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  • Are document-oriented databases any more suitable than relational ones for persisting objects?

    - by Owen Fraser-Green
    In terms of database usage, the last decade was the age of the ORM with hundreds competing to persist our object graphs in plain old-fashioned RMDBS. Now we seem to be witnessing the coming of age of document-oriented databases. These databases are highly optimized for schema-free documents but are also very attractive for their ability to scale out and query a cluster in parallel. Document-oriented databases also hold a couple of advantages over RDBMS's for persisting data models in object-oriented designs. As the tables are schema-free, one can store objects belonging to different classes in an inheritance hierarchy side-by-side. Also, as the domain model changes, so long as the code can cope with getting back objects from an old version of the domain classes, one can avoid having to migrate the whole database at every change. On the other hand, the performance benefits of document-oriented databases mainly appear to come about when storing deeper documents. In object-oriented terms, classes which are composed of other classes, for example, a blog post and its comments. In most of the examples of this I can come up with though, such as the blog one, the gain in read access would appear to be offset by the penalty in having to write the whole blog post "document" every time a new comment is added. It looks to me as though document-oriented databases can bring significant benefits to object-oriented systems if one takes extreme care to organize the objects in deep graphs optimized for the way the data will be read and written but this means knowing the use cases up front. In the real world, we often don't know until we actually have a live implementation we can profile. So is the case of relational vs. document-oriented databases one of swings and roundabouts? I'm interested in people's opinions and advice, in particular if anyone has built any significant applications on a document-oriented database.

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  • The CLR has been unable to transition from COM context [...] for 60 seconds

    - by BlueRaja The Green Unicorn
    I am getting this error on code that used to work. I have not changed the code. Here is the full error: The CLR has been unable to transition from COM context 0x3322d98 to COM context 0x3322f08 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations. And here is the code that caused it: var openFileDialog1 = new System.Windows.Forms.OpenFileDialog(); openFileDialog1.DefaultExt = "mdb"; openFileDialog1.Filter = "Management Database (manage.mdb)|manage.mdb"; //Stalls indefinitely on the following line, then gives the CLR error //one minute later. The dialog never opens. if(openFileDialog1.ShowDialog() == DialogResult.OK) { .... } Yes, I am sure the dialog is not open in the background, and no, I don't have any explicit COM code or unmanaged marshalling or multithreading. I have no idea why the OpenFileDialog won't open - any ideas?

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  • Factorial in Prolog and C++

    - by Joshua Green
    I would like to work out a number's factorial. My factorial rule is in a Prolog file and I am connecting it to a C++ code. Can someone tell me what is wrong with my C++ interface please? % factorial.pl factorial( 1, 1 ):- !. factorial( X, Fac ):- X > 1, Y is X - 1, factorial( Y, New_Fac ), Fac is X * New_Fac. // factorial.cpp # headerfiles term_t t1; term_t t2; term_t goal_term; functor_t goal_functor; int main( int argc, char** argv ) { argc = 4; argv[0] = "libpl.dll"; argv[1] = "-G32m"; argv[2] = "-L32m"; argv[3] = "-T32m"; PL_initialise(argc, argv); if ( !PL_initialise(argc, argv) ) PL_halt(1); PlCall( "consult(swi('plwin.rc'))" ); PlCall( "consult('factorial.pl')" ); cout << "Enter your factorial number: "; long n; cin >> n; PL_put_integer( t1, n ); t1 = PL_new_term_ref(); t2 = PL_new_term_ref(); goal_term = PL_new_term_ref(); goal_functor = PL_new_functor( PL_new_atom("factorial"), 2 ); PL_put_atom( t1, t2 ); PL_cons_functor( goal_term, goal_functor, t1, t2 ); PL_halt( PL_toplevel() ? 0 : 1 ); }

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  • What is there so useful in the Decorator Pattern? My example doesn't work

    - by Green
    The book says: The decorator pattern can be used to extend (decorate) the functionality of a certain object I have a rabbit animal. And I want my rabbit to have, for example, reptile skin. Just want to decorate a common rabbit with reptile skin. I have the code. First I have abstract class Animal with everythig that is common to any animal: abstract class Animal { abstract public function setSleep($hours); abstract public function setEat($food); abstract public function getSkinType(); /* and more methods which for sure will be implemented in any concrete animal */ } I create class for my rabbit: class Rabbit extends Animal { private $rest; private $stomach; private $skinType = "hair"; public function setSleep($hours) { $this->rest = $hours; } public function setFood($food) { $this->stomach = $food; } public function getSkinType() { return $this->$skinType; } } Up to now everything is OK. Then I create abstract AnimalDecorator class which extends Animal: abstract class AnimalDecorator extends Animal { protected $animal; public function __construct(Animal $animal) { $this->animal = $animal; } } And here the problem comes. Pay attention that AnimalDecorator also gets all the abstract methods from the Animal class (in this example just two but in real can have many more). Then I create concrete ReptileSkinDecorator class which extends AnimalDecorator. It also has those the same two abstract methods from Animal: class ReptileSkinDecorator extends AnimalDecorator { public function getSkinColor() { $skin = $this->animal->getSkinType(); $skin = "reptile"; return $skin; } } And finaly I want to decorate my rabbit with reptile skin: $reptileSkinRabbit = ReptileSkinDecorator(new Rabbit()); But I can't do this because I have two abstract methods in ReptileSkinDecorator class. They are: abstract public function setSleep($hours); abstract public function setEat($food); So, instead of just re-decorating only skin I also have to re-decorate setSleep() and setEat(); methods. But I don't need to. In all the book examples there is always ONLY ONE abstract method in Animal class. And of course it works then. But here I just made very simple real life example and tried to use the Decorator pattern and it doesn't work without implementing those abstract methods in ReptileSkinDecorator class. It means that if I want to use my example I have to create a brand new rabbit and implement for it its own setSleep() and setEat() methods. OK, let it be. But then this brand new rabbit has the instance of commont Rabbit I passed to ReptileSkinDecorator: $reptileSkinRabbit = ReptileSkinDecorator(new Rabbit()); I have one common rabbit instance with its own methods in the reptileSkinRabbit instance which in its turn has its own reptileSkinRabbit methods. I have rabbit in rabbit. But I think I don't have to have such possibility. I don't understand the Decarator pattern right way. Kindly ask you to point on any mistakes in my example, in my understanding of this pattern. Thank you.

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  • Unhandled Exception error message

    - by Joshua Green
    Does anyone know why including a term such as: t = PL_new_term_ref(); would cause an Unhandled Exception error message: 0xC0000005: Access violation reading location 0x0000000c. (Visual Studio 2008) I have a header file: class UserTaskProlog : public ArAction { public: UserTaskProlog( const char* name = " sth " ); ~UserTaskProlog( ); AREXPORT virtual ArActionDesired *fire( ArActionDesired currentDesired ); private: term_t t; }; and a cpp file: UserTaskProlog::UserTaskProlog( const char* name ) : ArAction( name, " sth " ) { char** argv; argv[ 0 ] = "libpl.dll"; PL_initialise( 1, argv ); PlCall( "consult( 'myProg.pl' )" ); } UserTaskProlog::~UserTaskProlog( ) { } ArActionDesired *UserTaskProlog::fire( ArActionDesired currentDesired ) { cout << " something " << endl; t = PL_new_term_ref( ); } Without t=PL_new_term_ref() everything works fine, but when I start adding my Prolog code (declarations first, such as t=PL_new_term_ref), I get this Access Violation error message. I'd appreciate any help. Thanks,

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  • Loop colours from variables for graphics.py [Python 3.2]

    - by user1056548
    I am creating a graphics program that draws 100 x 100 squares next to each other depending on the user-specified grid size. The user also inputs 4 colours for the squares to be coloured (e.g. if they enter red,green,blue,yellow the squares will be coloured in that order, repeating the colours). Is it possible to loop the colours from the variables the user has given? Here is what I have so far: def main(): print ("Please enter four comma seperated colours e.g.: 'red,green,blue,yellow'\n\ Allowed colours are: red, green, blue, yellow and cyan") col1, col2, col3, col4 = input("Enter your four colours: ").split(',') win = GraphWin ("Squares", 500, 500) colours = [col1, col2, col3, col4] drawSquare (win, col1, col2, col3, col4, colours) win.getMouse() win.close() def drawSquare(win, col1, col2, col3, col4, colours): for i in range (4): for j in range (len(colours)): colour = colours[j] x = 50 + (i * 50) circle = Circle (Point (x,50), 20) circle.setFill(colour) circle.draw(win) I think I should be using a list in some way, but can't work out exactly how to do it. Can anybody help?

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  • Color blindness: Are you aware of it? Do you design for it?

    - by User
    I'm curious whether many of us who do design or take design decisions have ever heard of this problem. I'm aware there are dangerous color combinations, like green + red. This is probably one of the most popular cases of color blindness. If you have green text on a red background and vice versa some people won't see anything. I've also seen in practice that green text on a blue background was not seen by one guy. What other color compositions should be avoided, and how often these cases are to be expected? Let us make some ranging by encounter probability who has the numbers. Addition: I've just remembered one very bad example that causes problems to just about everyone - blue text on a black background. It's unreadable for all intents and purposes. Never could understand what could possibly compel a web master to use this color combination...

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  • C/C++ enum and char * array

    - by Eric M
    Ran accross the following code in an article and didn't think it was standard C/C++ syntax for the char* array. As a test, both Visual C++ (visual studio 2005) and C++ Builder Rad XE both reject the 2nd line. Without using #defines, anyone have any tricks/tips for keeping enums and a string array sort of in sync without resorting to STL ? More of a curiosity question. enum TCOLOR { RED, GREEN, BLUE }; char *TNCOLOR[] = { [RED]="Red", [GREEN]="Green", [BLUE]="Blue" }; as an aside, the article this came from is quite old and I believe this might work under GCC but have not tested.

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  • Float over two elements

    - by eWolf
    My problem is rather complex to explain, so I'll show you an example: http://ewolf.bplaced.de/misc/float.htm I want to have a floated element (the blue box) to be be placed over two other elements (red and green) and I want the whole thing to be fixed-width and centered (done by the box with the black border) while the background of the red and green box should fill the whole width. I'm actually not quite sure if the way I've done it now is XHTML/CSS valid, but it works - at least in Firefox. In IE6, the green box expands to fit the whole blue box - how can I fix this in IE6 or find another solution to show it correctly in all browsers?

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  • By-name repeated parameters

    - by Green Hyena
    How to pass by-name repeated parameters in Scala? The following code fails to work: scala> def foo(s: (=> String)*) = { <console>:1: error: no by-name parameter type allowed here def foo(s: (=> String)*) = { ^ Is there any other way I could pass a variable number of by name parameters to the method?

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  • MySQL: Count occurrences of known (or enumerated) distinct values

    - by Eilidh
    After looking at how to count the occurrences of distinct values in a field, I am wondering how to count the occurrences of each distinct value if the distinct values are known (or enumerated). For example, if I have a simple table - TrafficLight Colour ------------ ------ 1 Red 2 Amber 3 Red 4 Red 5 Green 6 Green where one column (in this case Colour) has known (or enumerated) distinct values, how could I return the count for each colour as a separate value, rather than as an array, as in the linked example. To return an array with a count of each colour (using the same method as in the linked example), the query would be something like SELECT Colour COUNT(*) AS ColourCount FROM TrafficLights GROUP BY Colour, and return an array - Colour ColourCount ------ ----------- Red 3 Amber 1 Green 2 What I would like to do is to return the count for each Colour AS a separate total (e.g. RedCount). How can I do this?

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  • Separating an Array into a comma seperated string with quotes

    - by user548744
    I'm manually building an SQL query where I'm using an Array in the params hash for an SQL IN statement, like: ("WHERE my_field IN('blue','green','red')"). So I need to take the contents of the array and output them into a string where each element is single quoted and comma seperated (and with no ending comma). So if the array was: my_array = ['blue','green','red'] I'd need a string that looked like: "'blue','green','red'" I'm pretty new to Ruby/Rails but came up with something that worked: if !params[:colors].nil? @categories_array = params[:colors][:categories] @categories_string ="" for x in @categories_array @categories_string += "'" + x + "'," end @categories_string.chop! #remove the last comma end So, I'm good but curious as to what a proper and more consise way of doing this would look like? Thanks

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  • WinForm-style Invoke() in unmanaged C++

    - by Matt Green
    I've been playing with a DataBus-type design for a hobby project, and I ran into an issue. Back-end components need to notify the UI that something has happened. My implementation of the bus delivers the messages synchronously with respect to the sender. In other words, when you call Send(), the method blocks until all the handlers have called. (This allows callers to use stack memory management for event objects.) However, consider the case where an event handler updates the GUI in response to an event. If the handler is called, and the message sender lives on another thread, then the handler cannot update the GUI due to Win32's GUI elements having thread affinity. More dynamic platforms such as .NET allow you to handle this by calling a special Invoke() method to move the method call (and the arguments) to the UI thread. I'm guessing they use the .NET parking window or the like for these sorts of things. A morbid curiosity was born: can we do this in C++, even if we limit the scope of the problem? Can we make it nicer than existing solutions? I know Qt does something similar with the moveToThread() function. By nicer, I'll mention that I'm specifically trying to avoid code of the following form: if(! this->IsUIThread()) { Invoke(MainWindowPresenter::OnTracksAdded, e); return; } being at the top of every UI method. This dance was common in WinForms when dealing with this issue. I think this sort of concern should be isolated from the domain-specific code and a wrapper object made to deal with it. My implementation consists of: DeferredFunction - functor that stores the target method in a FastDelegate, and deep copies the single event argument. This is the object that is sent across thread boundaries. UIEventHandler - responsible for dispatching a single event from the bus. When the Execute() method is called, it checks the thread ID. If it does not match the UI thread ID (set at construction time), a DeferredFunction is allocated on the heap with the instance, method, and event argument. A pointer to it is sent to the UI thread via PostThreadMessage(). Finally, a hook function for the thread's message pump is used to call the DeferredFunction and de-allocate it. Alternatively, I can use a message loop filter, since my UI framework (WTL) supports them. Ultimately, is this a good idea? The whole message hooking thing makes me leery. The intent is certainly noble, but are there are any pitfalls I should know about? Or is there an easier way to do this?

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  • Wrapper class for HttpGet / Post in Java?

    - by Tim Green
    Hi, Sorry, I'm quite new to Java. I've stumbled across HttpGet and HttpPost which seem to be perfect for my needs, but a little long winded. I have written a rather bad wrapper class, but does anyone know of where to get a better one? Ideally, I'd be able to do String response = fetchContent("http://url/", postdata); where postdata is optional. Thanks!

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  • data structure for counting frequencies in a database table-like format

    - by user373312
    i was wondering if there is a data structure optimized to count frequencies against data that is stored in a database table-like format. for example, the data comes in a (comma) delimited format below. col1, col2, col3 x, a, green x, b, blue ... y, c, green now i simply want to count the frequency of col1=x or col1=x and col2=green. i have been storing the data in a database table, but in my profiling and from empirical observation, database connection is the bottle-neck. i have tried using in-memory database solutions too, and that works quite well; the only problem is memory requirements and quirky init/destroy calls. also, i work mainly with java, but have experience with .net, and was wondering if there was any api to work with "tabular" data in a linq way using java. any help is appreciated.

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  • Get rid of all user data of Android application after bigger update

    - by Johe Green
    Hi, I completely revamped an app. Tested it for a while on my device and emulator. The app worked fine. However when I updated the app through the Android market, my users experienced crashes. Since there is no way to properly debug this procedure I asume the crash is caused by old data which is not being removed from the device (probably from the onsavedstate bundle?!). Is there a way to do a "clean/total" reinstall without having the user to do it manually? Best Regards Johe

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  • How to test routes that don't include controller?

    - by Darren Green
    I'm using minitest in Rails to do testing, but I'm running into a problem that I hope a more seasoned tester can help me out with because I've tried looking everywhere for the answer, but it doesn't seem that anyone has run into this problem or if they have, they opted for an integration test. Let's say I have a controller called Foo and action in it called bar. So the foo_controller.rb file looks like this: class FooController < ApplicationController def bar render 'bar', :layout => 'application' end end The thing is that I don't want people to access the "foo/bar" route directly. So I have a route that is get 'baz' => 'foo#bar'. Now I want to test the FooController: require 'minitest_helper' class FooControllerTest < ActionController::TestCase def test_should_get_index get '/baz' end end But the test results in an error that No route matches {:controller=>"foo", :action=>"/baz"}. How do I specify the controller for the GET request? Sorry if this is a dumb question. It's been very hard for me to find the answer.

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  • XForms: set default selection in dropdown in binding

    - by Purni
    I have a main instance named 'myinstance' which has the element . Color can be 'Red', 'Blue', 'Green' or ''Yellow'. The colors are populated in a drop-down from another instance called 'colorsinstance'. When my form loads, I want the default in the dropdown to be set to 'Green' in the nodeset binding. <instance id="colorsinstance"> <items> <item label="Color1" value="Red"/> <item label="Color2" value="Blue"/> <item label="Color3" value="Green"/> <item label="Color4" value="Yellow"/> </items> </instance> Main instance binding is as follows: <xforms:bind nodeset="instance('myinstance')"> <xforms:bind nodeset="./color" required="true()"/> </xforms:bind>

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  • Overloading on return type ???

    - by Green Hyena
    scala> val shares = Map("Apple" -> 23, "MicroSoft" -> 50, "IBM" -> 17) shares: scala.collection.immutable.Map[java.lang.String,Int] = Map(Apple -> 23, MicroSoft -> 50, IBM -> 17) scala> val shareholders = shares map {_._1} shareholders: scala.collection.immutable.Iterable[java.lang.String] = List(Apple, MicroSoft, IBM) scala> val newShares = shares map {case(k, v) => (k, 1.5 * v)} newShares: scala.collection.immutable.Map[java.lang.String,Double] = Map(Apple -> 34.5, MicroSoft -> 75.0, IBM -> 25.5) From this example it seems like the map method is overloaded on return type. Overloading on return type is not possible right? Would somebody please explain what's going on here?

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  • Should I dispose GDI+ object before its creation?

    - by serhio
    Should I dispose GDI+ object before its creation? Is recommended to always Dispose GDI+ object after using it. by e.g. Pen p = new Pen(Color.Green); // use 'p' p.Dispose(); now, if I have this situation: Pen p = new Pen(Color.Green); // use green 'p' p = new Pen(Color.Red); // Should I Dispose my 'p' first? // use red 'p' p.Dispose();

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  • wrap text around image control in C#.Net

    - by Ravi
    Hi, I am working on C#.DotNet windows application project, here i am using Infragistics control. In this project i want to add image over text control. This image contains two portion, 35% of image have white color another 65% of image have green color.In this image 2nd portion(green color) i have to display dynamic string , this string size may dynamically updating. But this string dont go first portion(white color) of image. For that i am using UltraLabel control. I have add image in UltraLabel ImageBackground property and TextHAlign set as Right. But here small 15 charecter string means appear only second portion(green color), 20 charecter string means appeaer second & first portion. I don't want to display first portion of image. Thanks

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  • SEO URL Structure

    - by Neil
    Based on the following example URL structure: mysite.com/mypage.aspx?a=red&b=green&c=blue Pages in the application use ASP.net user controls and some of these controls build a query string. To prevent duplicate keys being created e.g. &pid=12&pid=10, I am researching methods of rewriting the URL: a) mysite.com/mypage.aspx/red/green/blue b) mysite.com/mypage.aspx?controlname=a,red|b,green|c,blue Pages using this structure would be publishing content that I would like to get indexed and ranked - articles and products (8,000 products to start, with thousands more being added later) My gut instinct tells me to go with the first method, but would it would be overkill to add all that infrastructure if the second method will accomplish my goal of getting pages indexed AND ranked. So my question, looking at the pro's and con's, Google Ranking, time to implement etc. which method should I use? Thanks!

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  • Java combine parents of two large inheritance chains

    - by Soylent Green
    I have two parent classes in a huge project, let's say ClassA and ClassB. Each class has many subclasses, which in turn have many subclasses, which in turn have many subclasses, etc. My task is to "marry" these two "families" so that both inherit from a SINGLE parent. I need to essentially make ClassA and ClassB one class (parent) to both of their combined subclasses (children). ClassA and ClassB both currently implement Serializable. I am currently trying to make both inheritance chains inherit from ClassA, and then copy all functions and data members from ClassB into ClassA. This is tedious, and I think a terrible solution. What would be the CORRECT way to solve this problem?

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  • What does "Select Distinct Null As xxxxx" mean?

    - by Soylent Green
    Background: I am mapping Sybase stored procedure return values to java objects using Spring. For example I map a Sybase datatype of varchar as a String type in Java, and a Sybase datatype of int as an int type in Java, etc. I have come across the following code in one of the stored procedures: SELECT DISTINCT A.Col1 AS val1, A.Col2 AS val2, NULL AS someVal, A.col3 AS val3, ... A.col9 AS val9 FROM #SomeTable A ORDER BY Col2, Col3 I have 2 related questions: What does Null mean in this scenario? I am confused as to what is happening here. I am able to determine the data type of Col1, Col2, etc. of course by looking at the table definition of Table A defined earlier in the stored procedure. Thus I know what datatype I can define in my Java object for val1, val2, etc.. But what about "someVal"? What datatype mapping am I supposed to perform for this Null value? I am fairly inexperienced in SQL. Perhaps the answer is much simpler than I realize.

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