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• Byte-Pairing for data compression

  - by user1669533

  Question about Byte-Pairing for data compression. If byte pairing converts two byte values to a single byte value, splitting the file in half, then taking a gig file and recusing it 16 times shrinks it to 62,500,000. My question is, is byte-pairing really efficient? Is the creation of a 5,000,000 iteration loop, to be conservative, efficient? I would like some feed back on and some incisive opinions please. Dave, what I read was: "The US patent office no longer grants patents on perpetual motion machines, but has recently granted at least two patents on a mathematically impossible process: compression of truly random data." I was not inferring the Patent Office was actually considering what I am inquiring about. I was merely commenting on the notion of a "mathematically impossible process." If someone has, in some way created a method of having a "single" data byte as a placeholder of 8 individual bytes of data, that would be a consideration for a patent. Now, about the mathematically impossibility of an 8 to 1 compression method, it is not so much a mathematically impossibility, but a series of rules and conditions that can be created. As long as there is the rule of 8 or 16 bit representation of storing data on a medium, there are ways to manipulate data that mirrors current methods, or creation by a new way of thinking.

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• Help me reduce code repetition in a simple jQuery function

  - by user339876

  I have built a carousel using the jQuery cycle plugin. I have 4 links that jump to relevent slides. Right now I have a chunk of code for each link. I am trying to create a single multi-purpose function. $('#features-slide0').click(function() { $('#features-slides').cycle(0); return false; }); $('#features-slide1').click(function() { $('#features-slides').cycle(1); return false; }); $('#features-slide2').click(function() { $('#features-slides').cycle(2); return false; }); $('#features-slide3').click(function() { $('#features-slides').cycle(3); return false; }); I have a rel value on each link that carries the number of the slide. How can I use that to create a single block of code that takes care of the link jump?

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• Is this a safe/valid hash method implementation?

  - by Sean

  I have a set of classes to represent some objects loaded from a database. There are a couple variations of these objects, so I have a common base class and two subclasses to represent the differences. One of the key fields they have in common is an id field. Unfortunately, the id of an object is not unique across all variations, but within a single variation. What I mean is, a single object of type A could have an id between, say, 0 and 1,000,000. An object of type B could have an id between, 25,000 and 1,025,000. This means there's some overlap of id numbers. The objects are just variations of the same kind of thing, though, so I want to think of them as such in my code. (They were assigned ids from different sets for legacy reasons.) So I have classes like this: @class BaseClass @class TypeAClass : BaseClass @class TypeBClass : BaseClass BaseClass has a method (NSNumber *)objectId. However instances of TypeA and TypeB could have overlapping ids as discussed above, so when it comes to equality and putting these into sets, I cannot just use the id alone to check it. The unique key of these instances is, essentially, (class + objectId). So I figured that I could do this by making the following hash function on the BaseClass: -(NSUInteger)hash { return (NSUInteger)[self class] ^ [self.objectId hash]; } I also implemented isEqual like so: - (BOOL)isEqual:(id)object { return (self == object) || ([object class] == [self class] && [self.objectId isEqual:[object objectId]]); } This seems to be working, but I guess I'm just asking here to make sure I'm not overlooking something - especially with the generation of the hash by using the class pointer in that way. Is this safe or is there a better way to do this?

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• two controllers in one layout, rails 3

  - by Grizlord

  Okay, I have two models, a recipe model and a category model. In my layout(application.html.erb) I have a main container div that "yields" the recipes index action. I'm trying to list all the category names as links in a side bar(also a div) by iterating over them in an unordered list. When you click one of the links it will go to the category show page which will then list all the recipes in that category. Here is how I'm trying to list the links in - <div class="container" id="categories"> <% for category in @categories %> <ul> <li><%= link_to category.name, category %></li> </ul> <% end %> </div> The problem is I get a NoMethodError - You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil.each It is not retrieving the records from the model. Any suggestions on how to get this done would be greatly appreciated. I tried to render a partial as some of the other similar posts have said but still get the same error. This is the exact error - NoMethodError in Recipes#index Showing /Users/grizlord/Rails/recipe2/app/views/layouts/application.html.erb where line #39 raised: You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil.each Extracted source (around line #39): 36: </div> 37: <div class="container" id="categories"> 38: Browse by Category 39: <% for category in @categories %> 40: <ul> 41: <li><%= link_to category.name, category %></li> 42: </ul>

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• Why does Tex/Latex not speed up in subsequent runs?

  - by Debilski

  I really wonder, why even recent systems of Tex/Latex do not use any caching to speed up later runs. Every time that I fix a single comma*, calling Latex costs me about the same amount of time, because it needs to load and convert every single picture file. (* I know that even changing a tiny comma could affect the whole structure but of course, a well-written cache format could see the impact of that. Also, there might be situations where 100% correctness is not needed as long as it’s fast.) Is there something in the language of Tex which makes this complicated or impossible to accomplish or is it just that in the original implementation of Tex, there was no need for this (because it would have been slow anyway on those large computers)? But then on the other hand, why doesn’t this annoy other people so much that they’ve started a fork which has some sort of caching (or transparent conversion of Tex files to a format which is faster to parse)? Is there anything I can do to speed up subsequent runs of Latex? Except from putting all the stuff into chapterXX.tex files and then commenting them out?

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• Question about decorator pattern and the abstract decorator class?

  - by es11

  This question was asked already here, but rather than answering the specific question, descriptions of how the decorator pattern works were given instead. I'd like to ask it again because the answer is not immediately evident to me just by reading how the decorator pattern works (I've read the wikipedia article and the section in the book Head First Design Patterns). Basically, I want to know why an abstract decorator class must be created which implements (or extends) some interface (or abstract class). Why can't all the new "decorated classes" simply implement (or extend) the base abstract object themselves (instead of extending the abstract decorator class)? To make this more concrete I'll use the example from the design patterns book dealing with coffee beverages: There is an abstract component class called Beverage Simple beverage types such as HouseBlend simply extend Beverage To decorate beverage, an abstract CondimentDecorator class is created which extends Beverage and has an instance of Beverage Say we want to add a "milk" condiment, a class Milk is created which extends CondimentDecorator I'd like to understand why we needed the CondimentDecorator class and why the class Milk couldn't have simply extended the Beverage class itself and been passed an instance of Beverage in its constructor. Hopefully this is clear...if not I'd simply like to know why is the abstract decorator class necessary for this pattern? Thanks. Edit: I tried to implement this, omitting the abstract decorator class, and it seems to still work. Is this abstract class present in all descriptions of this pattern simply because it provides a standard interface for all of the new decorated classes?

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• strange run time error message from CIImage initWithContentsOfURL

  - by Adam

  When executing the following code I receive a run time error when the code executes the second line of code. The error (which shows up in the debugger) says: [NSButton initWithContentsOfURL:]: unrecognized selector sent to instance 0x100418e10. I don't understand this message, because it looks to me (based on my source code) like the initWithContentsOfURL message is being sent to the myImage instance (of the CIImage class) ... not NSButton. Any idea what is going on? If it matters ... this code is in the Application Controller class module of an Xcode project (a Cocoa application) -- within a method that is called when I click on a button on the application window. There is only the one button on the window ... // Step1: Load the JPG file into CIImage NSURL *myURL = [NSURL fileURLWithPath:@"/Users/Adam/Documents/Images/image7.jpg"]; CIImage *myImage = [myImage initWithContentsOfURL: myURL]; if (myImage = Nil) { NSLog(@"Creating myImage failed"); return; } else { NSLog(@"Created myImage successfully"); }

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• Parsing a JSON feed from YQL using jQuery

  - by Keith

  I am using YQL's query.multi to grab multiple feeds so I can parse a single JSON feed with jQuery and reduce the number of connections I'm making. In order to parse a single feed, I need to be able to check the type of result (photo, item, entry, etc) so I can pull out items in specific ways. Because of the way the items are nested within the JSON feed, I'm not sure the best way to loop through the results and check the type and then loop through the items to display them. Here is a YQL (http://developer.yahoo.com/yql/console/) query.multi example and you can see three different result types (entry, photo, and item) and then the items nested within them: select * from query.multi where queries= "select * from twitter.user.timeline where id='twitter'; select * from flickr.photos.search where has_geo='true' and text='san francisco'; select * from delicious.feeds.popular" or here is the JSON feed itself: http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20query.multi%20where%20queries%3D%22select%20*%20from%20flickr.photos.search%20where%20user_id%3D'23433895%40N00'%3Bselect%20*%20from%20delicious.feeds%20where%20username%3D'keith.muth'%3Bselect%20*%20from%20twitter.user.timeline%20where%20id%3D'keithmuth'%22&format=json&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=

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• Overriding to_xml for collection of ActiveRecord objects

  - by Chirantan

  Okay, I know you can override the to_xml method for a single instance of ActiveRecord object and it works just fine for me. But how would I go about overriding the to_xml method for collection of objects? Suppose for Task model instance, I implemented to_xml which looks like this. def to_xml super(:methods => [:tag_list], :include => {:project => {:include => {:folder => {}}}, :folder => {}}) end Works just fine when a single task is to be serialized to xml. But when my code runs for collection of tasks, like in the following piece of code render :xml => @tasks.to_xml I get wrong number of arguments (1 for 0) /home/chirantan/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/array/conversions.rb:189:in `to_xml' /home/chirantan/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/array/conversions.rb:189:in `to_xml' /home/chirantan/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/array/conversions.rb:189:in `each' /home/chirantan/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/array/conversions.rb:189:in `to_xml' /var/lib/gems/1.8/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `call' /var/lib/gems/1.8/gems/builder-2.1.2/lib/builder/xmlbase.rb:134:in `_nested_structures' /var/lib/gems/1.8/gems/builder-2.1.2/lib/builder/xmlbase.rb:58:in `method_missing' /var/lib/gems/1.8/gems/builder-2.1.2/lib/builder/xmlbase.rb:31:in `tag!' /~/blah/app/controllers/tasks_controller.rb:412:in `completed' How do I make this work?

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• WM_NOTIFY and superclass chaining issue in Win32

  - by DasMonkeyman

  For reference I'm using the window superclass method outlined in this article. The specific issue occurs if I want to handle WM_NOTIFY messages (i.e. for custom drawing) from the base control in the superclass I either need to reflect them back from the parent window or set my own window as the parent (passed inside CREATESTRUCT for WM_(NC)CREATE to the base class). This method works fine if I have a single superclass. If I superclass my superclass then I run into a problem. Now 3 WindowProcs are operating in the same HWND, and when I reflect WM_NOTIFY messages (or have them sent to myself from the parent trick above) they always go to the outermost (most derived) WindowProc. I have no way to tell if they're messages intended for the inner superclass (base messages are supposed to go to the first superclass) or messages intended for the outer superclass (messages from the inner superclass are intended for the outer superclass). These messages are indistinguishable because they all come from the same HWND with the same control ID. Is there any way to resolve this without creating a new window to encapsulate each level of inheritance? Sorry about the wall of text. It's a difficult concept to explain. Here's a diagram. single superclass: SuperA::WindowProc() - Base::WindowProc()---\ ^--------WM_NOTIFY(Base)--------/ superclass of a superclass: SuperB::WindowProc() - SuperA::WindowProc() - Base::WindowProc()---\ ^--------WM_NOTIFY(Base)--------+-----------------------/ ^--------WM_NOTIFY(A)-----------/ The WM_NOTIFY messages in the second case all come from the same HWND and control ID, so I cannot distinguish between the messages intended for SuperA (from Base) and messages intended for SuperB (from SuperA). Any ideas?

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• activemessaging with stomp and activemq.prefetchSize=1

  - by Clint Miller

  I have a situation where I have a single activemq broker with 2 queues, Q1 and Q2. I have two ruby-based consumers using activemessaging. Let's call them C1 and C2. Both consumers subscribe to each queue. I'm setting activemq.prefetchSize=1 when subscribing to each queue. I'm also setting ack=client. Consider the following sequence of events: 1) A message that triggers a long-running job is published to queue Q1. Call this M1. 2) M1 is dispatched to consumer C1, kicking off a long operation. 3) Two messages that trigger short jobs are published to queue Q2. Call these M2 and M3. 4) M2 is dispatched to C2 which quickly runs the short job. 5) M3 is dispatched to C1, even though C1 is still running M1. It's able to dispatch to C1 because prefetchSize=1 is set on the queue subscription, not on the connection. So the fact that a Q1 message has already been dispatched doesn't stop one Q2 message from being dispatched. Since activemessaging consumers are single-threaded, the net result is that M3 sits and waits on C1 for a long time until C1 finishes processing M1. So, M3 is not processed for a long time, despite the fact that consumer C2 is sitting idle (since it quickly finishes with message M2). Essentially, whenever a long Q1 job is run and then a whole bunch of short Q2 jobs are created, exactly one of the short Q2 jobs gets stuck on a consumer waiting for the long Q1 job to finish. Is there a way to set prefetchSize at the connection level rather than at the subscription level? I really don't want any messages dispatched to C1 while it is processing M1. The other alternative is that I could create a consumer dedicated to processing Q1 and then have other consumers dedicated to processing Q2. But, I'd rather not do that since Q1 messages are infrequent--Q1's dedicated consumers would sit idle most of the day tying up memory.

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• Google App Engine how to get an object from the servlet ?

  - by Frank

  I have the following class objects in Google App Engine's dadastore, I can see them from the "Datastore Viewer " : import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.IdentityType; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; @PersistenceCapable(identityType=IdentityType.APPLICATION) public class Contact_Info_Entry implements Serializable { @PrimaryKey @Persistent(valueStrategy=IdGeneratorStrategy.IDENTITY) Long Id; public static final long serialVersionUID=26362862L; String Contact_Id="",First_Name="",Last_Name="",Company_Name="",Branch_Name="",Address_1="",Address_2="",City="",State="",Zip="",Country=""; double D_1,D_2; boolean B_1,B_2; Vector<String> A_Vector=new Vector<String>(); public Contact_Info_Entry() { } ...... } How can my java applications get the object from a servlet url ? For instance if have an instance of Contact_Info_Entry who's Contact_Id is "ABC-123", and my App Id is : nm-java When my java program accesses the url : "http://nm-java.appspot.com/Check_Contact_Info?Contact_Id=ABC-123 How will the Check_Contact_Info servlet get the object from datastore and return it to my app ? public class Check_Contact_Info_Servlet extends HttpServlet { static boolean Debug=true; public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException { } ... protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { doGet(request,response); } } Frank

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• .NET: How to pass value when subscribing to event and obtain it when the event is triggered (Dynamic

  - by Entrase

  The task is to create event handlers in runtime. I need the one method to be called with different parameter value for different events. The events and their number are only known in runtime. So I'm trying to generate dynamic methods, each of which will be assigned to some event, but in general they all just pass some value to an instance method and call it. It would be great if something similar could be done the easier way. I mean passing some value at subscribing stage and then obtaining it when the event is triggered. This is what I'm trying to do now: public class EventSource { public event EventHandler eventOne; public event EventHandler eventTwO; public event EventHandler eventThree; } public class EventListener { SubscribeForEvents() { BindingFlags flags = BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance; // Suppose we've already got EventInfo // and target source somewhere // so we can do eventInfo.AddEventHandler(target, delegate) // Now we need a delegate. int value = 42; Type tDelegate = eventInfo.EventHandlerType; // http://msdn.microsoft.com/en-us/library/ms228976(VS.95).aspx Type returnType = GetDelegateReturnType(tDelegate); DynamicMethod listener = new DynamicMethod("", null, GetDelegateParameterTypes(tDelegate), this.GetType()); ///////// Type[] callParameters = { typeof(int) }; MethodInfo method = this.GetType().GetMethod("ToCallFromDelegate", flags); ILGenerator generator = listener.GetILGenerator(); // No success in this mess. What's wrong? generator.Emit(OpCodes.Ldc_I4, value); generator.Emit(OpCodes.Call, method); generator.Emit(OpCodes.Pop); generator.Emit(OpCodes.Ret); ///////////// Delegate delegate = listener.CreateDelegate(tDelegate); eventInfo.AddEventHandler(target, delegate); // When triggered, there is InvalidProgramException } void ToCallFromDelegate(int value) { doSomething(); } }

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• Hibernate: Querying objects by attributes of inherited classes

  - by MichaelD

  Hi all, I ran into a problem with Hibernate concerning queries on classes which use inheritance. Basically I've the following class hierarchy: @Entity @Table( name = "recording" ) class Recording { ClassA attributeSet; ... } @Entity @Inheritance( strategy = InheritanceType.JOINED ) @Table( name = "classA" ) public class ClassA { String Id; ... } @Entity @Table( name = "ClassB1" ) @PrimaryKeyJoinColumn( name = "Id" ) public class ClassB1 extends ClassA { private Double P1300; private Double P2000; } @Entity @Table( name = "ClassB2" ) @PrimaryKeyJoinColumn( name = "Id" ) public class ClassB2 extends ClassA { private Double P1300; private Double P3000; } The hierarchy is already given like this and I cannot change it easily. As you can see ClassB1 and ClassB2 inherit from ClassA. Both classes contain a set of attributes which sometimes even have the same names (but I can't move them to ClassA since there are possible more sub-classes which do not use them). The Recording class references one instance of one of this classes. Now my question: What I want to do is selecting all Recording objects in my database which refer to an instance of either ClassB1 or ClassB2 with e.g. the field P1300 == 15.5 (so this could be ClassB1 or ClassB2 instances since the P1300 attribute is declared in both classes). What I tried is something like this: Criteria criteria = session.createCriteria(Recording.class); criteria.add( Restrictions.eq( "attributeSet.P1300", new Double(15.5) ) ); criteria.list(); But since P1300 is not an attribute of ClassA hibernate throws an exception telling me: could not resolve property: P1300 of: ClassA How can I tell hibernate that it should search in all subclasses to find the attribute I want to filter? Thanks MichaelD

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• Thread-safe data structure design

  - by Inso Reiges

  Hello, I have to design a data structure that is to be used in a multi-threaded environment. The basic API is simple: insert element, remove element, retrieve element, check that element exists. The structure's implementation uses implicit locking to guarantee the atomicity of a single API call. After i implemented this it became apparent, that what i really need is atomicity across several API calls. For example if a caller needs to check the existence of an element before trying to insert it he can't do that atomically even if each single API call is atomic: if(!data_structure.exists(element)) { data_structure.insert(element); } The example is somewhat awkward, but the basic point is that we can't trust the result of "exists" call anymore after we return from atomic context (the generated assembly clearly shows a minor chance of context switch between the two calls). What i currently have in mind to solve this is exposing the lock through the data structure's public API. This way clients will have to explicitly lock things, but at least they won't have to create their own locks. Is there a better commonly-known solution to these kinds of problems? And as long as we're at it, can you advise some good literature on thread-safe design? EDIT: I have a better example. Suppose that element retrieval returns either a reference or a pointer to the stored element and not it's copy. How can a caller be protected to safely use this pointer\reference after the call returns? If you think that not returning copies is a problem, then think about deep copies, i.e. objects that should also copy another objects they point to internally. Thank you.

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• BASH echo write mysql input

  - by jmituzas

  Have a bash menu where variables write to file for mysql input. heres what I have: echo "CREATE DATABASE '$mysqldbn'; #GRANT ALL PRIVILEGES ON *.* TO '$mysqlu'@'$myhost' IDENTIFIED BY '$mysqlup' WITH GRANT OPTION; GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES, LOCK TABLES ON '$mysqldbn'.* TO '$mysqlu'@'$myhost' IDENTIFIED BY '$mysqlup'; GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES, LOCK TABLES ON '$mysqldbn'.* TO '$mysqlu'@'$myip' IDENTIFIED BY '$mysqlup'; GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES, LOCK TABLES ON '$mysqldbn'.* TO '$mysqlu'@'localhost' IDENTIFIED BY '$mysqlup'; GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES< LOCK TABLES on '$mysqldbn'.* TO '$mysqlu'@'$rip' IDENTIFIED BY '$mysqlup';" > nmysql.db mysql -u root -p$mypass < nmysql.db problem is to get variables to show I had to put them in single quotes, the single quotes show up as I want for instances like '$mysqlu'@'localhost'. But how can I remove the quotes and still get to use the variable in the instance like, CREATE DATABASE '$mysqldbn' ? Double quotes wont work either, I am at a loss. Thanks in advance, Joe

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• State Animation on ListBox ItemTemplate

  - by Peanut

  I have a listbox which reads from Observable collection, and is ItemTemplate'ed: <DataTemplate x:Key="DataTemplate1"> <Grid x:Name="grid" Height="47.333" Width="577" Opacity="0.495"> <Image HorizontalAlignment="Left" Margin="10.668,8,0,8" Width="34" Source="{Binding ImageLocation}"/> <TextBlock Margin="56,8,172.334,8" TextWrapping="Wrap" Text="{Binding ApplicationName}" FontSize="21.333"/> <Grid x:Name="grid1" HorizontalAlignment="Right" Margin="0,10.003,-0.009,11.33" Width="26" Opacity="0" RenderTransformOrigin="0.5,0.5"> <Image HorizontalAlignment="Stretch" Margin="0" Source="image/downloads.png" Stretch="Fill" MouseDown="Image_MouseDown" /> </Grid> </Grid> </DataTemplate> <ListBox x:Name="searchlist" Margin="8" ItemTemplate="{DynamicResource DataTemplate1}" ItemsSource="{Binding SearchResults}" SelectionChanged="searchlist_SelectionChanged" ItemContainerStyle="{DynamicResource ListBoxItemStyle1}" /> In general, my question is "What is the easiest way to do Animation on Particular Items in this listbox As they are selected? Basically the image inside the "grid1" will be setting its opacity to 1, slowly. I would prefer to use states, but I do not know of any way to just tell blend and xaml to "When a selected item is changed, change the image opacity to 1 over a period of .3 seconds". Infact, I have been doing this in the .cs file using the VisualStateManager. Also, there is another issue. When the selected index is changed, we goto the CS file and look at SelectedItem. SelectedItem returns an instance of the Object in which it was bound to (The object inside the observable collection), and NOT an instance of the DataTemplate/ListItem etc. So how am I able to pull the correct image out of this list? State animation with VisualStateManager I can handle fine if its just normal things, but when it comes to generated listboxes' items, I'm lost. Thanks

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• How to make a increasing numbers after filenames in C?

  - by zaplec

  Hi, I have a little problem. I need to do some little operations on quite many files in one little program. So far I have decided to operate them in a single loop where I just change the number after the name. The files are all named TFxx.txt where xx is increasing number from 1 to 80. So how can I open them all in a single loop one after one? I have tried this: for(i=0; i<=80; i++) { char name[8] = "TF"+i+".txt"; FILE = open(name, r); /* Do something */ } As you can see the second line would be working in python but not in C. I have tried to do similiar running numbering with C to this program, but I haven't found out yet how to do that. The format doesn't need to be as it is on the second line, but I'd like to have some advice of how can I solve this problem. All I need to do is just be able to open many files and do same operations to them.

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• Importing data from third party datasource (open architecture design )

  - by mare

  How would you design an application (classes, interfaces in class library) in .NET when we have a fixed database design on our side and we need to support imports of data from third party data sources, which will most likely be in XML? For instance, let us say we have a Products table in our DB which has columns Id Title Description TaxLevel Price and on the other side we have for instance Products: ProductId ProdTitle Text BasicPrice Quantity. Currently I do it like this: Have the third party XML convert to classes and XSD's and then deserialize its contents into strong typed objects (what we get as a result of this process is classes like ThirdPartyProduct, ThirdPartyClassification, etc.). Then I have methods like this: InsertProduct(ThirdPartyProduct newproduct) I do not use interfaces at the moment but I would like them to. What I would like is implement something like public class Contoso_ProductSynchronization : ProductSynchronization InsertProduct(ContosoProduct p) where ProductSynchronization will be an interface or abstract class. There will most likely be many implementations of ProductSynchronization. I cannot hardcode the types - classes like ContosoProduct, NorthwindProduct might be created from the third party XML's (so preferably I would continue to use deserialization). Hopefully someone will understand what I'm trying to explain here. Just imagine you are the seller and you have numerous providers and each one uses their own proprietary XML format. I don't mind the development, which will of course be needed everytime new format appears, because it will only require 10-20 methods to be implemented, I just want the architecture to be open and support that.

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• Polymorphic urls with singular resources

  - by Brendon Muir

  I'm getting strange output when using the following routing setup: resources :warranty_types do resources :decisions end resource :warranty_review, :only => [] do resources :decisions end I have many warranty_types but only one warranty_review (thus the singular route declaration). The decisions are polymorphically associated with both. I have just a single decisions controller and a single _form.html.haml partial to render the form for a decision. This is the view code: = simple_form_for @decision, :url => [@decision_tree_owner, @decision.becomes(Decision)] do |form| The warranty_type url looks like this (for a new decision): /warranty_types/2/decisions whereas the warranty_review url looks like this: /admin/warranty_review/decisions.1 I think because the warranty_review id has no where to go, it's just getting appended to the end as an extension. Can someone explain what's going on here and how I might be able to fix it? I can work around it by trying to detect for a warranty_review class and substituting @decision_tree_owner with :warranty_review and this generates the correct url, but this is messy. I would have thought that the routing would be smart enough to realise that warranty_review is a singular resource and thus discard the id from the URL. This is Rails 3 by the way :)

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• Ordering by a max or a min from another table

  - by Paul Tomblin

  I have a table that consists of a unique id, and a few other attributes. It holds "schedules". Then I have another table that holds a list of all the times each schedule has or will "fire". This isn't the exact schema, but it's close: create table schedule ( id varchar(40) primary key, attr1 int, attr2 varchar(20) ); create table schedule_times ( id varchar(40) foreign key schedule(id), fire_date date ); I want to query the schedule table, getting the attributes and the next and previous fire_dates, in Java, sometimes ordering on one of the attributes, but sometimes ordering on either previous fire_date or the next fire_date. Ordering by the attributes is easy, I just stick an "order by" into the string while I'm building my prepared statement. I'm not even sure how to go about selecting the last fire_date and the next one in a single query - I know that I can find the next fire_date for a given id by doing a SELECT min(fire_date) FROM schedule_times WHERE id = ? AND fire_date > sysdate; and the similar thing for previous fire_date using max() and fire_date < sysdate. I'm just drawing a blank on how to incorporate that into a single select from the schedule so I can get both next and previous fire_date in one shot, and also how to order by either of those attributes.

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• Unit Testing-- fundamental goal?

  - by David

  Me and my co-workers had a bit of a disagreement last night about unit testing in our PHP/MySQL application. Half of us argued that when unit testing a function within a class, you should mock everything outside of that class and its parents. The other half of us argued that you SHOULDN'T mock anything that is a direct dependancy of the class either. The specific example was our logging mechanism, which happened through a static Logging class, and we had a number of Logging::log() calls in various locations throughout our application. The first half of us said the Logging mechanism should be faked (mocked) because it would be tested in the Logging unit tests. The second half of us argued that we should include the original Logging class in our unit test so that if we make a change to our logging interface, we'll be able to see if it creates problems in other parts of the application due to failing to update the call interface. So I guess the fundamental question is-- do unit tests serve to test the functionality of a single unit in a closed environment, or show the consequences of changes to a single unit in a larger environment? If it's one of these, how do you accomplish the other?

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• Visual Studio Unit Test failure to start

  - by swmi

  Hi, I am having an issue when starting the tests under debug mode in Visual Studio 2008 Team Test where it gives the following error: "Failed to queue test run '{user@machinename}': Object reference not set to an instance of an object." I googled for the error but no joy. Don't even understand what it means as it is too brief. Has anyone come across this? Note that I can run tests fine if I am not debugging and I get the same error irrespective of the test I run. Thank you, Swati ETA: Being new to Visual Studio Team Test, I didn't know there was a better exception log then what I was seeing. Anyhow, here it is: <Exception> System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.VisualStudio.TestTools.TestCaseManagement.QualityToolsPackage. ShowToolWindow [T](T&amp; toolWindow, String errorMessage, Boolean show) at Microsoft.VisualStudio.TestTools.TestCaseManagement.QualityToolsPackage. OpenTestResultsToolWindow() at Microsoft.VisualStudio.TestTools.TestCaseManagement.SolutionIntegrationManager. DebugTarget(DebugInfo debugInfo, Boolean prepareEnvironment) at Microsoft.VisualStudio.TestTools.TestManagement.DebugProcessLauncher.Launch( String exeFileName, String args, String workingDir, EventHandler processExitedHandler, Process&amp; process) at Microsoft.VisualStudio.TestTools.TestManagement.LocalControllerProxy.StartProcess( TestRun run) at Microsoft.VisualStudio.TestTools.TestManagement.LocalControllerProxy.RestartProcess( TestRun run) at Microsoft.VisualStudio.TestTools.TestManagement.LocalControllerProxy.PrepareProcess( TestRun run) at Microsoft.VisualStudio.TestTools.TestManagement.LocalControllerProxy. InitializeController(TestRun run) at Microsoft.VisualStudio.TestTools.TestManagement.ControllerProxy.QueueTestRunWorker( Object state) </Exception>

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• Cannot connect to SQL Server from ASP.NET MVC app

  - by Dan Fergus

  I have an ASP.NET MVC app that has on a hosted server for over a year, connecting to SQL Server. I've had to change hosting services, the new one supports MVC 1.0. I've also moved a non MVC ASP app to the same hosting service. Now, MY MVC based app retturnes this error when I try to validate a user login. A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) Now, the non-MVC app can access the exact same database and authenticate users just fine. The MVC app, when run from my dev box connects fine. It also run/connects/authenticates without problem when I install and run the site from an internal SQL 2008 server running IIS 7. I, along with the hosting support techs, am at a loss how the exact same connect string works every where except on the hosted server, and only when run from inside an ASP.NET MVC web app. Any ideas would be greatly appreciated.

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• Disadvantages of MySQL Row Locking

  - by Nyxynyx

  I am using row locking (transactions) in MySQL for creating a job queue. Engine used is InnoDB. SQL Query START TRANSACTION; SELECT * FROM mytable WHERE status IS NULL ORDER BY timestamp DESC LIMIT 1 FOR UPDATE; UPDATE mytable SET status = 1; COMMIT; According to this webpage, The problem with SELECT FOR UPDATE is that it usually creates a single synchronization point for all of the worker processes, and you see a lot of processes waiting for the locks to be released with COMMIT. Question: Does this mean that when the first query is executed, which takes some time to finish the transaction before, when the second similar query occurs before the first transaction is committed, it will have to wait for it to finish before the query is executed? If this is true, then I do not understand why the row locking of a single row (which I assume) will affect the next transaction query that would not require reading that locked row? Additionally, can this problem be solved (and still achieve the effect row locking does for a job queue) by doing a UPDATE instead of the transaction? UPDATE mytable SET status = 1 WHERE status IS NULL ORDER BY timestamp DESC LIMIT 1

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