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• How to define a "complicated" ComputedColumn in SQL Server?

  - by Slauma

  SQL Server Beginner question: I'm trying to introduce a computed column in SQL Server (2008). In the table designer of SQL Server Management Studio I can do this, but the designer only offers me one single edit cell to define the expression for this column. Since my computed column will be rather complicated (depending on several database fields and with some case differentiations) I'd like to have a more comfortable and maintainable way to enter the column definition (including line breaks for formatting and so on). I've seen there is an option to define functions in SQL Server (scalar value or table value functions). Is it perhaps better to define such a function and use this function as the column specification? And what kind of function (scalar value, table value)? To make a simplified example: I have two database columns: DateTime1 (smalldatetime, NULL) DateTime2 (smalldatetime, NULL) Now I want to define a computed column "Status" which can have four possible values. In Dummy language: if (DateTime1 IS NULL and DateTime2 IS NULL) set Status = 0 else if (DateTime1 IS NULL and DateTime2 IS NOT NULL) set Status = 1 else if (DateTime1 IS NOT NULL and DateTime2 IS NULL) set Status = 2 else set Status = 3 Ideally I would like to have a function GetStatus() which can access the different column values of the table row which I want to compute the value of "Status" for, and then only define the computed column specification as GetStatus() without parameters. Is that possible at all? Or what is the best way to work with "complicated" computed column definitions? Thank you for tips in advance!

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• Django sitemap intermittent www

  - by Jen Z

  The automatic sitemap for my Django site fluctuates between including the www on urls and leaving it out (I'm aiming to have it in all the time). This has ramifications in google not indexing my pages properly so I'm trying to narrow down what would be causing this issue. I have set PREPEND_WWW = True and my site record in the sites framework is set to include the www e.g. it's set to www.example.com as opposed to example.com. I'm using memcached but pages should expire from the cache after 48 hours so I wouldn't have thought that would be causing the issue? You can see the problem in effect at http://www.livingspaceltd.co.uk/sitemap.xml (refresh the page a few times). My sitemaps setup is fairly prosaic so I'm doubtful that that is the issue, but in case it's something obvious I'm missing here's the code: ***urls.py*** sitemaps = { 'subpages': Subpages_Sitemap, 'standalone_pages': Standalone_Sitemap, 'categories': Categories_Sitemap, } urlpatterns = patterns('', (r'^sitemap\.xml$', 'django.contrib.sitemaps.views.sitemap', {'sitemaps': sitemaps}), ... ***sitemaps.py*** # -*- coding: utf-8 -*- from django_ls.livingspace.models import Page, Category, Standalone_Page, Subpage from django.contrib.sitemaps import Sitemap class Subpages_Sitemap(Sitemap): changefreq = "monthly" priority = 0.4 def items(self): return Subpage.objects.filter(restricted_to__isnull=True) class Standalone_Sitemap(Sitemap): changefreq = "weekly" priority = 1 def items(self): return Standalone_Page.objects.all() class Categories_Sitemap(Sitemap): changefreq = "weekly" priority = 0.7 def items(self): return Category.objects.all()

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• How do you make a static sprite be a child of another sprite in cocos2D while using SpaceManager

  - by JJBigThoughts

  I have two static (STATIC_MASS) SpaceManager sprites. One is a child of the other - by which I mean that one sort of builds up the other one, but although the child's images shows up in the right place, the child doesn't seem to exists in the chipmunk physics engine, like I would expect. In my case, I have a backboard (rectangular sprite) and a hoop (a circular sprite). Since I might want to move the backboard, I'd like to attach the hoop to backboard so that the hoop automatically moves right along with the backboard. Here, we see a rotating backboard with attached hoop. It looks OK on the screen, but other objects only bounce off the backboard but pass right through the hoop (in a bad sense of the term). What doesn't my child sprite seem to exist in the physics engine? // Add Backboard cpShape *shapeRect = [smgr addRectAt:cpvWinCenter mass:STATIC_MASS width:200 height:10 rotation:0.0f ];// We're upgrading this cpCCSprite * cccrsRect = [cpCCSprite spriteWithShape:shapeRect file:@"rect_200x10.png"]; [self addChild:cccrsRect]; // Spin the static backboard: http://stackoverflow.com/questions/2691589/how-do-you-make-a-sprite-rotate-in-cocos2d-while-using-spacemanager // Make static object update moves in chipmunk // Since Backboard is static, and since we're going to move it, it needs to know about spacemanager so its position gets updated inside chipmunk. // Setting this would make the smgr recalculate all static shapes positions every step // cccrsRect.integrationDt = smgr.constantDt; // cccrsRect.spaceManager = smgr; // Alternative method: smgr.rehashStaticEveryStep = YES; smgr.rehashStaticEveryStep = YES; // Spin the backboard [cccrsRect runAction:[CCRepeatForever actionWithAction: [CCSequence actions: [CCRotateTo actionWithDuration:2 angle:180], [CCRotateTo actionWithDuration:2 angle:360], nil] ]]; // Add the hoop cpShape *shapeHoop = [smgr addCircleAt:ccp(100,-45) mass:STATIC_MASS radius: 50 ]; cpCCSprite * cccrsHoop = [cpCCSprite spriteWithShape:shapeHoop file:@"hoop_100x100.png"]; [cccrsRect addChild:cccrsHoop]; This is only half working for me. Note: SpaceManager is a toolkit for working with cocos2D-iphone

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• Retrieve a TextBox element dinamically created and Focus it

  - by user335444

  Hi, I have a collection (VariableValueCollection) of custom type VariableValueViewModel objects binded with a ListView. WPF Follow: <ListView ItemsSource="{Binding VariableValueCollection}" Name="itemList"> <ListView.Resources> <DataTemplate DataType="{x:Type vm:VariableValueViewModel}"> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="180"></ColumnDefinition> </Grid.ColumnDefinitions> <TextBox TabIndex="{Binding Path=Index, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" Grid.Column="0" Name="tbValue" Focusable="True" LostFocus="tbValue_LostFocus" GotFocus="tbValue_GotFocus" KeyDown="tbValue_KeyDown"> <TextBox.Text> <Binding Path="Value" UpdateSourceTrigger="PropertyChanged" Mode="TwoWay"> <Binding.ValidationRules> <ExceptionValidationRule></ExceptionValidationRule> </Binding.ValidationRules> </Binding> </TextBox.Text> </TextBox> </Grid> </DataTemplate> </ListView.Resources> </ListView> My Goal is to add a new row when I press "enter" on last row, and Focus the new row. To do that, I check that row is the last row and add a new row in that case. But I don't know how to focus the new TextBox... Here the KeyPressed method: private void tbValue_KeyDown(object sender, KeyEventArgs e) { if (e.Key == System.Windows.Input.Key.Enter) { DependencyObject obj = itemList.ContainerFromElement((sender as TextBox)); int index = itemList.ItemContainerGenerator.IndexFromContainer(obj); if( index == (VariableValueCollection.Count - 1) ) { // Create a VariableValueViewModel object and add to collection. In binding, that create a new list item with a new TextBox ViewModel.AddNewRow(); // How to set cursor and focus last row created? } } } Thank's in advance...

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• Are finalizers ever allowed to call other managed classes' methods?

  - by romkyns

  I used to be pretty sure the answer is "no", as explained in Overriding the Finalize method and Object.Finalize documentation. However, while randomly browsing through FileStream in Reflector, I found that it can actually call just such a method from a finalizer: private SafeFileHandle _handle; ~FileStream() { if (this._handle != null) { this.Dispose(false); } } protected override void Dispose(bool disposing) { try { ... } finally { if ((this._handle != null) && !this._handle.IsClosed) // <=== HERE { this._handle.Dispose(); // <=== AND HERE } [...] } } I started wondering whether this will always work due to the exact way in which it's written, and hence whether the "do not touch managed classes from finalizers" is just a guideline that can be broken given a good reason and the necessary knowledge to do it right. I dug a bit deeper and found out that the worst that can happen when the "rule" is broken is that the managed object being accessed had already been finalized, or may be getting finalized in parallel on a separate thread. So if the SafeFileHandle's finalizer didn't do anything that would cause a subsequent call to Dispose fail then the above should be fine... right? Question: so there might after all be situations in which a method on another managed class may be called reliably from a finalizer? I've always believed this to be false, but this code suggests that it's possible and that there can be good enough reasons to do it. Bonus: Observe that the SafeFileHandle will not even know it's being called from a finalizer, since this is just a normal call to Dispose(). The base class, SafeHandle, actually has two private methods, InternalDispose and InternalFinalize, and in this case InternalDispose will be called. Isn't this a problem? Why not?...

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• With NHibernate and Transaction do I rollback on commit failure or does it auto rollback on single c

  - by mattcodes

  I've built the following Dispose method for my Unit Of Work which essentially wraps the active NH session & transaction (transaction set as variable after opening session as to not be replaced if NH session gets new transaction after error) public void Dispose() { Func<ITransaction,bool> transactionStateOkayFunc = trans => trans != null && trans.IsActive && !trans.WasRolledBack; try { if(transactionStateOkayFunc(this.transaction)) { if (HasErrored) { transaction.Rollback(); } else { try { transaction.Commit(); } catch (Exception) { if(transactionStateOkayFunc(transaction)) transaction.Rollback(); throw; } } } } finally { if(transaction != null) transaction.Dispose(); if(session.IsOpen) session.Close(); } I can't help feeling that code is a little bloated, will a transaction automatically rollback is a discrete Commit fails in the case of non-nested transactions? Will Commit or Rollback automatically Dipose the transaction? If not will Session.Close() automatically dispose the associated transaction?

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• IE event callback object JavaScript

  - by Randy Hall

  I may be WAY off on my terminology, so please feel free to correct me. Perhaps this is why I cannot seem to find anything relevant. No libraries, please. I have an event handler, which invokes a callback function. Fancy, right? In IE<9 the this object in the handler is the window. I don't know why, or how to access the correct object. if (document.addEventListener){ element.addEventListener(event, callback, false); } else { element.attachEvent('on' +event, callback); } This part DOES WORK. This part doesn't: function callback(event){ console.log(this); } this in IE is returning [object Window], whereas it returns the element that called the callback function in every other browser. This is cut down significantly from my full script, but this should be everything that's relevant. EDIT This link provided by @metadings How to reference the caller object ("this") using attachEvent is very close. However, there are still two issues. 1) I need to get both the event object and the DOM element calling this function. 2) This event is handled delegation style: there may be child DOM elements firing the event, meaning event.target is not necessarily (and in my case, not typically) the element with the listener.

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• Partially constructed object / Multi threading

  - by reto

  Heya! I'm using joda due to it's good reputation regarding multi threading. It goes great distances to make multi threaded date handling efficient, for example by making all Date/Time/DateTime objects immutable. But here's a situation where I'm not sure if Joda is really doing the right thing. It probably is correct, but I'd be very interested to see the explanation for it. When a toString() of a DateTime is being called Joda does the following: /* org.joda.time.base.AbstractInstant */ public String toString() { return ISODateTimeFormat.dateTime().print(this); } All formatters are thread safe, as they are as well ready-only. But what's about the formatter-factory: private static DateTimeFormatter dt; /* org.joda.time.format.ISODateTimeFormat */ public static DateTimeFormatter dateTime() { if (dt == null) { dt = new DateTimeFormatterBuilder() .append(date()) .append(tTime()) .toFormatter(); } return dt; } This is a common pattern in single threaded applications. I see the following dangers: Race condition during null check -- worst case: two objects get created. No Problem, as this is solely a helper object (unlike a normal singleton pattern situation), one gets saved in dt, the other is lost and will be garbage collected sooner or later. the static variable might point to a partially constructed object before the objec has been finished initialization (before calling me crazy, read about a similar situation in this Wikipedia article. So how does Joda ensure that not partially created formatter gets published in this static variable? Thanks for your explanations! Reto

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• My android tests don't get internet access!

  - by Malachii

  The subject says it all. My application gets internet access thanks to the android.permission.INTERNET permission, but my test cases don't while using the instrumentation test runner. This means I can't test my server IO routines in my test cases. What's up? Here's my manifest in case it helps you. Thanks! Sorry about the lack of indents - could not get it working on short notice with this site. Thanks! <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.helloandroid" android:versionCode="1" android:versionName="1.0"> <uses-permission android:name="android.permission.INTERNET"></uses-permission> <application android:icon="@drawable/icon" android:label="@string/app_name"> <uses-library android:name="android.test.runner" /> <activity android:name=".HelloAndroid" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> <uses-sdk android:minSdkVersion="2" /> <instrumentation android:name="android.test.InstrumentationTestRunner" android:targetPackage="qnext.mobile.redirect" android:label="Qnext Redirect Tests" /> </manifest>

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• Is there a language with native pass-by-reference/pass-by-name semantics, which could be used in mod

  - by Bubba88

  Hi! This is a reopened question. I look for a language and supporting platform for it, where the language could have pass-by-reference or pass-by-name semantics by default. I know the history a little, that there were Algol, Fortran and there still is C++ which could make it possible; but, basically, what I look for is something more modern and where the mentioned value pass methodology is preferred and by default (implicitly assumed). I ask this question, because, to my mind, some of the advantages of pass-by-ref/name seem kind of obvious. For example when it is used in a standalone agent, where copyiong of values is not necessary (to some extent) and performance wouldn't be downgraded much in that case. So, I could employ it in e.g. rich client app or some game-style or standalone service-kind application. The main advantage to me is the clear separation between identity of a symbol, and its current value. I mean when there is no reduntant copying, you know that you're working with the exact symbol/path you have queried/received. And intristing boxing of values will not interfere with the actual logic of program. I know that there is C# ref keyword, but it's something not so intristic, though acceptable. Equally, I realize that pass-by-reference semantics could be simulated in virtually any language (Java as an instant example) and so on.. not sure about pass by name :) What would you recommend - create a something like DSL for such needs wherever it be appropriate; or use some languages that I already know? Maybe, there is something that I'm missing? Thank you!

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• Wait on multiple condition variables on Linux without unnecessary sleeps?

  - by Joseph Garvin

  I'm writing a latency sensitive app that in effect wants to wait on multiple condition variables at once. I've read before of several ways to get this functionality on Linux (apparently this is builtin on Windows), but none of them seem suitable for my app. The methods I know of are: Have one thread wait on each of the condition variables you want to wait on, which when woken will signal a single condition variable which you wait on instead. Cycling through multiple condition variables with a timed wait. Writing dummy bytes to files or pipes instead, and polling on those. #1 & #2 are unsuitable because they cause unnecessary sleeping. With #1, you have to wait for the dummy thread to wake up, then signal the real thread, then for the real thread to wake up, instead of the real thread just waking up to begin with -- the extra scheduler quantum spent on this actually matters for my app, and I'd prefer not to have to use a full fledged RTOS. #2 is even worse, you potentially spend N * timeout time asleep, or your timeout will be 0 in which case you never sleep (endlessly burning CPU and starving other threads is also bad). For #3, pipes are problematic because if the thread being 'signaled' is busy or even crashes (I'm in fact dealing with separate process rather than threads -- the mutexes and conditions would be stored in shared memory), then the writing thread will be stuck because the pipe's buffer will be full, as will any other clients. Files are problematic because you'd be growing it endlessly the longer the app ran. Is there a better way to do this? Curious for answers appropriate for Solaris as well.

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• inserting a form to session raises picklingerror - django

  - by shanyu

  I receive an exception when I add a form to the session: PicklingError: Can't pickle <class 'django.utils.functional.__proxy__'>: attribute lookup django.utils.functional.__proxy__ failed The form includes a few simple fields and has some javascript attached to a widget. It might be that Django forms cannot be pickled at all, but the exception seems to point to unicode lazy translation. To test further, I have also tried to insert only the form errors (an errordict) to the session and received the same error. I appreciate some help here, thanks in advance. EDIT: Here's why I insert a form into the session: I have an app that has a form. This form is rendered by a template tag in another app. When posted, if the form is valid, no problem, I do stuff and redirect to "next". However if it is not valid, I want to go back to the posting page to show errors. Recall that the comments app in this case redirects to an intermediate "hey, please fix the errors" page. I am trying to avoid this, and hence redirect back to the posting page with the form and its errors in the session that the template tag will render.

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• BeginInvoke on ObservableCollection not immediate.

  - by Padu Merloti

  In my code I subscribe to an event that happens on a different thread. Every time this event happens, I receive an string that is posted to the observable collection: Dispatcher currentDispatcher = Dispatcher.CurrentDispatcher; var SerialLog = new ObservableCollection<string>(); private void hitStation_RawCommandSent(object sender, StringEventArgs e) { string command = e.Value.Replace("\r\n", ""); Action dispatchAction = () => SerialLog.Add(command); currentDispatcher.BeginInvoke(dispatchAction, DispatcherPriority.Render); } The code below is in my view model (could be in the code behind, it doesn't matter in this case). When I call "hitstation.PrepareHit", the event above gets called a couple times, then I wait and call "hitStation.HitBall", and the event above gets called a couple more times. private void HitBall() { try { try { Mouse.OverrideCursor = Cursors.Wait; //prepare hit hitStation.PrepareHit(hitSpeed); Thread.Wait(1000); PlayWarning(); //hit hitStation.HitBall(hitSpeed); } catch (TimeoutException ex) { MessageBox.Show("Timeout hitting ball: " + ex.Message); } } finally { Mouse.OverrideCursor = null; } } The problem I'm having is that the ListBox that is bound to my SerialLog gets updated only when the HitBall method finishes. I was expecting seeing a bunch of updates from the PrepareHit, a pause and then a bunch more updates from the HitBall. I've tried a couple of DispatcherPriority arguments, but they don't seem to have any effect.

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• ActiveRecord exceptions not rescued

  - by zoopzoop

  I have the following code block: unless User.exist?(...) begin user = User.new(...) # Set more attributes of user user.save! rescue ActiveRecord::RecordInvalid, ActiveRecord::RecordNotUnique => e # Check if that user was created in the meantime user = User.exists?(...) raise e if user.nil? end end The reason is, as you can probably guess, that multiple processes might call this method at the same time to create the user (if it doesn't already exist), so while the first one enters the block and starts initializing a new user, setting the attributes and finally calling save!, the user might already be created. In that case I want to check again if the user exists and only raise the exception if it still doesn't (= if no other process has created it in the meantime). The problem is, that regularly ActiveRecord::RecordInvalid exceptions are raised from the save! and not rescued from the rescue block. Any ideas? EDIT: Alright, this is weird. I must be missing something. I refactored the code according to Simone's tip to look like this: unless User.find_by_email(...).present? # Here we know the user does not exist yet user = User.new(...) # Set more attributes of user unless user.save # User could not be saved for some reason, maybe created by another request? raise StandardError, "Could not create user for order #{self.id}." unless User.exists?(:email => ...) end end Now I got the following exception: ActiveRecord::RecordNotUnique: Mysql::DupEntry: Duplicate entry '[email protected]' for key 'index_users_on_email': INSERT INTO `users` ... thrown in the line where it says 'unless user.save'. How can that be? Rails thinks the user can be created because the email is unique but then the Mysql unique index prevents the insert? How likely is that? And how can it be avoided?

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• How can I superimpose modified loess lines on a ggplot2 qplot?

  - by briandk

  Background Right now, I'm creating a multiple-predictor linear model and generating diagnostic plots to assess regression assumptions. (It's for a multiple regression analysis stats class that I'm loving at the moment :-) My textbook (Cohen, Cohen, West, and Aiken 2003) recommends plotting each predictor against the residuals to make sure that: The residuals don't systematically covary with the predictor The residuals are homoscedastic with respect to each predictor in the model On point (2), my textbook has this to say: Some statistical packages allow the analyst to plot lowess fit lines at the mean of the residuals (0-line), 1 standard deviation above the mean, and 1 standard deviation below the mean of the residuals....In the present case {their example}, the two lines {mean + 1sd and mean - 1sd} remain roughly parallel to the lowess {0} line, consistent with the interpretation that the variance of the residuals does not change as a function of X. (p. 131) How can I modify loess lines? I know how to generate a scatterplot with a "0-line,": # First, I'll make a simple linear model and get its diagnostic stats library(ggplot2) data(cars) mod <- fortify(lm(speed ~ dist, data = cars)) attach(mod) str(mod) # Now I want to make sure the residuals are homoscedastic qplot (x = dist, y = .resid, data = mod) + geom_smooth(se = FALSE) # "se = FALSE" Removes the standard error bands But does anyone know how I can use ggplot2 and qplot to generate plots where the 0-line, "mean + 1sd" AND "mean - 1sd" lines would be superimposed? Is that a weird/complex question to be asking?

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• should the builder reset its build environment after delivering the product

  - by Sudhi

  I am implementing a builder where in the deliverable is retrieved by calling Builder::getProduct() . The director asks various parts to build Builder::buildPartA() , Builder::buildPartB() etc. in order to completely build the product. My question is, once the product is delivered by the Builder by calling Builder::getProduct(), should it reset its environment (Builder::partA = NULL;, Builder::partB = NULL;) so that it is ready to build another product? (with same or different configuration?) I ask this as I am using PHP wherein the objects are by default passed by reference (nope, I don't want to clone them, as one of their field is a Resource) . However, even if you think from a language agnostic point of view, should the Builder reset its build environment ? If your answer is 'it depends on the case' what use cases would justify reseting the environment (and other way round) ? For the sake of providing code sample here's my Builder::gerProcessor() which shows what I mean by reseting the environment /** * @see IBuilder::getProessor() */ public function getProcessor() { if($this->_processor == NULL) { throw new LogicException('Processor not yet built!'); } else { $retval = $this->_processor; $this->_product = NULL, $this->_processor = NULL; } return $retval; }

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• Java enums in generic type

  - by Marcin Cylke

  Hi, I'd like to create a generic enum-based mapper for IBatis. I'm doing this with the below code. This does have compile time errors, which I don't know how to fix. Maybe my solution is just plain wrong (keep in mind the use of IBatis), in such case please suggest something better. Any help appreciated. What I want to achieve is to define subsequent mappers as: public class XEnumTypeHandler extends CommonEnumTypeHandler<X> { } The current code: public class CommonEnumTypeHandler<T extends Enum> implements TypeHandlerCallback { public void setParameter(ParameterSetter ps, Object o) throws SQLException { if (o.getClass().isAssignableFrom(**T**)) { ps.setString(((**T**) o).value().toUpperCase()); } else throw new SQLException("Excpected ParameterType object than: " + o); } public Object getResult(ResultGetter rs) throws SQLException { Object o = valueOf(rs.getString()); if (o == null) throw new SQLException("Unknown parameter type: " + rs.getString()); return o; } public Object valueOf(String s) { for (T pt : T.**values()**) { if (pt.**value()**.equalsIgnoreCase(s)) return pt; } return null; } } I've added error markings to the above code, the error messages are in order: T cannot be resolved The method value() is undefined for the type T The method values() is undefined for the type T The method values() is undefined for the type T

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• How do I join three tables with SQLalchemy and keeping all of the columns in one of the tables?

  - by jimka

  So, I have three tables: The class defenitions: engine = create_engine('sqlite://test.db', echo=False) SQLSession = sessionmaker(bind=engine) Base = declarative_base() class Channel(Base): __tablename__ = 'channel' id = Column(Integer, primary_key = True) title = Column(String) description = Column(String) link = Column(String) pubDate = Column(DateTime) class User(Base): __tablename__ = 'user' id = Column(Integer, primary_key = True) username = Column(String) password = Column(String) sessionId = Column(String) class Subscription(Base): __tablename__ = 'subscription' userId = Column(Integer, ForeignKey('user.id'), primary_key=True) channelId = Column(Integer, ForeignKey('channel.id'), primary_key=True) And the SQL commands that are executed to create them: CREATE TABLE subscription ( "userId" INTEGER NOT NULL, "channelId" INTEGER NOT NULL, PRIMARY KEY ("userId", "channelId"), FOREIGN KEY("userId") REFERENCES user (id), FOREIGN KEY("channelId") REFERENCES channel (id) ); CREATE TABLE user ( id INTEGER NOT NULL, username VARCHAR, password VARCHAR, "sessionId" VARCHAR, PRIMARY KEY (id) ); CREATE TABLE channel ( id INTEGER NOT NULL, title VARCHAR, description VARCHAR, link VARCHAR, "pubDate" TIMESTAMP, PRIMARY KEY (id) ); NOTE: I know user.username should be unique, need to fix that, and I'm not sure why SQLalchemy creates some row names with the double-quotes. And I'm trying to come up with a way to retrieve all of the channels, as well as an indication on what channels one particular user (identified by user.sessionId together with user.id) has a subscription on. For example, say we have four channels: channel1, channel2, channel3, channel4; a user: user1; who has a subscription on channel1 and channel4. The query for user1 would return something like: channel.id | channel.title | subscribed --------------------------------------- 1 channel1 True 2 channel2 False 3 channel3 False 4 channel4 True This is a best-case result, but since I have absolutely no clue as how to accomplish the subscribed column, I've been instead trying to get the particular users id in the rows where the user has a subscription and where a subscription is missing, just leave it blank. The database engine that I'm using together with SQLalchemy atm. is sqlite3 I've been scratching my head over this for two days now, I've no problem joining together all three by way of the subscription table but then all of the channels where the user does not have a subscription gets omitted. I hope I've managed to describe my problem sufficiently, thanks in advance.

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• Is this a variation of the traveling salesman problem?

  - by Ville Koskinen

  I'm interested in a function of two word lists, which would return an order agnostic edit distance between them. That is, the arguments would be two lists of (let's say space delimited) words and return value would be the minimum sum of the edit (or Levenshtein) distances of the words in the lists. Distance between "cat rat bat" and "rat bat cat" would be 0. Distance between "cat rat bat" and "fat had bad" would be the same as distance between "rat bat cat" and "had fat bad", 4. In the case the number of words in the lists are not the same, the shorter list would be padded with 0-length words. My intuition (which hasn't been nurtured with computer science classes) does not find any other solution than to use brute force: |had|fat|bad| a solution ---+---+---+---+ +---+---+---+ cat| 2 | 1 | 2 | | | 1 | | ---+---+---+---+ +---+---+---+ rat| 2 | 1 | 2 | | 3 | | | ---+---+---+---+ +---+---+---+ bat| 2 | 1 | 1 | | | | 4 | ---+---+---+---+ +---+---+---+ Starting from the first row, pick a column and go to the next rows without ever revisiting a column you have already visited. Do this over and over again until you've tried all combinations. To me this sounds a bit like the traveling salesman problem. Is it, and how would you solve my particular problem?

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• Building Paypal based membership website - total noob - would appreciate help

  - by Ali

  this is a follow up on my question on paypal integration. I'm working ona membership site for racing fans. My membership site has 3 membership levels - free, gold and premium. When a user signs up he/she can gets a free membership on the spot but has the option to upgrade to a gold membership for 4 Dollars a month or a premium membership for 10 Dollars a month. I've gone through the paypal integration guide a few times though and have a vague understanding of how to get this to work. I think the recurring payments option would be fine enough - however I don't know how do I implement this in my system. Like when a user decides to go for a paid account i.e. Gold or premium from basic - what should I do on both my code side and on the paypal account side - I'd really appreciate if anyone would outline what I'd have to do here. Plus when a user decides to upgrade from lets say a Gold to a premium account - there is the issue of computing how much should be charged to upgrade his/her account eg: a user has been billed for 4 dollars and the next day opts to go for a premium account so assuming that the surplus for the rest of the month is 5 dollars and further from that all payments would be recurring 10 dollars monthly - how do I implement this? And in case a user decides to downgrade from a premium account of 10 dollars a month to a gold account of 4 dollars a month - how do I handle the surplus which would have to be refunded for that month alone and changing the membership? And like wise if someone wishes to cancel membership and go to having a free account - how do I refund whatever is owed and cancel the subscription. I'm sorry if it sounds like I'm asking to be spoon fed :( I'm quite new to this and this is for a client and I would really appreciate all the help here and really have to get this working right. Thanks again everyone - waiting for all your replies.

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• Testing Broadcasting and receiving messages

  - by Avik

  Guys am having some difficulty figuring this out: I am trying to test whether the code(in c#) to broadcast a message and receiving the message works: The code to send the datagram(in this case its the hostname) is: public partial class Form1 : Form { String hostName; byte[] hostBuffer = new byte[1024]; public Form1() { InitializeComponent(); StartNotification(); } public void StartNotification() { IPEndPoint notifyIP = new IPEndPoint(IPAddress.Broadcast, 6000); hostName = Dns.GetHostName(); hostBuffer = Encoding.ASCII.GetBytes(hostName); UdpClient newUdpClient = new UdpClient(); newUdpClient.Send(hostBuffer, hostBuffer.Length, notifyIP); } } And the code to receive the datagram is: public partial class Form1 : Form { byte[] receivedNotification = new byte[1024]; String notificationReceived; StringBuilder listBox; UdpClient udpServer; IPEndPoint remoteEndPoint; public Form1() { InitializeComponent(); udpServer = new UdpClient(new IPEndPoint(IPAddress.Any, 1234)); remoteEndPoint=null; startUdpListener1(); } public void startUdpListener1() { receivedNotification = udpServer.Receive(ref remoteEndPoint); notificationReceived = Encoding.ASCII.GetString(receivedNotification); listBox = new StringBuilder(this.listBox1.Text); listBox.AppendLine(notificationReceived); this.listBox1.Items.Add(listBox.ToString()); } } For the reception of the code I have a form that has only a listbox(listBox1). The problem here is that when i execute the code to receive, the program runs but the form isnt visible. However when I comment the function call( startUdpListener1() ), the purpose isnt served but the form is visible. Whats going wrong?

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• On-Demand thumbnail creation with django and nginx

  - by sharjeel

  I want to generate thumbnails of images on the fly. My site is built with django and deployed using nginx which serves all the static content and communicates with django/apache using reverse proxy. Right now, for every image in my site, I generate all required sizes of thumbnails on-hand and deliver them when required. The problem is that whenever I change the size of a thumbnail, I have to regenerate all of them (and they are tons). However now I'd like to generate the thumbnail the first time it is accessed and later on nginx would deliver the same file over n over. If I delete that thumbnail file because of lesser accesses, it should get generated automatically the next time. Thumbnails in my case also have watermarks which require some computation logic of my application so a webserver thumbnail module might not work very well. The size of the thumbnail can be embedded in the URL. So http://www.example.com/thumbnail/abc_320x240.jpg gets the 320x240 size of the thumbnail. The approach I'm looking right now is to let nginx lookup the file and if it doesn't exist, forward the query to my django application which would create the thumbnail and send either the response or a redirect string. However I'm not sure about the concurrency issues and any other issues which might pop up later. What is the appropriate way to achieve this?

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• Testing for interface implementation in WCF/SOA

  - by rabidpebble

  I have a reporting service that implements a number of reports. Each report requires certain parameters. Groups of logically related parameters are placed in an interface, which the report then implements: [ServiceContract] [ServiceKnownType(typeof(ExampleReport))] public interface IService1 { [OperationContract] void Process(IReport report); } public interface IReport { string PrintedBy { get; set; } } public interface IApplicableDateRangeParameter { DateTime StartDate { get; set; } DateTime EndDate { get; set; } } [DataContract] public abstract class Report : IReport { [DataMember] public string PrintedBy { get; set; } } [DataContract] public class ExampleReport : Report, IApplicableDateRangeParameter { [DataMember] public DateTime StartDate { get; set; } [DataMember] public DateTime EndDate { get; set; } } The problem is that the WCF DataContractSerializer does not expose these interfaces in my client library, thus I can't write the generic report generating front-end that I plan to. Can WCF expose these interfaces, or is this a limitation of the serializer? If the latter case, then what is the canonical approach to this OO pattern? I've looked into NetDataContractSerializer but it doesn't seem to be an officially supported implementation (which means it's not an option in my project). Currently I've resigned myself to including the interfaces in a library that is common between the service and the client application, but this seems like an unnecessary extra dependency to me. Surely there is a more straightforward way to do this? I was under the impression that WCF was supposed to replace .NET remoting; checking if an object implements an interface seems to be one of the most basic features required of a remoting interface?

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• Constructor or Assignment Operator

  - by ju

  Can you help me is there definition in C++ standard that describes which one will be called constructor or assignment operator in this case: #include <iostream> using namespace std; class CTest { public: CTest() : m_nTest(0) { cout << "Default constructor" << endl; } CTest(int a) : m_nTest(a) { cout << "Int constructor" << endl; } CTest(const CTest& obj) { m_nTest = obj.m_nTest; cout << "Copy constructor" << endl; } CTest& operatorint rhs) { m_nTest = rhs; cout << "Assignment" << endl; return *this; } protected: int m_nTest; }; int _tmain(int argc, _TCHAR* argv[]) { CTest b = 5; return 0; } Or is it just a matter of compiler optimization?

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• SPWorkflowCollection on SPListItem is always empty

  - by armannvg

  Hi I'm having a problem relating to Sharepoint workflows and the associated task list. I have 2 custom workflows that we created for our product. They both use the same Task list that has a custom content type that inherits from the Task content type. Now I have a case where a running workflow has been deleted via the list has been deleted or the document, this results in orphaned tasks. I want to overwrite the Task lists OnDeleting event, so that users can cleanup their tasks so that it won't contain unneccessary orphaned tasks. So my item deleting looks like this public override void ItemDeleting(SPItemEventProperties properties) { SPListItem currentListItem = properties.ListItem; } The problem is that when I go into debug mode and check the currentListItem.Workflows.Count field then it's always 0. It doesn't matter which workflow I initiate or what task i look at, the SPWorkflowCollection returned is always empty :( I was wondering if this might be related to a bug in our custom workflow where it's not wired up properly (but it finishes correctly and tasks are deleted when a workflow is terminated) or am I looking at this the wrong way ?

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