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  • C++ STL map.find() not finding my stuff

    - by Joe
    Hello, I have constructed a map and loaded it with data. If I iterate over all the elements I see they are all valid. However, the find method doesn't find my item. I'm sure it's something stupid I am doing. Here is snippet: // definitions // I am inserting a person class and using the firstname as the key typedef std::map<char*,Person *> mapType; mapType _myMap; mapType::iterator _mapIter; ... Person *pers = new Person(FirstName, LastName, Address, Phone); _myMap.insert(make_pair(pers->firstName, pers); ... ...later.... _mapIter = _myMap.find(firstName); // returns map.end _mapIter = _myMap.find("joe"); // returns map.end and I have no idea why :(

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  • some verd problems in qt

    - by prabhakaran
    I am very new to qt, So whatever I facing is either errors or problems. Here goes some of them, 1)Just try to install it in VisualStudio, you will got enough for the day. 2)After you installed it as a separate qt(without embedding it inside visual studio).Open a c++ file in qt, = then you won't get any option to compile it. 3)Create a empty qt4 project like below #include<iostream> using namespace std; int main(int a,char * argv[]) { } Then build it, you will get a error like this C:\qt-greenhouse\Trolltech\Code_less_create_more\Trolltech\Code_less_create_more\Troll\4.6\qt\src\winmain/qtmain_win.cpp:131: undefined reference to `qMain(int, char**)' Can anybody clear any of these problems to me.

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  • Why won't this compile and how can it be implemented so that it does?

    - by George Edison
    Here is some C++ code I'm playing around with: #include <iostream> #include <vector> #define IN , #define FOREACH(x,y) for(unsigned int i=0;i<y.size();i++) { x=y[i]; #define ENDFOREACH } using namespace std; int main() { vector<int> ints; ints.push_back(3); ints.push_back(4); ints.push_back(5); ints.push_back(6); FOREACH(int item IN ints) cout << item; ENDFOREACH return 0; } However, I get an error: macro "FOREACH" requires 2 arguments, but only 1 given The code compiles if I change the IN to a comma. How can I get the IN to take the place of a comma?

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  • Are pointers primitive types in C++?

    - by Space_C0wb0y
    I was wondering about the last constructor for std::string mentioned here. It says: template<class InputIterator> string (InputIterator begin, InputIterator end); If InputIterator is an integral type, behaves as the sixth constructor version (the one right above this) by typecasting begin and end to call it: string(static_cast<size_t>(begin),static_cast<char>(end)); In any other case, the parameters are taken as iterators, and the content is initialized with the values of the elements that go from the element referred by iterator begin to the element right before the one referred by iterator end. So what does that mean if InputIterator is a char * ?

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  • Behavior with primitive data types' value out of range & C99's PRI* macros

    - by Yktula
    Say we have an 8-bit unsigned integer n (UINT8_MAX=255); what is the behavior of the compiler for n=256? Where can I find a table of default behavior when the value of a data type is out of range for different data types? Is there a pattern to how they behave when set out of range? #include <stdio.h> #include <inttypes.h> uint8_t n = UINT8_MAX; int main() { printf("%hhu ",n++); printf("%hhu",n); return 0; } Compiling with gcc -std=c99 -Wall *.c, this prints: 255 0 Also, is it acceptable to use C99's PRI* macros? How are they named?

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  • Pure virtual destructor in interface

    - by ALOR
    Hello all. Here is my problem. I'm making C++ dll, which extensively relies on instance object exports. So i return my actual instances as a pointers to interface through some exported factory method. Interfaces i use are purely virtual, to avoid linking problame. So i need a pure virtual destructor too, and i implemented one (with empty body, as i googled it). All compiles perfectly well, except... I can't see, if the actual destructors are called or not - because when i added some std::cout << "hello destructor"; i never get to see it. I have some explicit "delete obj", that's not the problem. Am i missing something? Is there another way to delete my object through interface?

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  • Why is this c++ string concatenation missing a space?

    - by danutenshu
    I am working with c++ strings, and am a beginner at programming. I am expecting: 99 Red Balloons But I am receiving: 99 RedBalloons Why is that? #include <string> #include <iostream> using namespace std; int main() { string text = "9"; string term( "9 "); string info = "Toys"; string color; char hue[4] = {'R','e','d','\0'}; color = hue; info = "Balloons"; text += (term + color + info); cout << endl << text << endl; return 0; }

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  • read pair of characters separated by \t c++

    - by Kiran
    Friends, I want to read a pair of characters separated by \t. I want to continue reading the input until user enters z for any of the characters. Here are the options I thought: while (cinch1ch2) { // process ch1 & ch2 } std::string str; while (getline(cin, str) ){ //split string } Also, I want to validate the input to make sure that it is correct. Please suggest the best way. If this is a duplicate, please point me to the right one. Thanks.

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  • the problem only happens when i try create a release...

    - by ace
    I'm sorry if im not presenting this right, but i trully cannot understand what the problem is. i have a project to hand in, a code of 600 lines defined within a main, .cpp, and header file. if i compile the project with just a debugger and no release, it's fine. when i create it with the release, the following error occurs, for every function!!! 1st error: |36|multiple definition of `countLines(int&, std::vector const&)'| 2nd error: |36|first defined here| if someone will allow me and i can send them the entire code, that would be awesome - i have to have this done within 3 hours.

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  • How might I assume a "default value" when parsing using boost::spirit?

    - by tJener
    Let's say I have a grammar defined to something like: a b c d where c, and d are optional and default to 14 if not given. Can I get it to automatically return the 14 if the value isn't given? The closest I've come is like the following: qi::rule<Iterator, std::vector<int>(), ascii::space_type> some_rule; some_rule %= >> int_ >> int_ >> -int_ >> -int_; // ... some_other_rule = some_rule[&some_callback_for_int_vectors]; which will then get 0 for the optional values that didn't show up (I believe). I then change consecutive 0s at the end into 14. Not only is this horribly wrong, but its also just not elegant. Is there a better way to do this?

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  • c++ function overloading, making fwrite/fread act like PHP versions

    - by Newbie
    I'm used to the PHP fwrite/fread parameter orders, and i want to make them the same in C++ too. I want it to work with char and string types, and also any data type i put in it (only if length is defined). I am total noob on c++, this is what i made so far: size_t fwrite(FILE *fp, const std::string buf, const size_t len = SIZE_MAX){ if(len == SIZE_MAX){ return fwrite(buf.c_str(), 1, buf.length(), fp); }else{ return fwrite(buf.c_str(), 1, len, fp); } } size_t fwrite(FILE *fp, const void *buf, const size_t len = SIZE_MAX){ if(len == SIZE_MAX){ return fwrite((const char *)buf, 1, strlen((const char *)buf), fp); }else{ return fwrite(buf, 1, len, fp); } } Should this work just fine? And how should this be done if i wanted to do it the absolutely best possible way?

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  • Building a world matrix

    - by DeadMG
    When building a world projection matrix from scale, rotate, translate matrices, then the translation matrix must be the last in the process, right? Else you'll be scaling or rotating your translations. Do scale and rotate need to go in a specific order? Right now I've got std::for_each(objects.begin(), objects.end(), [&, this](D3D93DObject* ptr) { D3DXMATRIX WVP; D3DXMATRIX translation, rotationX, rotationY, rotationZ, scale; D3DXMatrixTranslation(&translation, ptr->position.x, ptr->position.y, ptr->position.z); D3DXMatrixRotationX(&rotationX, ptr->rotation.x); D3DXMatrixRotationY(&rotationY, ptr->rotation.y); D3DXMatrixRotationZ(&rotationZ, ptr->rotation.z); D3DXMatrixScaling(&translation, ptr->scale.x, ptr->scale.y, ptr->scale.z); WVP = rotationX * rotationY * rotationZ * scale * translation * ViewProjectionMatrix; });

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  • How to interrupt a waiting C++0x thread?

    - by doublep
    I'm considering to use C++0x threads in my application instead of Boost threads. However, I'm not sure how to reimplement what I have with standard C++0x threads since they don't seem to have an interrupt() method. My current setup is: a master thread that manages work; several worker threads that carry out master's commands. Workers call wait() on at least two different condition variables. Master has a "timed out" state: in this case it tells all workers to stop and give whatever result they got by then. With Boost threads master just uses interrupt_all() on a thread group, which causes workers to stop waiting. In case they are not waiting at the moment, master also sets a bool flag which workers check periodically. However, in C++0x std::thread I don't see any replacement for interrupt(). Do I miss something? If not, how can I implement the above scheme so that workers cannot just sleep forever?

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  • How can I output the fitted values?

    - by zenbomb
    Sorry if this is a novice question, but I don't understand it. I am fitting a sigmoid curve to my data with glm(). This works, I can plot the output and I see a nice sigmoid curve. However, how do I get R to return the final values it has fit? As I understand it, R fits the data to logit(y) = b0 + b1x, but when I do > summary(glm.out) I only get Call: glm(formula = e$V2 ~ e$V1, family = binomial(logit), data = e) Deviance Residuals: 1 2 3 4 5 6 7 -0.00001 -0.06612 -0.15118 -0.34237 0.20874 0.08724 -0.19557 Coefficients: Estimate Std. Error z value Pr(>|z|) (Intercept) -24.784 20.509 -1.208 0.227 e$V1 2.073 1.725 1.202 0.229 (Dispersion parameter for binomial family taken to be 1) Null deviance: 4.60338 on 6 degrees of freedom Residual deviance: 0.23388 on 5 degrees of freedom AIC: 5.8525 Number of Fisher Scoring iterations: 8 How do I get b0 and b1?

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  • Returning new base class when the parent class shared pointer is the return type

    - by Ben Dol
    Can you have a parent class shared pointer return type of a function and then return a new child class without it being a shared pointer? I'm not sure how shared pointers work in these situations, do they act like a regular pointer? Here is my example: BaseEventPtr Actions::getEvent(const std::string& nodeName) { if(asLowerCaseString(nodeName) == "action") return new ActionEvent(&m_interface); return nullptr; } ActionEvent is the subclass of BaseEvent in this situation. Cheers!

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  • problem in reading output of dd command using pipe

    - by Ummar
    I am developing an application, in which I want to redirect the output (progress information) of dd command to my C++ program, but it is not actually getting the output, here is the code FILE * progressInfo = popen("gzip -dc backup/backup.img.gz | pv -ptrbe -i 2 -s 2339876653 | dd of=/dev/sdb","r"); if(!progressInfo) { return -1; } char buf[1024]; while(fgets(buff, sizeof(buff),progressInfo)!=NULL) { std::cout << buff << endl; } but the problem is the progress information is not received in buff, and the output is continuously printed on terminal, and above program halts on while(fgets(buff, sizeof(buff),progressInfo)!=NULL), and as soon as the dd operation is completed, the very next line to loop block is executed. if anyone has any idea why the output is not returned to buff, and its continuously retuned on terminal?

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  • Segfault when calling a method c++

    - by shuttle87
    I am fairly new to c++ and I am a bit stumped by this problem. I am trying to assign a variable from a call to a method in another class but it always segfaults. My code compiles with no warnings and I have checked that all variables are correct in gdb but the function call itself seems to cause a segfault. The code I am using is roughly like the following: class History{ public: bool test_history(); }; bool History::test_history(){ std::cout<<"test"; //this line never gets executed //more code goes in here return true; } class Game{ private: bool some_function(); public: History game_actions_history; bool local_variable; }; bool Game::some_function(){ local_variable = game_actions_history.test_history(); if (local_variable == true){ return true; } else{ return false; } } Any tips or advice is greatly appreciated!

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  • vector segmentation fault

    - by user1849298
    I have a problem with the segmentation fault. Look: #include<fstream> using namespace std; int main(){ int n,i,vector[10001],vectorcopy[10001]; ifstream in("program.in"); ofstream out("program.out"); in>>n; for(i=1;i<=n;i++){ in>>vector[i]; vectorcopy[i]=vector[i]; } return 0;} And the debugger says: Program recived signal SIGSEGV, Segmentation fault Please, tell me what to do!

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  • OpenCv not initializing usb camera

    - by brainbarshan
    I am trying to capture video from usb camera using OpenCv. #include <highgui.h> #include <iostream> using namespace std; using namespace cv ; int main() { VideoCapture cap (-1); if(!cap.isOpened()) cout << "Cam initialize failed" ; else cout << "Cam initialized" ; return 0; } It is failing to initialize the camera. cap.isOpened() is returning zero. The same program, with same version of OpenCv and same usb camera, is correctly running in my friend's machine. I am running fedora 16. I did some searching in Google and Stack Overflow. But no useful help. Any idea ?

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  • Does C++ have a static polymorphism implementation of interface that does not use vtable?

    - by gilbertc
    Does C++ have a proper implementation of interface that does not use vtable? for example class BaseInterface{ public: virtual void func() const = 0; } class BaseInterfaceImpl:public BaseInterface{ public: void func(){ std::cout<<"called."<<endl; } } BaseInterface* obj = new BaseInterfaceImpl(); obj->func(); the call to func at the last line goes to vtable to find the func ptr of BaseInterfaceImpl::func, but is there any C++ way to do that directly as the BaseInterfaceImpl is not subclassed from any other class besides the pure interface class BaseInterface? Thanks. Gil.

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  • HowTo parse numbers from string with BOOST methods?

    - by mosg
    Problem: Visual C++ 10 project (using MFC and Boost libraries). In one of my methods I'm reading simple test.txt file. Here is what inside of the file (std::string): 12 asdf789, 54,19 1000 nsfewer:22!13 Then I'm reading it and I have to convert all digits to int only with boost methods. For example, I have a list of different characters which I have to parse: ( ’ ' ) ( [ ], ( ), { }, ? ? ) ( : ) ( , ) ( ! ) ( . ) ( - ) ( ? ) ( ‘ ’, “ ”, « » ) ( ; ) ( / ) And after conversation I must have some kind of a massive of int's values, like this one: 12,789,54,19,1000,22,13 Maybe some one already did this job? PS. I'm new for boost. Thanks!

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  • Excess elements in scalar initializer

    - by Wade Williams
    I'm pretty noobish when it comes to C++ STL stuff. After a compiler upgrade, I'm getting: error: Semantic Issue: Excess elements in scalar initializer on the call: Certificate *tempcert; cValType( tempPerson->name, tempcert ); with a typedef of: typedef std::map< string, certificate* >::value_type cValType; I'm not certain what this error is telling me or how to fix it. (Ok, I realize it's telling me excess elements, but it looks like it matches the map prototype to me, so I'm confused.) Suggestions?

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  • What to return as an iterator when there is no container?

    - by DaClown
    I have an inheritance structure of objects with begin() and end() as pure virtual member functions in the base class. From this objects I'm planning to build a composite structure. This inner objects have std::vector member the begin() and end() get their data from. But in a leaf class there is no vector. Now I try to find a return value for begin() and end() in the leaf classes. What would be a good way to do that? The easiest way would be to have a vector member in the leaf classes with no elements in it to fuel begin() and end(), but this just doesn't feel right.

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