metal bars (parameters/fields are: length, profile_type, quantity etc.) of different profiles, where profiles may be pipe(pipe_diameter, wall_thickness) or hollow_rectangle(base, height, wall_thickness), or maybe some other profile with different parameters. Lets say maximum number of profiles would be 12, each profile having between 2-5 parameters. Should everything be in a single table like table_bars: id, length, quantity, profile_type, pipe_diameter, wall_thickness, base, height, etc.) where profile type would be (pipe, rectangle etc.) or should every shape have its own table with its own parameters and in table_bars keep only id, length, quantity profile_type and profile_id) and are there any django specific issues is multiple tables are the best answer? Thanks

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