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• Is it ok to reference .Net assemblies liberally?

  - by panamack

  I'm building a WPF application and working with the MVVM pattern. I have 4 projects in my solution, 3 class libraries, Data, Model and ViewModel and the WPF executable View. Is there anything wrong with the Model referencing WindowsBase so that I can use ObservableCollection<T> for example or can I just make use of what I intuitively feel I need without worrying about the original purposes of the class in the framework e.g. collection databinding.

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• Derived template override return type of member function C++

  - by Ruud v A

  I am writing matrix classes. Take a look at this definition: template <typename T, unsigned int dimension_x, unsigned int dimension_y> class generic_matrix { ... generic_matrix<T, dimension_x - 1, dimension_y - 1> minor(unsigned int x, unsigned int y) const { ... } ... } template <typename T, unsigned int dimension> class generic_square_matrix : public generic_matrix<T, dimension, dimension> { ... generic_square_matrix(const generic_matrix<T, dimension, dimension>& other) { ... } ... void foo(); } The generic_square_matrix class provides additional functions like matrix multiplication. Doing this is no problem: generic_square_matrix<T, 4> m = generic_matrix<T, 4, 4>(); It is possible to assign any square matrix to M, even though the type is not generic_square_matrix, due to the constructor. This is possible because the data does not change across children, only the supported functions. This is also possible: generic_square_matrix<T, 4> m = generic_square_matrix<T, 5>().minor(1,1); Same conversion applies here. But now comes the problem: generic_square_matrix<T, 4>().minor(1,1).foo(); //problem, foo is not in generic_matrix<T, 3, 3> To solve this I would like generic_square_matrix::minor to return a generic_square_matrix instead of a generic_matrix. The only possible way to do this, I think is to use template specialisation. But since a specialisation is basically treated like a separate class, I have to redefine all functions. I cannot call the function of the non-specialised class as you would do with a derived class, so I have to copy the entire function. This is not a very nice generic-programming solution, and a lot of work. C++ almost has a solution for my problem: a virtual function of a derived class, can return a pointer or reference to a different class than the base class returns, if this class is derived from the class that the base class returns. generic_square_matrix is derived from generic_matrix, but the function does not return a pointer nor reference, so this doesn't apply here. Is there a solution to this problem (possibly involving an entirely other structure; my only requirements are that the dimensions are a template parameter and that square matrices can have additional functionality). Thanks in advance, Ruud

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• question about c++ template functions taking any type as long that type meets at least one of the re

  - by smerlin

  Since i cant explain this very well, i will start with a small example right away: template <class T> void Print(const T& t){t.print1();} template <class T> void Print(const T& t){t.print2();} This does not compile: error C2995: 'void Print(const T &)' : function template has already been defined So, how can i create a template function which takes any type T as long as that type has a print1 memberfunction OR a print2 memberfunction (no polymorphism) ?

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• C#: why does the string type have a .ToString() method

  - by Craig Johnston

  C#: Why does the string data type have a .ToString() method?

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• Using block around a static/singleton resource reference

  - by byte

  This is interesting (to me anyway), and I'd like to see if anyone has a good answer and explanation for this behavior. Say you have a singleton database object (or static database object), and you have it stored in a class Foo. public class Foo { public static SqlConnection DBConn = new SqlConnection(ConfigurationManager.ConnectionStrings["BAR"].ConnectionString); } Then, lets say that you are cognizant of the usefulness of calling and disposing your connection (pretend for this example that its a one-time use for purposes of illustration). So you decide to use a 'using' block to take care of the Dispose() call. using (SqlConnection conn = Foo.DBConn) { conn.Open(); using (SqlCommand cmd = new SqlCommand()) { cmd.Connection = conn; cmd.CommandType = System.Data.CommandType.StoredProcedure; cmd.CommandText = "SP_YOUR_PROC"; cmd.ExecuteNonQuery(); } conn.Close(); } This fails, with an error stating that the "ConnectionString property is not initialized". It's not an issue with pulling the connection string from the app.config/web.config. When you investigate in a debug session you see that Foo.DBConn is not null, but contains empty properties. Why is this?

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• C++/CLI, "constant" reference to a tracking handle

  - by liori

  Hello, I have spotted something like this in code: void foo(IList<int>^ const & list ) { ... } What does this ^ const& mean? I looked in the C++/CLI specification, but found no comments on making constant tracking references, nor the ^& combo. Is this legal?

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• Check if a type is an instantiation of a template

  - by Pedro Lacerda

  I have structs like struct RGBA (T) {/* ... */} struct BMPFile (DataT) if (is(DataT == RGBA)) {/* ... */} But is(DataT == RGBA) cannot work because DataT is a type and RGBA is a template. Instead I need check if a type is an instantiation of a template in order to declare file like BMPFile!(RGBA!ushort) file; In a comment @FeepingCreature showed struct RGBA(T) { alias void isRGBAStruct; } struct BMPFile (DataT) if (is(DataT.isRGBAStruct)) {} Although to be working I have no tips on alias void isRGBAStruct.

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• Backbone: Easiest way to maintain reference to 'this' for a Model inside callbacks

  - by Garrett

  var JavascriptHelper = Backbone.Model.extend("JavascriptHelper", {}, // never initialized as an instance { myFn: function() { $('.selector').live('click', function() { this.anotherFn(); // FAIL! }); }, anotherFn: function() { alert('This is never called from myFn()'); } } ); The usual _.bindAll(this, ...) approach won't work here because I am never initializing this model as an instance. Any ideas? Thanks.

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• Cannot implicitly convert type 'char*' to 'bool'

  - by neeraj

  i was trying to passing pointer value in the function , i really got stuck here I am a beginner , not getting what value should be put this is programme from the reference of the book "Cracking the coding interview " By Gayle Laakmann McDowell, class Program { unsafe void reverse(char *str) { char* end = str; char tmp; if (str) //Cannot implicitly convert type 'char*' to 'bool' { while(*end) //Cannot implicitly convert type 'char*' to 'bool' { ++end; } --end; while(str<end) { tmp = *str; *str+= *end; *end-= tmp; } } } public static void Main(string[] args) { } }

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• C# - What is root reference ?

  - by DotNetGuy

  class GCTest { static Object r1; static void Main() { r1 = new Object(); Object r2 = new Object(); Object r3 = new Object(); System.GC.Collect(); // what can be reclaimed here ? r1 = null; r3.ToString(); System.GC.Collect(); // what can be reclaimed here ? } } // code from - DonBox's Essential .Net

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• Is Android reference at android.com good enough

  - by the100rabh

  Hi, I am a C++ developer, but have a fair idea of Java as I learnt it in college 5years ago. I have been trying to learn programming for android. But instead of rushing to buy books, I have tried to read through the Android Dev Guide and learn from there making use of the sample applications. Thats besides SO ofcourse. I am trying to make some apps based on ideas I have. So my question is, Is it suitable or possible to learn android programming this way. Or is there something that I will be missing in all this.

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• Is there a definitive list of uri patterns for use in android apps made by google?

  - by The Trav

  Apart from http://developer.android.com/guide/appendix/g-app-intents.html (which is quite good but fairly limited in the number of apps/uri's it covers) I've been unable to find a decent reference source for looking up URI's to use when integrating with google apps. I'm currently working on triggering the "add new contact" UI, and have found that the tel: uri pattern seems to work, but what if I only have a name and an email? I wouldn't have expected I'd need to rely on sample code / trial and error, but I really can't see anywhere where the intent/URI interface is supposed to be documented in android apps. Does such a standard exist? Is there some quasi standard / user database that I can consult? On a platform with such a good inter-interoperability architecture it just seems like something so useful I can't believe it's not there

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• restrict a character to type in a text box

  - by Arpan

  how we can restrict a character to type in a text box.

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• Iterating over member typed collection fails when using untyped reference to generic object

  - by Alexander Pavlov

  Could someone clarify why iterate1() is not accepted by compiler (Java 1.6)? I do not see why iterate2() and iterate3() are much better. This paragraph is added to avoid silly "Your post does not have much context to explain the code sections; please explain your scenario more clearly." protection. import java.util.Collection; import java.util.HashSet; public class Test<T> { public Collection<String> getCollection() { return new HashSet<String>(); } public void iterate1(Test test) { for (String s : test.getCollection()) { // ... } } public void iterate2(Test test) { Collection<String> c = test.getCollection(); for (String s : c) { // ... } } public void iterate3(Test<?> test) { for (String s : test.getCollection()) { // ... } } } Compiler output: $ javac Test.java Test.java:11: incompatible types found : java.lang.Object required: java.lang.String for (String s : test.getCollection()) { ^ Note: Test.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. 1 error

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• Does "Value Restriction" practically mean that there is no higher order functional programming?

  - by Sadache

  Does "Value Restriction" practically mean that there is no higher order functional programming? I have a problem that each time I try to do a bit of HOP I get caught by a VR error. Example: let simple (s:string)= fun rq->1 let oops= simple "" type 'a SimpleType= F of (int ->'a-> 'a) let get a = F(fun req -> id) let oops2= get "" and I would like to know whether it is a problem of a prticular implementation of VR or it is a general problem that has no solution in a mutable type-infered language that doesn't include mutation in the type system.

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• Linq to SQl Stored Procedure Problem( it can't figure out the return type)

  - by chobo2

  Hi I have this SP USE [Test] GO SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE PROCEDURE [dbo].[UsersInsert](@UpdatedProdData XML) AS INSERT INTO dbo.UserTable(UserId,UserName,LicenseId,Password,PasswordSalt,Email,IsApproved,IsLockedOut,CreateDate, LastLoginDate,LastLockOutDate,FailedPasswordAttempts,RoleId) SELECT @UpdatedProdData.value('(/ArrayOfUsers/Users/UserId)[1]', 'uniqueidentifier'), @UpdatedProdData.value('(/ArrayOfUsers/Users/UserName)[1]', 'varchar(20)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/LicenseId)[1]', 'varchar(50)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/Password)[1]', 'varchar(128)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/PasswordSalt)[1]', 'varchar(128)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/Email)[1]', 'varchar(50)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/IsApproved)[1]', 'bit'), @UpdatedProdData.value('(/ArrayOfUsers/Users/IsLockedOut)[1]', 'bit'), @UpdatedProdData.value('(/ArrayOfUsers/Users/CreateDate)[1]', 'datetime'), @UpdatedProdData.value('(/ArrayOfUsers/Users/LastLoginDate)[1]', 'datetime'), @UpdatedProdData.value('(/ArrayOfUsers/Users/LastLockOutDate)[1]', 'datetime'), @UpdatedProdData.value('(/ArrayOfUsers/Users/FailedPasswordAttempts)[1]', 'int'), @UpdatedProdData.value('(/ArrayOfUsers/Users/RoleId)[1]', 'int') Now this SP creates just fine. It's when I go to VS2010 and try to drag this SP in my method panel of my linq to sql file in design view. It tells me that it can't figure out the return type. I try to go to the properties but it does not have "none" as a choice and I can't type it in. It should be "none" so how do I set it to "none"?

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• Is there a way to localize input type="date" in HTML5

  - by lambacck

  I know that at the time of this writing only Opera supports a browser UI for <input type="date" name="mydate"> and maybe my attempts to localize this field have been met with frustration because niceties like localization have not yet been included in their implementation, but I don't even see mention of it in the HTML5 spec. Is there a way that localization should be specified? Should I do lang="fr" on a parent element? Some notes on the implementation of the site in question: Localization (language) is explicitly picked by the user because they are managing data in multiple languages and it is not reasonable to expect that the user's browser chrome is in the language being viewed or that the browser is providing desired language request headers. I want to be sure that if the page is rendered in French that the date picker provided by browser chrome shows options that make sense for French language. The plan is to fall back to jQueryUI for browsers that do not support type="date", I will use the detection mechanism provided in Dive into HTML 5

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• Redeclaration of parameters

  - by Scott

  While looking through the Selenium source code I noticed the following in the PageFactory: public static <T> T initElements(WebDriver driver, Class<T> pageClassToProxy) { T page = instantiatePage(driver, pageClassToProxy); initElements(driver, page); return page; } public static void initElements(WebDriver driver, Object page) { final WebDriver driverRef = driver; initElements(new DefaultElementLocatorFactory(driverRef), page); } What is the benefit of having the following line? final WebDriver driverRef = driver; Wouldn't it have made sense to just make the parameter final, and then passing that along to the next method without declaring the new reference?

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• GIT core.editor setup on windows along w application PATH reference

  - by delinquentme

  Hey all so i wehnt ahead and opened up my .gitconfig file and manually input the [core] editor = 'C:/Program Files/Notepad++/notepad++.exe' which would allow me to execute command: (im trying to setup my .gitignore list) "C:/Program Files/Notepad++/notepad++.exe" .gitignore im JUSt not interested in typing this out every time that i need to make a file SO ive heard something about editing PATH to allow me to replace the above with something like: npp .gitignore any help would be aprpeciated!

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• Django admin, filter objects by ManyToMany reference

  - by Nick Z

  Hello! There's photologue application, simple photo gallery for django, implementing Photo and Gallery objects. Gallery object has ManyToMany field, which references Photo objects. I need to be able to get list of all Photos for a given Gallery. Is it possible to add Gallery filter to Photo's admin page? If it's possible, how to do it best?

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• Using module include in OCaml

  - by Geoff

  In OCaml 3.11, I want to "extend" an existing module using the include directive, like so: module MyString = struct include String let trim s = ... end No problem. But now I want to expose this module's type explicitly (i.e. in a .mli file). I want something like this: module MyString : sig include String val trim : string -> string end But the include syntax is not correct because String refers to a module, not a module type (and the compiler does indeed barf). How can I refer to the module type for String here (without having write it out explicitly in a sig expression)? Thanks!

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• Null reference for first memory address between 0 - 65535

  - by Terry

  I would like to understand a bit more about memory and I was unable to find it from Google, please forgive me if this is silly question. How come the following code, accessing memory address 0(and up to 65535) in C# would throw NullReferenceException byte* pointer = (byte*)0; byte test = *pointer; Thanks a lot in advance!

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• Using NSArray for C-type int comparisons

  - by Andrew Barinov

  I would like to iterate through an NSArray of ints and compare each one to a specific int. All ints are C type ints. The code I am using is as follows: -(int)ladderCalc: (NSArray*)amounts: (int)amount { int result; for (NSUInteger i=0; i< [amounts count]; i++) { if (amount < [amounts objectAtIndex:i]); { // do something } // do something } } However I get an error when comparing the int amount to the result of [amounts objectAtIndex:i] because you cannot compare id to int. Why is the id involved in this case? Shouldn't objectAtIndex just return the object at the index specified? Is it possible to cast the object returned to an C int and then do the comparison? Or should I just dispense with NSArray and do this type of thing in C?

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• Referencing text input fields in CKEditor dialogs

  - by rt-uk

  Hi, I've been playing around with this for a couple of weeks now with no success... In a CKEditor dialog, text input fields are renamed with a unique number - e.g. id: 'txtUrl' will become something like id='27_textinput'. How do I reference this? // I feel it should be something like: var myfield = CKEDITOR.instances.myElement.document.$.body.getId('txtUrl'); // or maybe: var myfield = CKEDITOR.dialog.getContentElement('info','txtUrl'); // and then: myfield.value = 'myvalue'; But these don't work. Please help! Thanks in advance, R

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• Problem when trying to define Show for my Point3D type in Haskell

  - by devoured elysium

  I am trying to define Show for my Point3D type: type Point3D = (Integer, Integer, Integer) instance Show Point3D where show (x,y,z) = "<" ++ (show x) ++ "," ++ (show y) ++ "," ++ (show z) ++ ">" yet I must be missing something in the sintax, as I am always getting an error: Illegal instance declaration for `Show Point3D' (All instance types must be of the form (T t1 ... tn) where T is not a synonym. Use -XTypeSynonymInstances if you want to disable this.) In the instance declaration for `Show Point3D' What am I doing wrong?

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