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• Using C++ is a Linked-List implementation without using pointers possible or not?

  - by sonicoder

  My question is very simply, can one using C++, implment a link-list data structure without using pointers (next nodes)? To further qualify my question, I'm mean can one create a Linked-List data structure using only class instantiations. A common node definition might be like so: template<typename T> struct node { T t; node<T>* next; node<T>* prev; }; I'm aware of std::list etc, I'm just curious to know if its possible or not - and if so how? code examples will be greatly appreciated.

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• Iterator in Java.

  - by theband

  What is Iterator and collections? Does these two have any relations? // the interface definition Interface Iterator { boolean hasNext(); Object next(); // note "one-way" traffic void remove(); } // an example public static void main (String[] args){ ArrayList cars = new ArrayList(); for (int i = 0; i < 12; i++) cars.add (new Car()); Iterator it = cats.iterator(); while (it.hasNext()) System.out.println ((Car)it.next()); } Does the Interface Iterator has these method names alone predefined or its user defined?. What does these four lines below actually tell? cars.add (new Car()); Iterator it = cats.iterator(); while (it.hasNext()) System.out.println ((Car)it.next()); Thanks i am going through a book in collections.

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• [C#] How to create a constructor of a class that return a collection of instances of that class?

  - by codemonkie

  My program has the following class definition: public sealed class Subscriber { private subscription; public Subscriber(int id) { using (DataContext dc = new DataContext()) { this.subscription = dc._GetSubscription(id).SingleOrDefault(); } } } ,where _GetSubscription() is a sproc which returns a value of type ISingleResult<_GetSubscriptionResult> Say, I have a list of type List<int> full of 1000 ids and I want to create a collection of subscribers of type List<Subscriber>. How can I do that without calling the constructor in a loop for 1000 times? Since I am trying to avoid switching the DataContext on/off so frequently that may stress the database. TIA.

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• Return Integer value from SSIS execute SQL Task

  - by Bokhari

  I am using SQL Server 2005 Business Intelligence Studio and struggling with returning an integer value from a very simple execute SQL Task. For a very simple test, I wrote the SQL Statement as: Select 35 As 'TotalRecords' Then, I specified ResultSet as ResultName = TotalRecords and VariableName = User::TotalRecords When I execute this, the statement is executed but the variable doesn't have the updated value. However, it has the default value that I specified while variable definition. The return of a date variable works, but integer variable isn't working. The type of User::TotalRecords specified is Int32 in a package scope. Thanks for any hints

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• InfoPath Getting SharePoint Group Information

  - by anon

  I have an InfoPath form embedded in an aspx page on a SharePoint site. How do I bind the SharePoint user groups to a drop-down list on my form? What I've tried so far is to create a data connection to a web service (method GetGroupCollectionFromWeb) to pull the data. Next, I open the list box properties, select "Look up values from an external data source", select the data source, assign the entries, and I get the following error: "You must select a repeating group or field." What I don't understand is that since the method I am calling is called GetGroupCollectionFromWeb, isn't the return value a collection? And aren't collections repeating by definition? What am I missing, and is there a workaround? Thank you.

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• Is there a .def file equicalent on Linux for controlling exported function names in a shared library

  - by morpheous

  I am building a shared library on Ubuntu 9.10. I want to export only a subset of my functions from the library. On the Windows platform, this would be done using a module definition ( .def) file which would contain a list of the external and internal names of the functions exported from the library. I have the following questions: How can I restrict the exported functions of a shared library to those I want (i.e. a .def file equivalent) Using .def files as an example, you can give a function an external name that is different from its internal name (useful for prevent name collisions and also redecorating mangled names etc) On windows I can use the EXPORT command (IIRC) to check the list of exported functions and addresses, what is the equivalent way to do this on Linux?

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• Beginner questions regarding Python classes.

  - by Andy

  Hi. I am new to Python so please don't flame me if I ask something too noobish :) 1. Consider I have a class: class Test: def __init__(self, x, y): self.x = x self.y = y def wow(): print 5 * 5 Now I try to create an object of the class: x = Test(3, 4) This works as expected. However, when I try to call the method wow(), it returns an error, which is fixed by changing wow() to: def wow(self) Why do I need to include self and if I don't, what does the method mean?2. In the definition of __init__: def __init__(self, x, y): self.x = x self.y = y Why do I need to declare x and y, when I can do this: def __init__(self): self.x = x self.y = y I hope I am being clear... Thanks for your time.

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• .Net Template Engine/Report Solution

  - by runxc1 Bret Ferrier

  I am looking to add custom reports/forms to a web application. I want users to be able to upload a report definition/template file and then be able to print out a PDF or word document (one or the other it doesn't need to be both) for each of their widgets based off of the template they uploaded. I can't install anything on the server and am looking for an open source/free solution. Data Source- The data will be in the form of a datatable or dataset that the application fetches itself. The report tool does will not be able to connect to any database.

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• Generating a set of files containing dumps of individual tables in a way that guarantees database co

  - by intuited

  I'd like to dump a MySQL database in such a way that a file is created for the definition of each table, and another file is created for the data in each table. I'd like this to be done in a way that guarantees database integrity by locking the entire database for the duration of the dump. What is the best way to do this? Similarly, what's the best way to lock the database while restoring a set of these dump files? edit I can't assume that mysql will have permission to write to files.

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• extending spring form tag library attributes

  - by TimmyJ

  I'm using Spring's form tag library in a Spring MVC application that I am developing. The company I am working for has implemented some company-wide policies based on the definition of custom attributes for certain tags. For instance, by default (though the inclusion of a standard javascript file) all tags have their values automatically converted to upper case. In order to disable this one would define their tag with a custom attribute in the following way: <input type="text" uppercase="false" /> The problem is that the addition of these custom attributes to a spring:form tag causes an error at runtime. I've pasted the error below. org.apache.jasper.JasperException: /WEB-INF/jsp/reportCriteria.jsp(45,5) Attribute uppercase invalid for tag input according to TLD My question is: is there any way to extend the TLD to allow for these attributes, or is there any other way add these custom attributes to these spring:form tags?

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• Why exactly is calling the destructor for the second time undefined behavior in C++?

  - by sharptooth

  As mentioned in this answer simply calling the destructor for the second time is already undefined behavior 12.4/14(3.8). For example: class Class { public: ~Class() {} }; // somewhere in code: { Class* object = new Class(); object->~Class(); delete object; // UB because at this point the destructor call is attempted again } In this example the class is designed in such a way that the destructor could be called multiple times - no things like double-deletion can happen. The memory is still allocated at the point where delete is called - the first destructor call doesn't call the ::operator delete() to release memory. For example, in Visual C++ 9 the above code looks working. Even C++ definition of UB doesn't directly prohibit things qualified as UB from working. So for the code above to break some implementation and/or platform specifics are required. Why exactly would the above code break and under what conditions?

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• Listing C/C++ functions (Code analysis in Unix)

  - by Jond

  Whether we're maintaining unfamiliar code or checking out the implementation details of an Apache module it can help if we can quickly traverse the code and build up an overview of what we're looking at. Grep serves most of my daily needs but there are some cases where it just wont do. Here's a common example of how it can help. To find the definition of a PHP function I'm interested in I can type this at the command line: grep -r "function myfunc" . This could be adapted very quickly to C or C++ if we know the return type, but things become more complicated if, say, I want to list every method that my class provides: grep "function " ./src/mine.class.php Since there's no single keyword that denotes a function or method in C++ and because it's generally more complex syntax, I think I'd need some kind of static code analysis tool, smart use of the C Preprocessor or blind faith the coder followed strict code guidelines (# of whitespace, position of curlies etc) to get these sorts of results. What would you recommend? p.s. be nice, this is my first post ;-) :p

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• Mongoose Not Creating Indexes

  - by wintzer

  I have been trying all afternoon to get my node.js application to create MongoDB indexes properly. I am using the Mongoose ODM and in my schema definition below I have the username field set to a unique index. The collection and document all get created properly, it's just the indexes that aren't working. All the documentation says that the ensureIndex command should be run at startup to create any indexes, but none are being made. I'm using MongoLab for hosting if that matters. I have also repeatedly dropped the collection. Please tell me what I'm doing wrong. var schemaUser = new mongoose.Schema({ username: {type: String, index: { unique: true }, required: true}, hash: String, created: {type: Date, default: Date.now} }, { collection:'Users' }); var User = mongoose.model('Users', schemaUser); var newUser = new Users({username:'wintzer'}) newUser.save(function(err) { if (err) console.log(err); });

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• bash: How to evaluate PS1, PS2, ...?

  - by Harry

  Is there any way to 'evaluate' PS1, PS2, etc from within a bash script? Although, I can use alternate means to get all elements of my current PS1, I would really like to be able to reuse its definition instead of using these alternate means. For example, ===================================== PS1 element --> Alternate means ===================================== \u --> $USER \h --> $HOSTNAME \w --> $PWD ... ===================================== I could very well use the 'alternate means' column in my script, but I don't want to. In my PS1, I, for example, use bold blue color via terminal escape sequences which I'd like to be able to simply reuse by evaluating PS1.

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• Would this union work if char had stricter alignment requirements than int?

  - by paxdiablo

  Recently I came across the following snippet, which is an attempt to ensure all bytes of i (nad no more) are accessible as individual elements of c: union { int i; char c[sizeof(int)]; }; Now this seems a good idea, but I wonder if the standard allows for the case where the alignment requirements for char are more restrictive than that for int. In other words, is it possible to have a four-byte int which is required to be aligned on a four-byte boundary with a one-byte char (it is one byte, by definition, see below) required to be aligned on a sixteen-byte boundary? And would this stuff up the use of the union above? Two things to note. I'm talking specifically about what the standard allows here, not what a sane implementor/architecture would provide. I'm using the term "byte" in the ISO C sense, where it's the width of a char, not necessarily 8 bits.

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• How is inheritance implemented at the memory level?

  - by cambr

  Suppose I have class A { public: void print(){cout<<"A"; }}; class B: public A { public: void print(){cout<<"B"; }}; class C: public C { }; How is inheritance implemented at the memory level? Does C copy print() code to itself or does it have a pointer to the it that points somewhere in A part of the code? How does the same thing happen when we override the previous definition, for example in B (at the memory level)?

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• Use C function in C++ program; "multiply-defined" error

  - by eom

  I am trying to use this code for the Porter stemming algorithm in a C++ program I've already written. I followed the instructions near the end of the file for using the code as a separate module. I created a file, stem.c, that ends after the definition and has extern int stem(char * p, int i, int j) ... It worked fine in Xcode but it does not work for me on Unix with gcc 4.1.1--strange because usually I have no problem moving between the two. I get the error ld: fatal: symbol `stem(char*, int, int)' is multiply-defined: (file /var/tmp//ccrWWlnb.o type=FUNC; file /var/tmp//cc6rUXka.o type=FUNC); ld: fatal: File processing errors. No output written to cluster I've looked online and it seems like there are many things I could have wrong, but I'm not sure what combination of a header file, extern "C", etc. would work.

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• Manage build target variables in iphone project

  - by DougW

  We're transitioning to an automated build process for our iphone projects. These projects can be checked out by individual devs, in which case all the API URLs need to point to a certain path. There are also a variety of build environments, each with their own API root paths. I could probably add multiple, different build targets, and have each of them include a different URLs definition file, but this seems like a lot of upkeep and a bit overkill. Any best practices out there for swapping a few environmental variables for different build environments without much fuss?

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• C# == operator in Immediate window behaves differently than at run-time

  - by Damiano

  Try the following in the Immediate window: object a1 = "a"; object a2 = "a"; a1==a2 // outputs false and you'll see that a1 == a2 outputs false. However, at runtime in either a window app or console, you'll get true: object t1 = "a"; object t2 = "a"; MessageBox.Show((t1 == t2).ToString()); // outputs true The runtime behavior is consistent with the definition for the == operator and strings. Does anybody know if this a bug in the Immediate window?

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• How does one refer to the game1 class's variables in XNA

  - by user1149068

  I try to refer to an array in the Game1 class by creating an object of the Game1 class with its definition Game1 gameObject; , its declaration gameObject = new Game1(); in the constructor, and its usage gameObject.tileArray[xInt, yInt].treed = true;. The game1 class itself remains unchanged in its class code other than some methods and variables. When I try to use this code in the TreeRegion class it gives me "Object reference not set to an instance of an object," leading me to believe that the game1 class is null somehow. How might one change the class or object in order to refer to game1's variables? Mind you I am self-taught and still rather new to C#. The class that refers to game1: http://pastebin.com/0chEcKfq Game1 itself http://pastebin.com/zLDVzCca

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• Why can I create a table with PRIMARY KEY on a nullable column?

  - by AlexKuznetsov

  The following code creates a table without raising any errors: CREATE TABLE test( ID INTEGER NULL, CONSTRAINT PK_test PRIMARY KEY(ID) ) Note that I cannot insert a NULL, as expected: INSERT INTO test VALUES(1),(NULL) ERROR: null value in column "id" violates not-null constraint DETAIL: Failing row contains (null). ********** Error ********** ERROR: null value in column "id" violates not-null constraint SQL state: 23502 Detail: Failing row contains (null). Why can I create a table with a self-contradictory definition? ID column is explicitly declared as NULLable, and it is implicitly not nullable, as a part of the PRIMARY KEY. Does it make sense? Edit: would it not be better if this self-contradictory CREATE TABLE just failed right there?

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• Will Visual Studio 2010 support HTML 5?

  - by Chris

  Since Visual Studio 2010 is slated for release in March of 2010 and HTML 5 is now starting to be used even more widely, I would like to know if Visual Studio will ship with HTML 5 templates, standard controls and support for the more common markup? A definition for support of HTML 5 would be that any new version of Visual Studio should have similar support for code-completion, validation and markup that is currently supported for HTML 4.01 and XHTML 1.0 and 1.1. Update From the Visual Web Develolper Team Blog: HTML 5 intellisense and validation schema for Visual Studio 2008 and Visual Web Developer is for downloading. Follow the instructions posted on the page to install the new scheme. Seems like the Visual Studio Team will be supporting HTML 5 after all.

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• Unable to type cast <AnonymousType#1> to <WindowsFormsApplication1.Attributes> [ C#3.0 ]

  - by Newbie

  I have List<Attributes> la = new List<Attributes>(); la = (from t in result let t1 = t.AttributeCollection from t2 in t1 where t2.AttributeCode.Equals(attributeType) let t3 = t2.TimeSeriesData from k in t3.ToList() where k.Key.Equals(startDate) && k.Key.Equals(endDate) select new { AttributeCode = attributeType, TimeSeriesData = fn(k.Key, k.Value.ToString()) }).ToList<Attributes>(); I am getting the error: 'System.Collections.Generic.IEnumerable<AnonymousType#1>' does not contain a definition for 'ToList' and the best extension method overload 'System.Linq.Enumerable.ToList<TSource>(System.Collections.Generic.IEnumerable<TSource>)' has some invalid arguments I understood tye error meaning but how to type cast it. I have used var and then iterating over it got the result. But without that any other way by which I can do it? Using C# 3.0 Thanks

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• Objective C instance variables - Newbie

  - by Dwayne King

  OK - so I'm sure my confusion here is just a result of being stuck in a "Java mindset" and not understanding how Obj C differs in this case. In Java, I can declare a variable in a class, like this, and each instance of that class will have it's own: MyClass { String myVar; MyClass() { // constructor } } In Obj C I tried to do the same thing by declaring a variable only in the .m file like this: #import "MyClass.h" @implementation MyClass NSString *testVar; @end My expectation here was that this variable has a scope limited to this class. So I created a second class (identical): #import "MySecondClass.h" @implementation MySecondClass NSString *testVar; @end What I'm seeing (and has me baffled) is that changing the variable in one class, affects the value seen in the other class. In fact, if I set a breakpoint, and then "Jump to Definition" of the variable, it takes me to th I've created an extremely small XCode project that demonstrates the problem here Nothing more humbling than moving to a new language :) Thanks in advance.

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• pass parameter from controller to models condition

  - by Alex

  I'm trying to bind a param to a join via a named scope., but I'm getting an error. What is the correct way to do that? has_one :has_voted, :class_name => 'Vote', :conditions => ['ip = :userIp'] # named scopes scope :with_vote, lambda {|ip| { :include => [:has_voted], # like this ?? :conditions => [:has_voted => {:conditions => {:userIp => ip}} ] }} Idea.with_vote(request.ip).all I believe I need the condition definition in the model for it to appear in the ON clause of a JOIN, rather then in the WHERE one. Edit I'm trying to get the following query select Ideas.*, Votes.* from Ideas left outer join Votes on Votes.Idea_id = Idea.id AND Votes.ip = {request.ip}

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