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  • c++/boost: use tuple ctors when subclassing

    - by bbb
    Hi there, is there some way to use a boost tuple's ctors as an addition to the subclass methods (and ctors) like here? // typedef boost::tuple<int, SomeId, SomeStatus> Conn; // Conn(1); // works and initializes using default ctors of Some* struct Conn : boost::tuple<int, AsynchId, AccDevRetStatus> {}; Conn(1); // "no matching function call" (but i want it so much) T.H.X.

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  • How to print structures in PLT Scheme so as to display their fields?

    - by tkf
    I would like code like this: (define-struct thing (a b c)) (define th (make-thing 1 2 3)) to print something like this: (make-thing 1 2 3) when I type "th" into either the DrScheme or MzScheme repl. I am using the language "pretty big" in DrScheme with output style set to "constructor". This is what I get in DrScheme: (make-thing ...) (i literally get the three dots) In MzScheme: #<thing>

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  • get the current time in C

    - by Antrromet
    I want to get the current time of my system. For that i'm using the following code in C. time_t now; struct tm *mytime = localtime(&now); if ( strftime(buffer, sizeof buffer, "%X", mytime) ) { printf("time1 = \"%s\"\n", buffer); } But the problem of this code is that its giving some random time.Also the random time is different all the time.I want the current time of my system. Can anyone please tell me how to solve this issue?

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  • Iterating through boost ptr_vector

    - by Ockonal
    Hello, I have a ptr_vector list of my own objects. Something like this: boost::ptr_vector<SomeClass> *list; list.push_back(new SomeClass()>; ... BOOST_FOREACH(SomeClass *tempObj, list) // [x] { tempObj->... } >‘boost::ptr_vector<SomeClass>*’ is not a class, struct, or union type

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  • template; Point<2, double>; Point<3, double>

    - by Oops
    Hi, I want to create my own Point struct it is only for purposes of learning C++. I have the following code: template <int dims, typename T> struct Point { T X[dims]; Point(){} Point( T X0, T X1 ) { X[0] = X0; X[1] = X1; } Point( T X0, T X1, T X2 ) { X[0] = X0; X[1] = X1; X[2] = X2; } Point<dims, int> toint() { //how to distinguish between 2D and 3D ??? Point<dims, int> ret = Point<dims, int>( (int)X[0], (int)X[1]); return ret; } std::string str(){ //how to distinguish between 2D and 3D ??? std::stringstream s; s << "{ X0: " << X[0] << " | X1: " << X[1] << " }"; return s.str(); } }; int main(void) { Point<2, double> p2d = Point<2, double>( 12.3, 45.6 ); Point<3, double> p3d = Point<3, double>( 12.3, 45.6, 78.9 ); Point<2, int> p2i = p2d.toint(); //OK Point<3, int> p3i = p3d.toint(); //m??? std::cout << p2d.str() << std::endl; //OK std::cout << p3d.str() << std::endl; //m??? std::cout << p2i.str() << std::endl; //m??? std::cout << p3i.str() << std::endl; //m??? char c; std::cin >> c; return 0; } of couse until now the output is not what I want. my questions is: how to take care of the dimensions of the Point (2D or 3D) in member functions of the Point? many thanks in advance Oops

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  • how to identify process in kernel read func without using current->pid

    - by yoavstr
    my lecture wants us to build module where we need to identify each read process and where the same read process called twice on the same writer massage we should insert him to an queue who's we wake up when all readers have read I achieved this goal by by using list of pid's and boolean read/not_read inside each node but he decided to be nasty and require us to it with some argument from FILE struct can you please help me ?....

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  • Template class + virtual function = must implement?

    - by sold
    This code: template <typename T> struct A { T t; void DoSomething() { t.SomeFunction(); } }; struct B { }; A<B> a; is easily compiled without any complaints, as long as I never call a.DoSomething(). However, if I define DoSomething as a virtual function, I will get a compile error saying that B doesn't declare SomeFunction. I can somewhat see why it happens (DoSomething should now have an entry in the vtable), but I can't help feeling that it's not really obligated. Plus it sucks. Is there any way to overcome this? EDIT 2: Okay. I hope this time it makes sence: Let's say I am doing intrusive ref count, so all entities must inherit from base class Object. How can I suuport primitive types too? I can define: template <typename T> class Primitive : public Object { T value; public: Primitive(const T &value=T()); operator T() const; Primitive<T> &operator =(const T &value); Primitive<T> &operator +=(const T &value); Primitive<T> &operator %=(const T &value); // And so on... }; so I can use Primitive<int>, Primitive<char>... But how about Primitive<float>? It seems like a problem, because floats don't have a %= operator. But actually, it isn't, since I'll never call operator %= on Primitive<float>. That's one of the deliberate features of templates. If, for some reason, I would define operator %= as virtual. Or, if i'll pre-export Primitive<float> from a dll to avoid link errors, the compiler will complain even if I never call operator %= on a Primitive<float>. If it would just have fill in a dummy value for operator %= in Primitive<float>'s vtable (that raises an exception?), everything would have been fine.

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  • efficiently convert string (or tuple) to ctypes array

    - by Mu Mind
    I've got code that takes a PIL image and converts it to a ctypes array to pass out to a C function: w_px, h_px = img.size pixels = struct.unpack('%dI'%(w_px*h_px), img.convert('RGBA').tostring()) pixels_array = (ctypes.c_int * len(pixels))(*pixels) But I'm dealing with big images, and unpacking that many items into function arguments seems to be noticeably slow. What's the simplest thing I can do to get a reasonable speedup? I'm only converting to a tuple as an intermediate step, so if it's unnecessary, all the better.

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  • Hi, i want to implement a small routing table for my learning? I know it is implemented using radix/

    - by aks
    Hi, i want to implement a small routing table for my learning? I know it is implemented using radix/patricia tree in routers? Can someone give me an idea on how to go about implementing the same? The major issue i feel is storing IP ADDRESS. For example : 10.1.1.0 network next hop 20.1.1.1 10.1.0.0 network next hop 40.1.1.1 Can someone give me a declaration of the struct from which i can have an idea?

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  • C++: incorrect swapping of nodes in linked list

    - by Dragon
    I have 2 simple structures: struct Address { char city[255]; }; typedef Address* AddressPtr; struct Person { char fullName[255]; Address* address; Person* next; }; typedef Person* PersonPtr; The Person structure forms the Linked list where new elements are added to the beginning of the list. What I want to do is to sort them by fullName. At first I tried to swap links, but I lost the beginning of the list and as a result my list was sorted partially. Then I decided to sort list by swapping the values of nodes. But I get strange results. For a list with names: Test3, Test2, Test1, I get Test3, Test3, Test3. Here is my sorting code: void sortByName(PersonPtr& head) { TaskPtr currentNode, nextNode; for(currentNode = head; currentNode->next != NULL; currentNode = currentNode->next) { for(nextNode = currentNode->next; nextNode != NULL; nextNode = nextNode->next) { if(strcmp(currentNode->fullName, nextNode->fullName) > 0) { swapNodes(currentNode, nextNode); } } } } void swapNodes(PersonPtr& node1, PersonPtr& node2) { PersonPtr temp_node = node2; strcpy(node2->fullName, node1->fullName); strcpy(node1->fullName, temp_node->fullName); strcpy(node2->address->city, node1->address->city); strcpy(node1->address->city, temp_node->address->city); } After the sorting completion, nodes values are a little bit strange. UPDATED This is how I swapped links void swapNodes(PersonPtr& node1, PersonPtr& node2) { PersonPtr temp_person; AddressPtr temp_address; temp_person = node2; node2 = node1; node1 = temp_person; temp_address = node2->address; node2->address = node1->address; node1->address = temp_address; }

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  • 'Invalid conversion from some_type** to const some_type**'

    - by petersohn
    I've got a function that requires const some_type** as an argument (some_type is a struct, and the function needs a pointer to an array of this type). I declared a local variable of type some_type*, and initialized it. Then I call the function as f(&some_array), and the compiler (gcc) says: error: invalid conversion from ‘some_type**’ to ‘const some_type**’ What's the problem here? Why can't I convert a variable to const?

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  • PHP text parsing and / or make your own language?

    - by AlexanderJohannesen
    Been Googling around without finding much at all, so does anyone know of a class or library that helps you parse any sort of language, like a Domain Specific Language (I'm creating one, so I'm flexible in what the syntax and format can be) into either PHP code or some helpful struct or a class hiearchy or ... ? Anything goes at this point. :) I want to experiment with parsing text files into tokens, building up a small grammar and syntax library to express things like Business Natural Languages.

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  • What is tagged structure initialization syntax?

    - by httpinterpret
    struct file_operations scull_fops = { .owner = THIS_MODULE, .llseek = scull_llseek, .read = scull_read, .write = scull_write, .ioctl = scull_ioctl, .open = scull_open, .release = scull_release, }; This declaration uses the standard C tagged structure initialization syntax. Can someone elaborate?

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  • How to call DLL function in vbscript

    - by amritad
    I am writing VB script in which I have to call a function of a COM DLL. The fuction which I want to use is in structure and thus I want to create the object of that structure to access the required function. e.g. I have a dll 'BasicCom.dll', in which struct abc { bool xyz(); } Now I want to call xyz(). Is any one have any idea, how to deal with such call in Vb script.

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  • Flexible array member in C-structure

    - by Arpan
    Quoting from the C-std section 6.7.2.1, struct s { int n; double d[]; }; This is a valid structure declaration. I am looking for some practical use of this kind of syntax. To be precise, how is this construct any more or less powerful than keeping a double* as the 2nd element? Or is this another case of 'you-can-do-it-in-multiple-ways'? Arpan

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  • Why is this undefined behaviour?

    - by xryl669
    Here's the sample code: X * makeX(int index) { return new X(index); } struct Tmp { mutable int count; Tmp() : count(0) {} const X ** getX() const { static const X* x[] = { makeX(count++), makeX(count++) }; return x; } }; This reports Undefined Behaviour on CLang version 500 in the static array construction. For sake of simplication for this post, the count is not static, but it does not change anything.

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  • How to push_back without operator=() for const members?

    - by WilliamKF
    How to push_back() to a C++ std::vector without using operator=() for which the default definition violates having const members? struct Item { Item(int value) : _value(value) { } const int _value; } vector<Item> items; items.push_back(Item(3)); I'd like to keep the _value const since it should not change after the object is constructed, so the question is how do I initialize my vector with elements without invoking operator=()?

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  • relaxng schema - use attributes for members and elements for structures?

    - by rpkrpk
    For a data-binding application, I am trying to draw parallels among RelaxNG, C++ and C. RelaxNG.Elements === C++.Class === C.Struct RelaxNG.Attributes === C++.class-members === C.structure-members Only that the Elements in RelaxNG can also have a data-type (i.e. it seems Attribute is a special case of the Element). Do I have the above equivalence correct? If I use the above convention in my implementation, will I be breaking some data-binding libraries?

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  • Go - Data types for validation

    - by nevalu
    How to create a new data type for Go which to can check/validate its schema when is created a new variable (of that type)? By example, to validate if a string has 20 characters, I tried: // Format: 2006-01-12T06:06:06Z func date(str string) { if len(str) != 20 { fmt.Println("error") } } var Date = date() type Account struct { domain string username string created Date } but it fails because Date is not a type.

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  • any stl/boost functors to call operator()

    - by Voivoid
    template <typename T> struct Foo { void operator()(T& t) { t(); } }; Is there any standart or boost functor with the similar implementation? I need it to iterate over container of functors: std::for_each(beginIter, endIter, Foo<Bar>()); Or maybe there are other way to do it?

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  • How to ensure structures are completly initialized (by name) in GCC?

    - by Steven Spark
    How do I ensure each and every field of my structures are initialized in GCC when using designated initializers? (I'm especially interested in function pointers.) (I'm using C not C++.) Here is an example: typedef struct { int a; int b; } foo_t; typedef struct { void (*Start)(void); void (*Stop)(void); } bar_t; foo_t fooo = { 5 }; foo_t food = { .b=4 }; bar_t baro = { NULL }; bar_t bard = { .Start = NULL }; -Wmissing-field-initializers does not help at all. It works for fooo only in GCC (mingw 4.7.3, 4.8.1), and clang does only marginally better (no warnings for food and bard). I'm sure there is a reason for not producing warnings for designated initializer (even when I explicitly ask for them) but I want/need them. I do not want to initialize structures based on order/position because that is more error prone (for example swapping Start and Stop won't even give any warning). And neither gcc nor clang will give any warning that I failed to explicitly initialize a field (when initializing by name). I also don't want to litter my code with if(x.y==NULL) lines for multiple reasons, one of which is I want compile time warnings and not runtime errors. At least splint will give me warnings on all 4 cases, but unfortunately I cannot use splint all the time (it chokes on some of the code (fails to parse some C99, GCC extensions)). Note: If I'm using a real function instead of NULL GCC will also show a warning for baro (but not bard). I searched google and stack overflow but only found related questions and have not found answer for this specific problem. The best match I have found is 'Ensure that all elements in a structure are initialized' Ensure that all elements in a structure are initialized Which asks pretty much the same question, but has no satisfying answer. Is there a better way dealing with this that I have not mentioned? (Maybe other code analysis tool? Preferably something (free) that can be integrated into Eclipse or Visual Studio...)

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