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• Count the number of ways in which a number 'A' can be broken into a sum of 'B' numbers such that all numbers are co-prime to 'C'

  - by rajneesh2k10

  I came across the solution of a problem which involve dynamic-programming approach, solved using a three dimensional matrix. Link to actual problem is: http://community.topcoder.com/stat?c=problem_statement&pm=12189&rd=15177 Solution to this problem is here under MuddyRoad2: http://apps.topcoder.com/wiki/display/tc/SRM+555 In the last paragraph of explanation, author describes a dynamic programming approach to count the number of ways in which a number 'A' can be broken into a sum of 'B' numbers (not necessarily different), such that every number is co-prime to 3 and the order in which these numbers appear does matter. I am not able to grasp that approach. Can anyone help me understand how DP is acting here. I can't understand what is a state here and how it is derived from the previous state.

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• EntityFramework how to Override properties

  - by plotnick

  I've just started using EF in VS2010. That thing is just amazin'. I frankly can't understand something. For example I have EntityType with property, they generated from database structure. Now, I have to simply override that property in my code. I don't need to save value of the property back into DB, but everytime when it gets read from DB it should be substituted with run-time calculated value. Of course I can create derived class based on my EntityType but I've tried and found kinda difficulties, I'm not sure this is kinda right way to do. Anyway even when I try to change the whole EntityType to Abstract, damn Visual Studio doesn't want to validate that and says something like: "Error 2078: The EntityType 'AssetsModel.Asset' is Abstract and can be mapped only using IsTypeOf." "Error 2063: At least one property must be mapped in the set mapping for 'Assets'" What the hell is this suppose to mean I dunno.. Any ideas gentlemen?

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• Managing memory of polymorphic timed events with DLL

  - by Milo

  Here is my issue. My Gui library that I made supports timed events. Basically, I have a class called TimedEvent which users inherit from. They then do: addTimedEvent(new DerivedTimedEvent(...)); However given the nature of timed events, I manage the memory afterwards. So when the timed event has done its thing, my library calls delete on it. Although it runs fine, that is because the exe and the library were both built with msvc 2008. I think I might have trouble if I have 2 versions of the runtime, one for the lib, and one for the exe. What can I do to fix this? I can't create a factory because the derived type is on the exe side of things. I also cannot ask the user to call delete since they might not have a way to keep track of time, or know if the event was delayed for whatever reason. Thanks

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• SQL where clasue to work with Group by clasue after performing a count()

  - by Matt

  Tried my usual references at w3schools and google. No luck I'm trying to produce the following results. QTY is a derived column | Position | QTY -------------------- 1 Clerk 2 2 Mgr 2 Here's what I'm not having luck with: SELECT Position, Count(position) AS 'QTY' FROM tblemployee Where ('QTY' != 1) GROUP BY Position I know that my Position is set up as varchar(255) Count produces a integer data and my where clasue is accurate so that leads me to believe that that Count() is jamming me up. Please throw up an example so I can reference later. Thanks for the help!

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• How can I check the type of an object against a list of types?

  - by RookieRick

  Given a collection IEnumerable<Type> supportedTypes What's the best way to check whether a given object is one of those types (or a derived type)? My first instinct was to do something like: // object target is a parameter passed to the method in which I'm doing this. if (supportedTypes.Count( supportedType => target is supportedType ) > 0) { // Yay my object is of a supported type!!! } ..but that doesn't seem to be working. Can I not use the "is" keyword in a lambda expression like this?

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• How to map inheritance with property returned other inheritance?

  - by dario-g

  Hi I have abstract class Vehicle and two classes that derive from: Car and ForkLift. public abstract class Vehicle { public EngineBase Engine { get; set; } } public class Car : Vehicle { public GasEngine Engine { get; set; } } public class ForkLift : Vehicle { public ElectricEngine Engine { get; set; } } and Engine clasess: public abstract class Engine { } public class GasEngine : Engine { } public class ElectricEngine : Engine { } Engines are mapped with "table per class hierarchy". With Vehicles I want to use the same pattern. How to map Engine class and derived with that Engine property?

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• View / ViewModel - what is the sense (in a WPF control)?

  - by TomTom

  Not as funny as it sounds. Normally the View / ViewModel should decouple the presentation from the business logic. Good. Now, a Control in WPF is basically invisible unless made different (with the exceptions of UserControl and Window that have XAML directly attached). The Style is putting in the "visual presentation" - which basically means a Control does not need a view mechanism as WPF already has one? In addition. the ViewModel is actually part of the Control, or? Just fighting with that stuff. I know in ASP.NET, WinForms the separation makes a lot of sense - but there, basically, controls HAVE an intrinsic look. In WPF, I have some where it makes sense (derived from UserControl), but for the majority of the controls I write, the View & ViewModel look like pretty much totally superflous thanks to the already presenting view mechanism.

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• MATLAB pdist function

  - by James

  Hi, I am using the pdist command to find the distance between x and y coordinates stored in a matrix. X = [100 100; 0 100; 100 0; 500 400; 300 600;]; D = pdist(X,'euclidean') Which returns a 15 element vector. : [0.734979755525412 3.40039811339820 2.93175207511321 1.83879677592575 2.40127440268306 2.75251513299386 2.21488402640753 1.10610649500317 1.81674017301699 0.903207751535635 1.99116952754924 1.05069952386082 1.24122819418333 1.08583377275532 1.38729428638035] Is there a way to associate these distances with the coordinates they were derived from, i.e. store them in a matrix with the general row form: [Length xcoordinate1 ycoordinate1 xcoordinate2 ycoordinate2] Where there is a row for each length found? Thanks in advance

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• Multiple selection in a TreeView

  - by Frederick

  I am using a Windows Forms TreeView control in my program. I would like to allow the user to select multiple nodes at the same level by dragging their mouse pointer around (also called a "lasso" selection). I don't think a standard TreeView allows that. My question is what would be the best way to achieve this? Do I have to write custom selection behaviour of my own in perhaps a custom or derived control? Where do I start? I don't need a detailed explanation. Just a small nudge in the right direction.

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• [C++] Boost test: catch user defined exceptions

  - by user231536

  If I have user defined exceptions in my code, I can't get Boost test to consider them as failures. For example, BOOST_AUTO_TEST_CASE_EXPECTED_FAILURES(MyTest,1) BOOST_AUTO_TEST_CASE(MyTest) { // code which throws user defined exception, not derived from std::exception. } I get a generic message: Caught exception: .... unknown location(0):.... It does not recognize this error as a failure since it is not a std::exception. So it does not honor the expected_failures clause. How do I enforce that the piece of code should always throw an exception? THis seems to be a useful thing to want. In case future code changes cause the code to pass and the exception is not thrown, I want to know that.

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• update value of a variable outside a class in VB.NET

  - by dpp

  I have a class derived from a Form, it has textbox for username and password and an OK button. I want it to behave like an InputBox so I can use it like this: Dim Username As String = "" Dim Password As String = "" Dim authorization As New Authorization(Username, Password) authorization.ShowDialog() 'The user will click OK and I will expect the Username and Password to change based on the user input MsgBox(Username & " " & Password) The Authorization class: Public Class Authorization Dim RefUsername As String Dim RefPassword As String Public Sub New(ByRef Username As String, ByRef Password As String) InitializeComponent() RefUsername = Username 'I'm trying to pass reference instead of value RefPassword = Password 'I'm trying to pass reference instead of value End Sub Private Sub OKButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles AuthorizeButton.Click RefUsername = Username.Text 'I'm trying to change value of variable outside the class RefPassword = Password.Text 'I'm trying to change value of variable outside the class Me.Close() End Sub End Class In short, I want to change the value of variables outside the class when the user clicks the OK, how am I going to accomplish that?

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• Why would I want to have a non-standard attribute?

  - by dontWatchMyProfile

  The documentation on Core Data entities says: You might implement a custom class, for example, to provide custom accessor or validation methods, to use non-standard attributes, to specify dependent keys, to calculate derived values, or to implement any other custom logic. I stumbled over the non-standard attributes claim. It's just a guess: If my attribute is anything other than NSString, NSNumber or NSDate I will want to have a non-standard Attribute with special setter and getter methods? So, for example, if I wanted to store an image, this would be a non-standard Attribute with type NSData and a special method, say -(void)setImageWithFileURL:(NSURL*)url which then pulls the image data from the file, puts in in an NSData and assigns it to core data? Or did I get that wrong?

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• AppEngine: Can I write a Dynamic property (db.Expando) with a name chosen at runtime?

  - by MarcoB

  If I have an entity derived from db.Expando I can write Dynamic property by just assigning a value to a new property, e.g. "y" in this example: class MyEntity(db.Expando): x = db.IntegerProperty() my_entity = MyEntity(x=1) my_entity.y = 2 But suppose I have the name of the dynamic property in a variable... how can I (1) read and write to it, and (2) check if the Dynamic variable exists in the entity's instance? e.g. class MyEntity(db.Expando): x = db.IntegerProperty() my_entity = MyEntity(x=1) # choose a var name: var_name = "z" # assign a value to the Dynamic variable whose name is in var_name: my_entity.property_by_name[var_name] = 2 # also, check if such a property esists if my_entity.property_exists(var_name): # read the value of the Dynamic property whose name is in var_name print my_entity.property_by_name[var_name] Thanks...

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• What is the correct way to customize Icon and Text position of items in a QListView?

  - by petermcg

  I'm using C++ and Qt's (4.6) model/view framework and wondering what is the correct way to change the display of items in a QListView or a class derived from QListView from: to: I'm not concerned about the sort order or Flow, I'm interested in the best way to correctly position the text to the right of the icon. If this can only be done by writing a custom QStyledItemDelegate that's totally fine, I want to rule out whether this is the correct approach or whether it's best to look at setLayout or similar, example code would help. The example application I'm looking at is the 'interview' example from qtdemo which amongst other things displays icons and text in a QListView.

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• New to threading in C#, can you make thread methods generic and what are the dangers?

  - by ibarczewski

  Hey all, I'm just now starting to get into the idea of threading, and wanted to know if I could make this more abstract. Both foo and bar derive methods from a base class, so I'd like to pass in one or the other and be able to do work using a method that was derived. I'd also like to know how you properly name threads and the methods inside threads. if (ChkFoo.Checked) { Thread fooThread = new Thread(new ThreadStart(this.ThreadedFooMethod)); fooThread.Start(); } if (ChkBar.Checked) { Thread barThread = new Thread(new ThreadStart(this.ThreadedBarMethod)); barThread.Start(); } . . . public void ThreadedFooMethod() { Foo newFoo = new Foo(); //Do work on newFoo } public void ThreadedBarMethod() { Bar newBar = new Bar(); //Do similar work } Thanks all!

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• OnClickListener - x,y location of event?

  - by Mark

  Hi, I have a custom view derived from View. I'd like to be notified when the view is clicked, and the x,y location of where the click happened. Same for long-clicks. Looks like to do this, I need to override onTouchEvent(). Is there no way to get the x,y location of the event from an OnClickListener instead though? If not, what's a good way of telling if a motion event is a 'real' click vs a long-click etc? The onTouchEvent generates many events in rapid succession etc. Thanks

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• InvalidCastException: System.Web.UI.PartialCachingControl -> MyCustomControl when OutputCaching

  - by marcinn

  The problem: I am unable to use OutputCaching with my controls which derives from MyCustomControl. Controls are loaded dynamically using definitions from database with Page.LoadControl method. When I add to ascx <%@ OutputCache VaryByParam="*" Duration="3600"% the "InvalidCastException: System.Web.UI.PartialCachingControl - MyCustomControl" exception is thrown. I am unable to modify assembly witch contains dynamic loading controls logic. Is there any way to fix it in derived controls? The second question is about iis7 and native output caching - is it resolves this problem? (I tried to set up several performance counters and I saw that cache wasn't hit...)

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• VB.NET Abstract Property

  - by ElPresidente

  I have an abstract "GridBase" class with two types of derived classes "DetailGrid" and "HeaderGrid". Respectively, one is comprised of "DetailRow" objects and the other "HeaderRow" objects. Both of those inherit from a "RowBase" abstract class. What I am trying to do is the following: Public MustInherit Class GridBase Private pRows As List(Of RowBase) Public ReadOnly Property Rows As List(Of RowBase) Get Return pRows End Get End Property End Class Public Class DetailGrid Inherits GridBase End Class In this scenario, I want DetailGrid.Rows to return a list of DetailRow. I want HeaderRow.Rows to return a list of HeaderRow. Am I on the right track with this or should the Rows property not be included in the GridBase class?

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• GNU General Public License (v2): can a company use the licensed software for free?

  - by EOL

  When a library is released under the GPL v2, can a company use it internally for free? If they develop software based on it, do they have to release it under the GPL, even if they don't distribute it? Can they make money by using (not distributing) internally developed software that links to the GPL'ed library, without any compensation for the author? I am looking for a software license that only allows non-commercial uses (copy, modify, link to); the resulting derived programs must also be free for non-commercial uses. Is there any software license that does this for non-commercial uses, and prevents any commercial use (including using the software in order to make money)? It looks like the Creative Commons licenses are flexible enough to do something close to that, but I've read against using them for software. What do you think?

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• MySQL: Query to obtain recipes using all given ingredients.

  - by John_A

  hi I have the following simplified tables: CREATE TABLE recipe(id int, name varchar(25)); CREATE TABLE ingredient(name varchar(25)); CREATE TABLE uses_ingredient(recipe_id int, name varchar(25)); I want to make a query that returns all id's of recipes that contain both Chicken and Cream. I have tried SELECT recipe_id FROM uses_ingredient INNER JOIN (SELECT * FROM ingredient WHERE name="Chicken" OR name="Cream") USING (name) GROUP BY recipe_id HAVING COUNT(recipe_id) >= (SELECT COUNT(*) FROM theme); which gives me :"ERROR 1248 (42000): Every derived table must have its own alias" and is probably wrong too. Next I tried SELECT recipe_id FROM (SELECT * FROM ingredient WHERE name="Chicken" OR name="Cream") AS t INNER JOIN uses_ingredient USING (name) GROUP BY recipe_id HAVING COUNT(recipe_id)>= (SELECT COUNT(*) FROM t); which gives "ERROR 1146 (42S02): Table 'recipedb.t' doesn't exist" I want to avoid creating temporary tables including using ENGINE=MEMORY.

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• .NET: Get all Outlook calendar items

  - by Qinnie

  How can I get all items from a specific calendar (for a specific date). Lets say for instance that I have a calendar with a recurring item every Monday evening. When I request all items like this: CalendarItems = CalendarFolder.Items; CalendarItems.IncludeRecurrences = true; I only get 1 item... Is there an easy way to get all items (main item + derived items) from a calendar? In my specific situation it can be possible to set a date limit but it would be cool just to get all items (my recurring items are time limited themselves). I'm using the Microsoft Outlook 12 Object library (Microsoft.Office.Interop.Outlook).

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• How can I get Facebook Profile image from email?

  - by Forbini

  There's an outlook plugin called Xobni that has a really cool feature, if a contact has an email address, it will fetch that contact's profile picture and display it. Their FAQ states the following: Xobni sends an encrypted email address to Facebook to retrieve the Facebook profile for the person who is currently being viewed in the Xobni sidebar. Your own Facebook profile is never altered by Xobni, and all Facebook privacy settings are strictly followed when viewing other profiles. I'd like to duplicate this functionality. However, I can't figure out which API call they're using. I'm assuming when they say "encrypted email address" that's laymen's terms for the email hash. Once a username is derived, the graph api looks ideal for actually fetching the image, but I'm having trouble going from email hash to profile ID.

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• Multiple inclusion of header file c++

  - by iSight

  Hi, I have a problem regarding multiple inclusion of header file in C++ code. say for example, i have three class X,Y,Z. X and Y are derived from Base class Z. And i want to create an instance of X in Y. The code will go like this. class Z{some code} class X:public Z{some code};//here #include header of class Z added class Y:public Z //here #include header of class Z added as well as of X class {private: X* mX;//instance of X some code}; So in this multiple definition of all methods of base class arises. how can i cope with this problem

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• [C++] which is better, throw an exception or return nonzero value?

  - by xis19

  While you are doing C++ programming, you have two choices of reporting an error. I suppose many teachers would suggest you throw an exception, which is derived from std::exception. Another way, which might be more "C" style, is to return a non-zero value, as zero is "ERROR_SUCCESS". Definitively, return an exception can provide much more information of the error and recovery; while the code will bloat a little bit, and making exception-safe in your mind is a little difficult for me, at least. Other way like returning something else, will make reporting an error much easier; the defect is that managing recovery will be a possibly big problem. So folks, as good programmers, which would be your preference, not considering your boss' opinion? For me, I would like to return some nonzero values.

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• How to force calling of QWidget::paintEvent() when its hovered by other window?

  - by Pie_Jesu

  Hi there. I have occured a problem: I'm writing a widget, which displays current date's day number. It's like a button, but it's not derived from QPushButton class. Just from QWidget. So I reimplemented enterEvent(), leaveEvent(), mousePressEvent(), mouseReleaseEvent(). I call update() inside these methods and widget has realistic button behavior (paintEvent() is reimplemented too). But when I change system date and hover that widget with other window, my widget doesn't calls paintEvent() and displays old date. Only when I place mouse over it, widget repaints it's contents. I guess there is an option, which paints old contents on hover event to avoid unnecessary paint events. But I need to disable it. Tried to set many attributes (Qt::WidgetAttribute enum). But it doesn't helps. Please, help me (and sorry for my bad english).

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