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  • How to pass a class method as an argument for another function in C++ and openGL?

    - by tsubasa
    I know this thing works: void myDisplay() { ... } int main() { ... glutDisplayFunc(myDisplay) ... } so I tried to include myDisplay() function to a class that I made. Because I want to overload it in the future with a different class. However, the compiler complains that argument of type 'void (ClassBlah::)()' does not match 'void(*)()' . Here is the what I try to make: class ClassBlah { .... void myDisplay() .... } ...... int main() { ... ClassBlah blah glutDisplayFunc(blah.myDisplay) ... } Does anybody knows how to fix this problem? Many thanks.

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  • Should this work?

    - by Noah Roberts
    I am trying to specialize a metafunction upon a type that has a function pointer as one of its parameters. The code compiles just fine but it will simply not match the type. #include <iostream> #include <boost/mpl/bool.hpp> #include <boost/mpl/identity.hpp> template < typename CONT, typename NAME, typename TYPE, TYPE (CONT::*getter)() const, void (CONT::*setter)(TYPE const&) > struct metafield_fun {}; struct test_field {}; struct test { int testing() const { return 5; } void testing(int const&) {} }; template < typename T > struct field_writable : boost::mpl::identity<T> {}; template < typename CONT, typename NAME, typename TYPE, TYPE (CONT::*getter)() const > struct field_writable< metafield_fun<CONT,NAME,TYPE,getter,0> > : boost::mpl::false_ {}; typedef metafield_fun<test, test_field, int, &test::testing, 0> unwritable; int main() { std::cout << typeid(field_writable<unwritable>::type).name() << std::endl; std::cin.get(); } Output is always the type passed in, never bool_.

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  • How to properly assign a value to the member of a struct that has a class data type?

    - by sasayins
    Hi, Please kindly see below for the codes. Its compiling successfully but the expected result is not working. Im very confused because my initialization of the array is valid, //cbar.h class CBar { public: class CFoo { public: CFoo( int v ) : m_val = v {} int GetVal() { return m_val; } private: int m_val; }; public: static const CFoo foo1; static const CFoo foo2; public: CBar( CFoo foo ) m_barval( foo.GetVal() ){} int GetFooVal() { return m_barval; } private: int m_barval; }; //cbar.cpp const CBar::CFoo foo1 = CBar::CFoo(2); const CBar::CFoo foo2 = CBar::CFoo(3); //main.cpp struct St { CBar::CFoo foo; }; St st[] = { CBar::foo1, CBar::foo2 }; for( int i=0; i<sizeof(st)/sizeof(St); i++ ) { CBar cbar( st[i].foo ); std::cout << cbar.GetFooVal() << std::endl; } But then when I change the St::foo to a pointer. And like assign the address of CBar::foo1 or CBar::foo2, its working, like this, //main.cpp struct St { const CBar::CFoo *foo; }; St st[] = { &CBar::foo1, &CBar::foo2 }; for( int i=0; i<sizeof(st)/sizeof(St); i++ ) { CBar cbar( *st[i].foo ); std::cout << cbar.GetFooVal() << std::endl; } The real problem is. The app should output 2 3 Please advice. Many thanks.

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  • Class<T> and static method Class.forName() drive me crazy.

    - by matt
    Hi, this code doesn't compile. I'm wondering what I am doing wrong: private static Importable getRightInstance(String s) throws Exception { Class<Importable> c = Class.forName(s); Importable i = c.newInstance(); return i; } where Importable is an interface and the string s is the name of an implementing class. The compiler says: ./Importer.java:33: incompatible types found : java.lang.Class<capture#964 of ?> required: java.lang.Class<Importable> Class<Importable> c = Class.forName(format(s)); thanks for any help! All the solutions Class<? extends Importable> c = Class.forName(s).asSubclass(Importable.class); and Class<? extends Importable> c = (Class<? extends Importable>) Class.forName(s); and Class<?> c = Class.forName(format(s)); Importable i = (Importable)c.newInstance(); give this error: Exception in thread "main" java.lang.IncompatibleClassChangeError: class C1 has interface Importable as super class where C1 is effectively a class implementing Importable, one of those i want to cast to Importable.

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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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  • Proper method to detect device model (iPhone/iPod Touch)?

    - by Mark
    Is this the proper way to detect which device a user is running? NSString *currentModel = [[UIDevice currentDevice] model]; if ([currentModel isEqualToString:@"iPhone"]) { // The user is running on iPhone so allow Call, Camera, etc. } else { // The user is running on a different device (iPod / iPad / iPhone Simulator) disallow Call. }

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  • How to stable_sort without copying?

    - by Mehrdad
    Why does stable_sort need a copy constructor? (swap should suffice, right?) Or rather, how do I stable_sort a range without copying any elements? #include <algorithm> class Person { Person(Person const &); // Disable copying public: Person() : age(0) { } int age; void swap(Person &other) { using std::swap; swap(this->age, other.age); } friend void swap(Person &a, Person &b) { a.swap(b); } bool operator <(Person const &other) const { return this->age < other.age; } }; int main() { static size_t const n = 10; Person people[n]; std::stable_sort(people, people + n); }

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  • Python: Calling method A from class A within class B?

    - by Tommo
    There are a number of questions that are similar to this, but none of the answers hits the spot - so please bear with me. I am trying my hardest to learn OOP using Python, but i keep running into errors (like this one) which just make me think this is all pointless and it would be easier to just use methods. Here is my code: class TheGUI(wx.Frame): def __init__(self, title, size): wx.Frame.__init__(self, None, 1, title, size=size) # The GUI is made ... textbox.TextCtrl(panel1, 1, pos=(67,7), size=(150, 20)) button1.Bind(wx.EVT_BUTTON, self.button1Click) self.Show(True) def button1Click(self, event): #It needs to do the LoadThread function! class WebParser: def LoadThread(self, thread_id): #It needs to get the contents of textbox! TheGUI = TheGUI("Text RPG", (500,500)) TheParser = WebParser TheApp.MainLoop() So the problem i am having is that the GUI class needs to use a function that is in the WebParser class, and the WebParser class needs to get text from a textbox that exists in the GUI class. I know i could do this by passing the objects around as parameters, but that seems utterly pointless, there must be a more logical way to do this that doesn't using classes seem so pointless? Thanks in advance!

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  • method for creating PHP templates (ie html with variables)?

    - by Haroldo
    I'm designing my html emails, these are to be a block of html containing variables that i can store in a $template variable. My problem comes with the storing in the variable part. putting all my html into php makes it a pain in the bum to work with. for example, the below code is fine for a simple email but once i start getting nested tables etc its going to get really confusing... $template.= 'Welcome ' . $username . '<br /><br /><br />'; $template.= 'Thank-you for creating an account <br /><br />'; $template.= 'Please confirm your account by click the link below! <br /><br />'; $template.= '<a href="' . $sitepath . '?email=' . $email . '&conf_key=' . $key . '" style="color: #03110A;"><font size="5" font-family="Verdana, Geneva, sans-serif" color="#03110A">' . $key . '</font></a>'; $template.='</body></html>'; is there a way i can still store the html in a $var but not have to write it like this?

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  • How to add a method to an existing class in PHP?

    - by sombe
    I'm using WordPress as a CMS, and I want to extend one of its classes without having to inherit from another class; i.e. I simply want to "add" more methods to that class: class A { function do_a() { echo 'a'; } } then: function insert_this_function_into_class_A() { echo 'b'; } (some way of inserting the latter into A class) and: A::insert_this_function_into_class_A(); # b Is this even possible in tenacious PHP?

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  • Need method to seek next/previous records id without cycling through all records.

    - by dqhendricks
    I am using MySQL and PHP. I have a MySQL blog post result set with id fields, and publish_date fields. I display one blog post per page, and the script knows which blog post to display based on $_GET['id'], which correlates to each blog entry's id field. I would like to reference them by id in the url, because I would like each blog post to have a perminant url. I would like to order the blog posts by publish date (descending). Now, on each page there will be next and previous links, which contain the $_GET['id'] value for the next and previous blog posts. How can I figure out what the id of the next and previous blog posts (determined by it's publish_date order) without cycling through each mysql result row? I can't mysql_data_seek(), because I do not know the row index of the current blog post id. I do not want to store a row index in a GET variable because the urls would no longer be perminant. I obviously cannot store the row index in a SESSION variable because then direct links to specific blog posts would have broken next and previous links. Any suggestions would be greatly appreciated.

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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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  • Circular increment: Which is "better"?

    - by Helper Method
    When you have a circular buffer represented as an array, and you need the index to wraparound (i.e., when you reach the highest possible index and increment it), is it "better" to: return (i++ == buffer.length) ? 0: i; Or return i++ % buffer.length; Has using the modulo operator any drawbacks? Is it less readable than the first solution?

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