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• I need help solving a rather weird error in a WCF service.

  - by Moulde

  Hi.. I have a solution that contains three projects. A main project with my MVC app, a silverlight application and a (silverlight enabled) WCF service project. In my silverlight project i have made a Service Reference to my WCF service. And i pretty much got that working. In my WCF service i have a method that returns an Book object, which got some random fields like title, date etc. In the book class, i have a ICollection field that contains a list of events. The book class is generated using entity framework 4.0, and Lazy Loading is enabled. If i in my getBook(int id) method return a book with the events field not initialized, it works as a charm. But if i initialize the field, i'm getting this error. The server did not provide a meaningful reply; this might be caused by a contract mismatch, a premature session shutdown or an internal server error. I have a few ideas why that is happening, and while writing this i just got another one. The wcf service somehow threw away the reference to the event class. That would be very weird since i have a reference between my main mvc app (with the models) and my WCF service. Since i have enabled lazy loading in EF 4.0, i suspect that it may be the thing generating the error. But i'm not sure why that would be, because i'm not in any way accessing that field. I could understand that i may not be able to access the events field after i recive the object in my silverlight application since the connection between the book object and the entity framework is like broken. Did i mention that Lazy Loading is enabled on my EF instance? And there is no inner exception in the thrown exception. Thanks in advance. Malte Baden Hansen

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• Getting all the classes in project and their packages from CodeRush extension

  - by drasto

  I've spent some time trying to find a way CodeRush could add using when it finds undeclared element that is in the fact class name with no using added. The solution suggested in this answer to my question (Refactor_resolve) does not work (bugged?). In a process I found out that writing plug-ins for CodeRush is easy, so I decided to code this functionality myself (and share it). I'd only implement a CodeProvider (like in this tutorial). The only thinks I need to do the job are answers to this questions: At the start up of my plugin I need to get a list (set, map, whatever) of all classes and their packages. This means all the classes(interfaces...) and their packages in project, and within all referenced libraries. And I also need to receive updated on this (when user adds reference, creates new class). Can I get this from some CodeRush classes or maybe VS interface available from CodeProvider class? How do I add created CodeProvider to the pop-up that is shown when user hovers over an Issue?

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• How to implement a grapher in C#

  - by iansinke

  So I'm writing a graphing calculator. So far I have a semi-functional grapher, however, I'm having a hard time getting a good balance between accurate graphs and smooth looking curves. The current implementation (semi-pseudo-code) looks something like this: for (float i = GraphXMin; i <= GraphXMax; i++) { PointF P = new PointF(i, EvaluateFunction(Function, i) ListOfPoints.Add(P) } Graphics.DrawCurve(ListOfPoints) The problem with this is since it only adds a point at every integer value, graphs end up distorted when their turning points don't fall on integers (e.g. sin(x)^2). I tried incrementing i by something smaller (like 0.1), which works, but the graph looks very rough. I am using C# and GDI+. I have SmoothingMethod set to AntiAlias, so that's not the problem, as you can see from the first graph. Is there some sort of issue with drawing curves with a lot of points? Should the points perhaps be positioned exactly on pixels? I'm sure some of you have worked on something very similar before, so any suggestions? While you're at it, do you have any suggestions for graphing functions with asymptotes? e.g. 1/x^2 P.S. I'm not looking for a library that does all this - I want to write it myself.

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• Noise with multi-threaded raytracer

  - by herber88

  This is my first multi-threaded implementation, so it's probably a beginners mistake. The threads handle the rendering of every second row of pixels (so all rendering is handled within each thread). The problem persists if the threads render the upper and lower parts of the screen respectively. Both threads read from the same variables, can this cause any problems? From what I've understood only writing can cause concurrency problems... Can calling the same functions cause any concurrency problems? And again, from what I've understood this shouldn't be a problem... The only time both threads write to the same variable is when saving the calculated pixel color. This is stored in an array, but they never write to the same indices in that array. Can this cause a problem? Multi-threaded rendered image (Spam prevention stops me from posting images directly..) Ps. I use the exactly same implementation in both cases, the ONLY difference is a single vs. two threads created for the rendering.

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• Calculating distance between two X,Y coordinates

  - by Umopepisdn

  I am writing a tool for a game that involves calculating the distance between two coordinates on a spherical plane 500 units across. That is, [0,0] through [499,499] are valid coordinates, and [0,0] and [499,499] are also right next to each other. Currently, in my application, I am comparing the distance between a city with an [X,Y] location respective to the user's own [X,Y] location, which they have configured in advance. To do this, I found this algorithm, which kind of works: Math.sqrt ( dx * dx + dy * dy ); Because sorting a paged list by distance is a useful thing to be able to do, I implemented this algorithm in a MySQL query and have made it available to my application using the following part of my SELECT statement: SQRT( POW( ( ".strval($sourceX)." - cityX ) , 2 ) + POW( ( ".strval($sourceY)." - cityY ) , 2 ) ) AS distance This works fine for many calculations, but does not take into account the fact that [0,0] and [499,499] are kitty-corner to one another. Is there any way I can tweak this algorithm to generate an accurate distance, given that 0 and 499 are adjacent? Thanks, -Umo

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• How can I identify an element from a list within another list

  - by Alex

  I have been trying to make a block of code that finds the index of the largest bid for each item. Then I was going to use the index as a way to identify the person who paid that much moneys name. However no matter what i try I can't link the person and what they have gained from the auction together. Here is the code I have been writing: It has to be able to work with any information inputted def sealedBids(): n = int(input('\nHow many people are in the group? ')) z = 0 g = [] s = [] b = [] f = [] w = []#goes by number of items q = [] while z < n: b.append([]) z = z + 1 z = 0 while z < n: g.append(input('Enter a bidders name: ')) z = z + 1 z = 0 i = int(input('How many items are being bid on?')) while z < i: s.append(input('Enter the name of an item: ')) w.append(z) z = z + 1 z = 0 for j in range(n):#specifies which persons bids your taking for k in range(i):#specifies which item is being bid on b[j].append(int(input('How much money has {0} bid on the {1}? '.format(g[j], s[k])))) print(' ') for j in range(n):#calculates fair share f.append(sum(b[j])/n) for j in range(i):#identifies which quantity of money was the largest for each item for k in range(n): if w[j] < b[k][j]: w[j] = b[k][j] q.append(k) any advice is much appreciated.

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• Why is short project lifetime and other situation-specific reasons used to excuse crappy code? [clos

  - by sharptooth

  Every now and then (including on SO) people say things implying that "if the project is short lived you can leave obvious defects there" or "that memory leak only accounts for 100 bytes per whole program lifetime and could be left". Now in my practice I always reuse company-owned code to the greatest extent I can. Like if I need something and I can find it in the company codebase I take it from there and reuse or adapt. This means that any crappy code will be reused as well and I might notice or not notice defects therein. So the defect in some "test we only need for a month" can slip into a proram we ship to customers. And a leak that "only accounted for 100 bytes per lifetime" now could account for 100 bytes 10 times per second in a server application intended to run for months. That's why I don't understand why excuses like that are offered. Is our compamy the only one having a source control? Or are we the only company that requires writing human-readable code? Could anyone shed a light on why people seriously offer such excuses?

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• object not getting released in iphone

  - by Jaimin

  i m writing this code in my code to store the data in database.. Search *objSearchDetail = [[Search alloc] init]; objSearchDetail = [xmlResponseDetail objectAtIndex:i]; sql = "INSERT INTO tblsearchdetail(tblrecentsearch_id,name,address,email,url,street,postcode,city,telephone,mobile) VALUES(?,?,?,?,?,?,?,?,?,?)"; returnValue = sqlite3_prepare_v2(database, sql, -1, &insertStatement, NULL); if(returnValue == SQLITE_OK){ sqlite3_bind_int(insertStatement, 1, intLastRecentSearchId); sqlite3_bind_text(insertStatement, 2, [objSearchDetail.strName UTF8String], -1,SQLITE_TRANSIENT); sqlite3_bind_text(insertStatement, 3, [objSearchDetail.strAddress UTF8String], -1,SQLITE_TRANSIENT); sqlite3_bind_text(insertStatement, 4, [objSearchDetail.strEmail UTF8String], -1,SQLITE_TRANSIENT); sqlite3_bind_text(insertStatement, 5, [objSearchDetail.strUrl UTF8String], -1,SQLITE_TRANSIENT); sqlite3_bind_text(insertStatement, 6, [objSearchDetail.strStreet UTF8String], -1,SQLITE_TRANSIENT); sqlite3_bind_text(insertStatement, 7, [objSearchDetail.strPostCode UTF8String], -1,SQLITE_TRANSIENT); sqlite3_bind_text(insertStatement, 8, [objSearchDetail.strPlace UTF8String], -1,SQLITE_TRANSIENT); sqlite3_bind_text(insertStatement, 9, [objSearchDetail.strTelephone UTF8String], -1,SQLITE_TRANSIENT); sqlite3_bind_text(insertStatement, 10, [objSearchDetail.strMobile UTF8String], -1,SQLITE_TRANSIENT); if(sqlite3_step(insertStatement)==SQLITE_DONE) { //Data; } } NSLog(@"count %d",[objSearchDetail retainCount]); [objSearchDetail release]; now the nslog shows refrence count as 2 so even if i release the refrence count will still be one and the object will not be destroyed.. plz help me....

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• What is a recommended Android utility class collection?

  - by Sebastian Roth

  I often find myself writing very similar code across projects. And more often than not, I copy stuff over from old projects. Things like: Create images with round corners read density into a static variable & re-use. 4 lines.. disable / hide multiple views / remote views at once. Example: } public static void disableViews(RemoteViews views, int... ids) { for (int id : ids) { views.setInt(id, SET_VISIBILITY, View.GONE); } } public static void showViews(RemoteViews views, int... ids) { for (int id : ids) { views.setInt(id, SET_VISIBILITY, View.VISIBLE); } } I'd love to package these kind of functions into 1 letter / 2 letter class names, i.e. V.showViews(RemoteViews views, int... ids) would be easy to write & remember I hope. I'm searching for Github recommendations, links and if nothing is found, I perhaps will start a small project on github to collect.

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• Perl TCP Server handling multiple Client connections

  - by Matt

  I'll preface this by saying I have minimal experience with both Perl and Socket programming, so I appreciate any help I can get. I have a TCP Server which needs to handle multiple Client connections simultaneously and be able to receive data from any one of the Clients at any time and also be able to send data back to the Clients based on information it's received. For example, Client1 and Client2 connect to my Server. Client2 sends "Ready", the server interprets that and sends "Go" to Client1. The following is what I have written so far: my $sock = new IO::Socket::INET { LocalHost => $host, // defined earlier in code LocalPort => $port, // defined earlier in code Proto => 'tcp', Listen => SOMAXCONN, Reuse => 1, }; die "Could not create socket $!\n" unless $sock; while ( my ($new_sock,$c_addr) = $sock->accept() ) { my ($client_port, $c_ip) = sockaddr_in($c_addr); my $client_ipnum = inet_ntoa($c_ip); my $client_host = ""; my @threads; print "got a connection from $client_host", "[$client_ipnum]\n"; my $command; my $data; while ($data = <$new_sock>) { push @threads, async \&Execute, $data; } } sub Execute { my ($command) = @_; // if($command) = "test" { // send "go" to socket1 print "Executing command: $command\n"; system($command); } I know both of my while loops will be blocking and I need a way to implement my accept command as a thread, but I'm not sure the proper way of writing it.

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• Optimize SQL connection?

  - by user1484035

  I am building a multi-page web project in HTML and Javascript that is constantly reading from AND writing to an SQL database. I can connect to the database and successfully run my project with this type of connection. var connection = new ActiveXObject("ADODB.Connection") ; var connectionstring="Data Source=<server>;Initial Catalog=<catalog>;User ID=<user>; Password=<password>;Provider=SQLOLEDB"; connection.Open(connectionstring); var rs = new ActiveXObject("ADODB.Recordset"); rs.Open("SELECT * FROM table", connection); rs.MoveFirst while(!rs.eof) { document.write(rs.fields(1)); rs.movenext; } rs.close; connection.close; Works great and runs fine. BUT, the first 5 lines (from var connection = to var rs =) causes the whole browser to freeze for a few seconds while it establishes the connection. I need to speed that up since I am constantly connecting to the database throughout my project. Is there a more effective way of connecting to a SQL database? or is my computer just bad and this should run faster?

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• password-check directive in angularjs

  - by mpm

  I'm writing a password verify directive : Directives.directive("passwordVerify",function(){ return { require:"ngModel", link: function(scope,element,attrs,ctrl){ ctrl.$parsers.unshift(function(viewValue){ var origin = scope.$eval(attrs["passwordVerify"]); if(origin!==viewValue){ ctrl.$setValidity("passwordVerify",false); return undefined; }else{ ctrl.$setValidity("passwordVerify",true); return viewValue; } }); } }; }); html : <input data-ng-model='user.password' type="password" name='password' placeholder='password' required> <input data-ng-model='user.password_verify' type="password" name='confirm_password' placeholder='confirm password' required data-password-verify="user.password"> Given 2 password fields in a form, if both password values are equal then the field affected by the directive is valid. The issue is that it works one way (i.e. when I type a password in the password-verify field). However, when the original password field is updated, the password-verify doesn't become valid. Any idea how I could have a "two way binding verify?"

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• Google Drive API invalid_grant after removing access

  - by Sparafusile

  I have been writing a desktop application that uses the Google Drive API v2. I have the following code: var credential = GoogleWebAuthorizationBroker.AuthorizeAsync ( new ClientSecrets { ClientId = ClientID, ClientSecret = ClientSecret }, new[] { DriveService.Scope.Drive }, "user", CancellationToken.None ) .Result; this.Service = new DriveService( new BaseClientService.Initializer() { HttpClientInitializer = credential, ApplicationName = "My Test App", } ); var request = this.Service.Files.List(); request.Q = "title = 'foo' and trashed = false"; var result = request.Execute(); The first time I ran this code it opened a browser and asked me to grant permissions to the App, which I did. Everything worked successfully until I realized I was using the wrong Google account. At that point I logged into the wrong Google account and revoked access to my App. Now, whenever I run the same code it throws an exception: Error:"invalid_grant", Description:"", Uri:"" When I examine the service and request objects, it looks like the oauth_token isn't getting created any more. I know what I did to mess things up, but I can't figure out how to correct it so I can use a different Google account for testing. What do I need to do?

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• Reason for socket.error

  - by August Flanagan

  Hi, I am a complete newbie when it comes to python, and programming in general. I've been working on a little webapp for the past few weeks trying to improve my coding chops. A few days ago my laptop was stolen so I went out and got a new MacBook Pro. Thank God I had everything under subversion control. The problem is now that I am on my new machine a script that I was running has stopped working and I have no idea why. This is really the only part of what I have been writing that I borrowed heavily for existing scripts. It is from the widely available whois.py script and I have only slightly modified it as follows (see below). It was running fine on my old system (running ubuntu), but now the socket.error is being raised. I'm completely lost on this, and would really appreciate any help. Thanks! def is_available(domainname, whoisserver="whois.verisign-grs.com", cache=0): if whoisserver is None: whoisserver = "whois.networksolutions.com" s = None while s == None: try: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.setblocking(0) try: s.connect((whoisserver, 43)) except socket.error, (ecode, reason): if ecode in (115, 150): pass else: raise socket.error, (ecode, reason) ret = select.select([s], [s], [], 30) if len(ret[1])== 0 and len(ret[0]) == 0: s.close() raise TimedOut, "on connect " s.setblocking(1) except socket.error, (ecode, reason): print ecode, reason time.sleep(1) s = None s.send("%s \n\n" % domainname) page = "" while 1: data = s.recv(8196) if not data: break page = page + data s.close()

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• How can I make VS2010 insert using statements in the order dictated by StyleCop rules.

  - by Hamish Grubijan

  The related default StyleCop rules are: Place using statements inside namespace. Sort using statements alphabetically. But ... System using come first (still trying to figure out if that means just using System; or using System[.*];). So, my use case: I find a bug and decide that I need to at least add an intelligible Assert to make debugging less painful for the next guy. So I start typing Debug.Assert( and intellisense marks it in Red. I hover mouse over Debug and between using System.Diagnostics; and System.Diagnostics.Debug I choose the former. This inserts using System.Diagnostics; after all other using statements. It would be nice if VS2010 did not assist me in writing code that won't build due to warnings as errors. How can I make VS2010 smarter? Is there some sort of setting, or does this require a full-fledged add-in of some sort?

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• Why the compiler is not compiling a line in C++ Builder?

  - by MLB

  Hi boys: I was programming an application in C++ Builder 6, and I had encountered this rare problem: void RotateDice() { Graphics::TBitmap *MYbitmap = new Graphics::TBitmap(); Randomize(); int rn = random(6) + 1; switch (rn) { case 1: { //... break; } //... Some cases... } ShowDice(); //it's a function to show the dice delete MYbitmap; //the compiler don't get it!!!! } In the line "ShowDice()", the compiler jumps to the final of the RotateDice() method, it doesn't "see" the line "delete MYbitmap". When I compile the program, every compiled line shows a little blue point in its left side, but that line don't show the blue point... it's like the compiler don't "see" the line of code. What's happening with that???? Note: Some days ago, I was writing a program in Delphi and I was advice of that problematic issue. Some like that happened to me in Delphi 7... So, waht the problem with that? I am so sorry about my English. I am from Cuba.

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• Inheritance of TCollectionItem

  - by JamesB

  I'm planning to have collection of items stored in a TCollection. Each item will derive from TBaseItem which in turn derives from TCollectionItem, With this in mind the Collection will return TBaseItem when an item is requested. Now each TBaseItem will have a Calculate function, in the the TBaseItem this will just return an internal variable, but in each of the derivations of TBaseItem the Calculate function requires a different set of parameters. The Collection will have a Calculate All function which iterates through the collection items and calls each Calculate function, obviously it would need to pass the correct parameters to each function I can think of three ways of doing this: Create a virtual/abstract method for each calculate function in the base class and override it in the derrived class, This would mean no type casting was required when using the object but it would also mean I have to create lots of virtual methods and have a large if...else statement detecting the type and calling the correct "calculate" method, it also means that calling the calculate method is prone to error as you would have to know when writing the code which one to call for which type with the correct parameters to avoid an Error/EAbstractError. Create a record structure with all the possible parameters in and use this as the parameter for the "calculate" function. This has the added benefit of passing this to the "calculate all" function as it can contain all the parameters required and avoid a potentially very long parameter list. Just type casting the TBaseItem to access the correct calculate method. This would tidy up the TBaseItem quite alot compared to the first method. What would be the best way to handle this collection?

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• What is the purpose of the QAbstractButton::checkStateSet() method?

  - by darkadept

  I'm writing my own 4 state button and I'm not quite sure what to put in the checkStateSet() method, if anything. Here is what I've got so far: SyncDirectionButton::SyncDirectionButton(QWidget *parent) : QAbstractButton(parent) { setCheckable(true); setToolTip(tr("Click to change the sync direction")); _state = NoSync; } void SyncDirectionButton::paintEvent(QPaintEvent *e) { static QPixmapCache::Key noneKey; static QPixmapCache::Key bothKey; static QPixmapCache::Key leftKey; static QPixmapCache::Key rightKey; QPainter p(this); QPixmap pix; if (checkState() == SyncLeft) { if (!QPixmapCache::find(leftKey, &pix)) { pix.load(":/icons/sync-left.png"); leftKey = QPixmapCache::insert(pix); } } else if (checkState() == SyncBoth) { if (!QPixmapCache::find(rightKey, &pix)) { pix.load(":/icons/sync-right.png"); rightKey = QPixmapCache::insert(pix); } } else if (checkState() == SyncRight) { if (!QPixmapCache::find(bothKey, &pix)) { pix.load(":/icons/sync-both.png"); bothKey = QPixmapCache::insert(pix); } } else if (checkState() == NoSync) { if (!QPixmapCache::find(noneKey, &pix)) { pix.load(":/icons/application-exit.png"); noneKey = QPixmapCache::insert(pix); } } p.drawPixmap(0,0,pix); } SyncDirectionButton::DirectionState SyncDirectionButton::checkState() const { return _state; } void SyncDirectionButton::setCheckState(DirectionState state) { setChecked(state != NoSync); if (state != _state) { _state = state; } } QSize SyncDirectionButton::sizeHint() const { return QSize(180,90); } void SyncDirectionButton::checkStateSet() { } void SyncDirectionButton::nextCheckState() { setCheckState((DirectionState)((checkState()+1)%4)); }

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• JSP includes and MVC pattern

  - by xingyu

  I am new to JSP/Servlets/MVC and am writing a JSP page (using Servlets and MVC pattern) that displays information about recipies, and want the ability for users to "comment" on it too. So for the Servlet, on doGet(), it grabs all the required info into a Model POJO and forwards the request on to a JSP View for rendering. That is working just fine. I'd like the "comment" part to be a separate JSP, so on the RecipeView.jsp I can use to separate these views out. So I've made that, but am now a little stuck. The form in the CommentOnRecipe.jsp posts to a CommentAction servlet that handles the recording of the comment just fine. So when I reload the Recipe page, I can see the comment I just made. I'd like to: Reload the page automatically after commenting (no AJAX for now) Block the user from making more than one comment on each Recipe over a 1 day timeframe (via a Cookie). So I store a cookie indicating the product ID whenever the user makes a comment, so we can check this later? How would it work in a MVC context? Show a message to the user that they have already commented on the Recipe when they visit one which they have commented on I'm confused about using beans/including JSPs etc on how to achieve this. I know in ASP.NET land, it would be a UseControl that I would place on a page, or in ASP.NET MVC, it would be a PartialView of some sort. I'm just confused with the way this works in a JSP/Servlets/MVC context.

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• AttributeError in my Python program regarding classes

  - by Axel Finkel

  I'm doing an exercise out of the Python book that involves creating a class and a subclass. I am getting the following error when I try to run the program: AttributeError: 'Customer' object has no attribute 'name', when it tries to go through this bit of code: self.name.append(name) As this is my first time dealing with classes and objects in Python, I'm sure I am making some overt mistake somewhere, but I can't seem to figure it out. I've looked over the documentation for creating classes and writing member functions, and it looks correct, but it is obviously not. I want the Customer subclass to inherit the name, address, and telephone attributes from the Person superclass, but it doesn't seem to be doing so? Here is my code: class Person: def __init__(self): self.name = None self.address = None self.telephone = None def changeName(self, name): self.name.append(name) def changeAddress(self, address): self.address.append(address) def changeTelephone(self, telephone): self.telephone.append(telephone) class Customer(Person): def __init__(self): self.customerNumber = None self.onMailingList = False def changeCustomerNumber(self, customerNumber): self.customerNumber.append(customerNumber) def changeOnMailingList(): if onMailingList == False: onMailingList == True else: onMailingList == False def main(): customer1 = Customer() name = 'Bob Smith' address = '123 Somewhere Road' telephone = '111 222 3333' customerNumber = '12345' customer1.changeName(name) customer1.changeAddress(address) customer1.changeTelephone(telephone) customer1.changeCustomerNumber(customerNumber) print("Customer name: " + customer1.name) print("Customer address: " + customer1.address) print("Customer telephone number: " + customer1.telephone) print("Customer number: " + customer1.customerNumber) print("On mailing list: " + customer1.OnMailingList) customer1.changeOnMailingList() print("On mailing list: " + customer1.OnMailingList) main()

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• GADTs and Scrap your Boilerplate

  - by finnsson

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

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• Freeing ImageData when deleting a Canvas

  - by user578770

  I'm writing a XUL application using HTML Canvas to display Bitmap images. I'm generating ImageDatas and imporingt them in a canvas using the putImageData function : for(var pageIndex=0;pageIndex<100;pageIndex++){ this.img = imageDatas[pageIndex]; /* Create the Canvas element */ var imgCanvasTmp = document.createElementNS("http://www.w3.org/1999/xhtml",'html:canvas'); imgCanvasTmp.setAttribute('width', this.img.width); imgCanvasTmp.setAttribute('height', this.img.height); /* Import the image into the Canvas */ imgCanvasTmp.getContext('2d').putImageData(this.img, 0, 0); /* Use the Canvas into another part of the program (Commented out for testing) */ // this.displayCanvas(imgCanvasTmp,pageIndex); } The images are well imported but there seems to be a memory leak due to the putImageData function. When exiting the "for" loop, I would expect the memory allocated for the Canvas to be freed but, by executing the code without executing putImageData, I noticed that my program at the end use 100Mb less (my images are quite big). I came to the conclusion that the putImageData function prevent the garbage collector to free the allocated memory. Do you have any idea how I could force the garbage collector to free the memory? Is there any way to empty the Canvas? I already tried to delete the canvas using the delete operator or to use the clearRect function but it did nothing. I also tried to reuse the same canvas to display the image at each iteration but the amount of memory used did not changed, as if the image where imported without deleting the existing ones...

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• Cost of logic in a query

  - by FrustratedWithFormsDesigner

  I have a query that looks something like this: select xmlelement("rootNode", (case when XH.ID is not null then xmlelement("xhID", XH.ID) else xmlelement("xhID", xmlattributes('true' AS "xsi:nil"), XH.ID) end), (case when XH.SER_NUM is not null then xmlelement("serialNumber", XH.SER_NUM) else xmlelement("serialNumber", xmlattributes('true' AS "xsi:nil"), XH.SER_NUM) end), /*repeat this pattern for many more columns from the same table...*/ FROM XH WHERE XH.ID = 'SOMETHINGOROTHER' It's ugly and I don't like it, and it is also the slowest executing query (there are others of similar form, but much smaller and they aren't causing any major problems - yet). Maintenance is relatively easy as this is mostly a generated query, but my concern now is for performance. I am wondering how much of an overhead there is for all of these case expressions. To see if there was any difference, I wrote another version of this query as: select xmlelement("rootNode", xmlforest(XH.ID, XH.SER_NUM,... (I know that this query does not produce exactly the same, thing, my plan was to move the logic to PL/SQL or XSL) I tried to get execution plans for both versions, but they are the same. I'm guessing that the logic does not get factored into the execution plan. My gut tells me the second version should execute faster, but I'd like some way to prove that (other than writing a PL/SQL test function with timing statements before and after the query and running that code over and over again to get a test sample). Is it possible to get a good idea of how much the case-when will cost? Also, I could write the case-when using the decode function instead. Would that perform better (than case-statements)?

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• How can I use TDD to solve a puzzle with an unknown answer?

  - by matthewsteele

  Recently I wrote a Ruby program to determine solutions to a "Scramble Squares" tile puzzle: I used TDD to implement most of it, leading to tests that looked like this: it "has top, bottom, left, right" do c = Cards.new card = c.cards[0] card.top.should == :CT card.bottom.should == :WB card.left.should == :MT card.right.should == :BT end This worked well for the lower-level "helper" methods: identifying the "sides" of a tile, determining if a tile can be validly placed in the grid, etc. But I ran into a problem when coding the actual algorithm to solve the puzzle. Since I didn't know valid possible solutions to the problem, I didn't know how to write a test first. I ended up writing a pretty ugly, untested, algorithm to solve it: def play_game working_states = [] after_1 = step_1 i = 0 after_1.each do |state_1| step_2(state_1).each do |state_2| step_3(state_2).each do |state_3| step_4(state_3).each do |state_4| step_5(state_4).each do |state_5| step_6(state_5).each do |state_6| step_7(state_6).each do |state_7| step_8(state_7).each do |state_8| step_9(state_8).each do |state_9| working_states << state_9[0] end end end end end end end end end So my question is: how do you use TDD to write a method when you don't already know the valid outputs? If you're interested, the code's on GitHub: Tests: https://github.com/mattdsteele/scramblesquares-solver/blob/master/golf-creator-spec.rb Production code: https://github.com/mattdsteele/scramblesquares-solver/blob/master/game.rb

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• Emulating a computer running MS-DOS

  - by Richard

  Writing emulators has always fascinated me. Now I want to write an emulator for an IBM PC and run MS-DOS on it (I've got the floppy image files). I have good experience in C++ and C and basic knowledge of assembler and the architecture of a CPU. I also know that there are thousands of emulators out there doing exactly what I want to do, but I'd be doing this for pure joy only. How much work do I have to expect? (If my goal is to boot DOS and create a text file with it, all emulated) What CPU should I emulate ? Where can I find documentation on how the machine code is organized and which opcodes mean what, so I can unpack and execute them correctly with my emulator? Does MS-DOS still run on the newest generations of processors? Would it theoretically be able to natively run on a 64-bit AMD Phenom 2 processor w/ a modern mainboard, HDD, RAM, etc.? What else, besides emulating the CPU, could be an important factor (in terms of difficulty)? I would only aim for outputting / inputting text to the system via the host system's console, no sound or other more advanced IO etc. Have you written an emulator yet? What was your first one for? How hard was it? Do you have any special tips for me? Thanks in advance

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