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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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  • join 03 table in the database codeIgniter

    - by python
    with my table. person_id serial NOT NULL, firstname character varying(30) NOT NULL, lastname character varying(30), email character varying(50), username character varying(20) NOT NULL, "password" character varying(100) NOT NULL, gender character varying(10), dob date, accesslevel smallint NOT NULL, company_id integer NOT NULL,//Reference to table company position_id integer NOT NULL,//Reference to table position company_id serial NOT NULL, company_name character varying(80) NOT NULL, description character varying(255), address character varying(100) NOT NULL, In my controller ........................ // load data $persons = $this->person_model->get_paged_list(10,0); // generate table data $this->load->library('table'); $this->table->set_empty("&nbsp;"); $this->table->set_heading('No', 'FirstName', 'LastName','E-mail','Company''Gender', 'Date of Birth', 'Actions'); foreach ($persons as $person){ $this->table->add_row(++$i, $person->firstname, $person->lastname, $person->email, $person->company_name, //HOW CAN I GOT THE POSITION TITLE ?, strtoupper($person->gender)=='M'? 'Male':'Female', date('d-m-Y',strtotime($person->dob)), } My model <?php class Person_Model extends Model { private $person= 'person'; function Person(){ parent::Model(); } function list_all(){ $this->db->order_by('person_id','asc'); return $this->db->get($person); } function count_all(){ return $this->db->count_all($this->person); } function get_paged_list($limit = 0, $offset = 0) { $this->db->limit($limit, $offset); $this->db->select("person.*, company.company_name as company"); $this->db->from('person'); $this->db->join('company','person.company_id = company.company_id','left'); //MY QUESTION:? CAN I JOIN MORE WITH TABLE POSITION? $query = $this->db->get(); return $query->result(); } function get_by_id($id){ $this->db->where('person_id', $id); return $this->db->get($this->person); } function save($person){ $this->db->insert($this->person, $person); return $this->db->insert_id(); } function update($id, $person){ $this->db->where('person_id', $id); $this->db->update($this->person, $person); } function delete($id){ $this->db->where('person_id', $id); $this->db->delete($this->person); } } ?>

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  • How to refer to enum constants in c# xml docs

    - by Bruno Martinez
    I want to document the default value of an enum typed field: /// <summary> /// The default value is <see cref="Orientation.Horizontal" />. /// </summary> public Orientation BoxOrientation; The compiler warns that it couldn't resolve the reference. Prefixing F: or M: silences the compiler, but E: also does, so I'm unsure what prefix is correct.

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  • Debug the StackOverFlow exception

    - by BDotA
    When I run my C# program it throws an Stack Overflow exception in one of the methods on a DLL that I have a reference to it in my solution. but no debugging info is available to me because it says it is an stack overflow exception and no info is available. what are the next debugging steps that I should follow to understand what is going on and why ? thanks Edit: here is the code that stops at: static public Collection SortCollection(Collection oCollection, string sPropertyName, string sKeyPropertyName) { return SortCollection(oCollection, sPropertyName, sKeyPropertyName); }

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  • Programming Windows Cluster resource DLLs using Delphi

    - by kaeff
    I wonder whether there's a way to program a resource DLL for Windows Clusters in Delphi. I want to write a program that observes cluster state changes. Judging from the MSDN API reference, all relevant functions are located in the ClusAPI.h and ResAPI.h headers, but unfortunately it seems as if they haven't been ported yet and HeaderConv seems to fail on them. Does anyone has experience in doing such a thing?

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  • Biztalk - how do I set up MSMQ load balancing and high availability ?

    - by FullOfQuestions
    Hi, From what I understand, in order to achieve MSMQ load-balancing, one must use a technology such as NLB. And in order to achieve MSMQ high-availability, one must cluster the related Biztalk Host (and hence the underlying servers have to be in a cluster themselves). Yet, according to Microsoft Documentation, NLB and FailOver Clustering technologies are not compatible. See this link for reference: http://support.microsoft.com/kb/235305 Can anyone PLEASE explain to me how MSMQ load-balancing and high-availability can be achieved? thank you in advance, M

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  • How to emulate OOP with C?

    - by Francisco Garcia
    I would like to know which articles or books are good to use OOP concepts in C. I mean things like using function pointers to emulate classes, strict naming conventions to emulate namespaces, and things like that. Also a reference about how to code in C different types of UML diagrams would be great.

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  • Cannot use ternary operator in LINQ query

    - by Nissan Fan
    I can't figure out why I get a Object reference not set to an instance of an object. error if I use a ternary operator in my LINQ query. var courses = from d in somesource orderby d.SourceName, d.SourceType select new { ID = d.InternalCode, Name = string.Format("{0} - {1}{2}", d.InternalCode, d.SourceName, (d.SourceType.Length > 0 ? ", " + d.SourceType : string.Empty)) }; Any thoughts?

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  • sql report link with rs:Command paramaters not opening in JSF page

    - by H3wh0s33ks
    I have a report that we need to link (which we've checked to be working) to in a JSF project, the link looks like the following: http://www.example.com/report/summary&rs:Command=Render However when we try to load the page that links to it we get the following error: The reference to entity "rs:Command" must end with the ';' How can I link to the report within my pages and prevent it from trying to parse the rs:Command?

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  • How can I make a numerical value for a taskbar icon in C#?

    - by Waffles
    I'm trying to find a way to display the current processor time of an application to the user via the taskbar when my application is minimized. For reference, I want something like what is implemented in Coretemp, where if you minimize the application, you can still see the temperature of the computer processor cores in the taskbar. Does anyone know of how this is done in C#?

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  • How to set up an Eclipse P2 server using Google Sites?

    - by PaulB
    I'm trying to use Google Sites to host an Eclipse P2 site. However, Install New Software fails to the site because the features and plugins directories are not found. It seems that Google Sites only simulates subdirectories on FileCabinet pages. Is there an alternative Google Sites approach? Or is there a way to set up a P2 site without subdirectories or so that Install New Software will reference a zip file? Any alternative recommendations?

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  • Best ways to write a method that updates two objects in a multithreaded java environment?

    - by DanielHonig
    Suppose we have a class called AccountService that manages the state of accounts. AccountService is defined as interface AccountService{ public void debit(account); public void credit(account); public void transfer(Account account, Account account1); } Given this definition, what is the best way to implement transfer() so that you can guarantee that transfer is an atomic operation. I'm interested in answers that reference Java 1.4 code as well as answers that might use resources from java.util.concurrent in Java 5

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  • Why do custom styled Google Maps (v3) not support marker animation (pin drop)?

    - by Plum Pie
    For example, I cannot combine the concepts of this simple example: link text with the concepts of this example: link text, which uses the styled V3 api. In Chrome I get an error saying that: Uncaught TypeError: Cannot read property 'DROP' of undefined And it refers to this line of code: animation: google.maps.Animation.DROP, When I replace the javascript link reference to use the version of the API from the first example, the error goes away, but I lose the custom styling. I have not tried this in Firefox or IE. EDIT: Link to example: link text

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  • ASP.NET MVC image upload store location (db vs filesystem)

    - by adrin
    I am writing web application using ASP.NET MVC + NHibernate + Postres stack. I wonder if images uploaded should be stored in database as binary blobs or on filesystem (and reference only in db). One advantage of db storage I can think of is easy backup/recovery of all data without reverting to filesystem copy tools. On the other hand I suspect that filesystem access may be faster (but is it especially when dealing with many concurrent requests?) What are your suggestions?

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  • C++ stream as a parameter when overloading operator<<

    - by TheOm3ga
    I'm trying to write my own logging class and use it as a stream: logger L; L << "whatever" << std::endl; This is the code I started with: #include <iostream> using namespace std; class logger{ public: template <typename T> friend logger& operator <<(logger& log, const T& value); }; template <typename T> logger& operator <<(logger& log, T const & value) { // Here I'd output the values to a file and stdout, etc. cout << value; return log; } int main(int argc, char *argv[]) { logger L; L << "hello" << '\n' ; // This works L << "bye" << "alo" << endl; // This doesn't work return 0; } But I was getting an error when trying to compile, saying that there was no definition for operator<<: pruebaLog.cpp:31: error: no match for ‘operator<<’ in ‘operator<< [with T = char [4]](((logger&)((logger*)operator<< [with T = char [4]](((logger&)(& L)), ((const char (&)[4])"bye")))), ((const char (&)[4])"alo")) << std::endl’ So, I've been trying to overload operator<< to accept this kind of streams, but it's driving me mad. I don't know how to do it. I've been loking at, for instance, the definition of std::endl at the ostream header file and written a function with this header: logger& operator <<(logger& log, const basic_ostream<char,char_traits<char> >& (*s)(basic_ostream<char,char_traits<char> >&)) But no luck. I've tried the same using templates instead of directly using char, and also tried simply using "const ostream& os", and nothing. Another thing that bugs me is that, in the error output, the first argument for operator<< changes, sometimes it's a reference to a pointer, sometimes looks like a double reference...

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  • DirectShowNet for Compact framework licensing?

    - by GameTrainersWTF
    http://directshownetcf.com/ I can't seem to find anything on google to suggest whether or not i can use this in a commercial application. It does reference you can buy the source code for money, but nothing (that i can see) about using the already compiled dll. Has anyone got any information on this?

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  • [self removeFromSuperview] not doing dealloc

    - by jonydep
    i have this in the superview: mySubView = [[MySubView alloc] init]; [self addSubview:mySubView]; [mySubView release]; then at some point later, in the sub view, this: [self removeFromSuperview]; when i debug it, i notice that the dealloc for the subview is never called, even though i'm fairly sure the reference count should be 0. any ideas why this might be? thanks.

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