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  • ifstream Open function not working

    - by Dave Swersky
    I've been all over the ifstream questions here on SO and I'm still having trouble reading a simple text file. I'm working with Visual Studio 2008. Here's my code: // CPPFileIO.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include <fstream> #include <conio.h> #include <iostream> #include <string> using namespace std; int _tmain(int argc, _TCHAR* argv[]) { ifstream infile; infile.open("input.txt", ifstream::in); if (infile.is_open()) { while (infile.good()) cout << (char) infile.get(); } else { cout << "Unable to open file."; } infile.close(); _getch(); return 0; } I have confirmed that the input.txt file is in the correct "working directory" by checking the value of argv[0]. The Open method just won't work. I'm also having trouble debugging- should I not be able to set a watch on "infile.good()" or "infile.is_open()"? I keep getting "Error: member function not present." EDIT: Updated code listing with full code from .CPP file. UPDATE: The file was NOT in the Current Working Directory. This is the directory where the project file is located. Moved it there and it works when debugging in VS.NET.

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  • How to parse kanji numeric characters using ICU?

    - by Aki
    I'm writing a function using ICU to parse an Unicode string which consists of kanji numeric character(s) and want to return the integer value of the string. "?" = 5 "???" = 31 "???????" = 5972 I'm setting the locale to Locale::getJapan() and using the NumberFormat::parse() to parse the character string. However, whenever I pass it any Kanji characters, the parse() method is returning U_INVALID_FORMAT_ERROR. Does anyone know if ICU supports Kanji character strings in the NumberFormat::parse() method? I was hoping that since I'm setting the Locale to Japanese that it would be able to parse Kanji numeric values. Thanks! #include <iostream> #include <unicode/numfmt.h> using namespace std; int main(int argc, char **argv) { const Locale &jaLocale = Locale::getJapan(); UErrorCode status = U_ZERO_ERROR; NumberFormat *nf = NumberFormat::createInstance(jaLocale, status); UChar number[] = {0x4E94}; // Character for '5' in Japanese '?' UnicodeString numStr(number); Formattable formattable; nf->parse(numStr, formattable, status); if (U_FAILURE(status)) { cout << "error parsing as number: " << u_errorName(status) << endl; return(1); } cout << "long value: " << formattable.getLong() << endl; }

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  • operator<< overload,

    - by mr.low
    //using namespace std; using std::ifstream; using std::ofstream; using std::cout; class Dog { friend ostream& operator<< (ostream&, const Dog&); public: char* name; char* breed; char* gender; Dog(); ~Dog(); }; im trying to overload the << operator. I'm also trying to practice good coding. But my code wont compile unless i uncomment the using namespace std. i keep getting this error and i dont know. im using g++ compiler. Dog.h:20: error: ISO C++ forbids declaration of ‘ostream’ with no type Dog.h:20: error: ‘ostream’ is neither function nor member function; cannot be declared friend. if i add line using std::cout; then i get this error. Dog.h:21: error: ISO C++ forbids declaration of ‘ostream’ with no type. Can somebody tell me the correct way to overload the << operator with out using namespace std;

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  • Multiple Instances of Static Singleton

    - by Nexus
    I've recently been working with code that looks like this: using namespace std; class Singleton { public: static Singleton& getInstance(); int val; }; Singleton &Singleton::getInstance() { static Singleton s; return s; } class Test { public: Test(Singleton &singleton1); }; Test::Test(Singleton &singleton1) { Singleton singleton2 = Singleton::getInstance(); singleton2.val = 1; if(singleton1.val == singleton2.val) { cout << "Match\n"; } else { cout << "No Match " << singleton1.val << " - " << singleton2.val << "\n"; } } int main() { Singleton singleton = Singleton::getInstance(); singleton.val = 2; Test t(singleton); } Every time I run it I get "No Match". From what I can tell when stepping through with GDB is that there are two instances of the Singleton. Why is this?

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  • x-dom-event-stream in Opera 10 Only Working on First Event

    - by Brad
    I have a python script (in the CherryPy framework) that sends Event: and data: text as this Opera blog post describes to a client browser. The javascript that recieves the x-dom-event-stream content is almost identical to what they show in the blog post. However, the browser displays only the first event sent. Anyone know what I'm missing? I tried a few older versions of Opera and found that it works in Opera 9.52 but not in any newer versions. What did they change? Here is the python code: class dumpData(object): def index(self): cherrypy.response.headers['Content-Type'] = "application/x-dom-event-stream" def yieldData(): i = 0 while 1: yield "Event: count\n" yield "data: " yield i yield "\n\n" i = i + 1 time.sleep(3); return yieldData() index._cp_config = {'response.stream': True} index.exposed = True And here is the javascript/html. Making a request to /data/ runs the python function above. <head> <script> onload = function() { document.getElementById("count").addEventListener("cout", cout, false); } function count(e) { document.getElementById("stream").firstChild.nodeValue = e.data; } </script> <event-source id="count" src="/data/"> </head> <body> <div id="stream"></div> </body> Opening the direct /data/ url in Firefox saves the stream to a file. So I know the output is in the correct format and that the stream works at all.

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  • string parsing to double fails in C++ (Xcode problem?)

    - by helixed
    Here's a fun one I've been trying to figure out. I have the following program: #include <iostream> #include <string> #include <sstream> using namespace std; int main(int argc, char *argv[]) { string s("5"); istringstream stream(s); double theValue; stream >> theValue; cout << theValue << endl; cout << stream.fail(); } The output is: 0 1 I don't understand why this is failing. Could somebody please tell me what I'm doing wrong? Thanks, helixed EDIT: Okay, sorry to turn this into a double post, but this looks like a problem specific to Xcode. If I compile this in g++, the code works without a problem. Does anybody have an idea why this is happening in Xcode, and how I could possibly fix it? Thanks again, helixed

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  • cannot use obsolete binding at ‘input’ because it has a destructor

    - by ihm
    here's the word-count I wrote. I got this error: cannot use obsolete binding at ‘input’ because it has a destructor and error: name lookup of ‘input’ changed for ISO ‘for’ scoping what are they suppose to mean? thanks in advance. //rewrite the word-count program using insert instead of subscripting #include <iostream> #include <utility> #include <map> #include <string> using namespace std; int main () { cout<<"please enter some words"<<endl; map<string,int> word_count; for(string input; cin>>input; ) if(!word_count.insert(make_pair(input,1)).second); ++word_count[input]; for(map<string,int>::iterator iter=word_count.begin(); iter!=word_count.end(); ++iter) cout<<iter->first<<": "<<iter->second<<endl; return 0; }

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  • Vector of pointers to base class, odd behaviour calling virtual functions

    - by Ink-Jet
    I have the following code #include <iostream> #include <vector> class Entity { public: virtual void func() = 0; }; class Monster : public Entity { public: void func(); }; void Monster::func() { std::cout << "I AM A MONSTER" << std::endl; } class Buddha : public Entity { public: void func(); }; void Buddha::func() { std::cout << "OHMM" << std::endl; } int main() { const int num = 5; // How many of each to make std::vector<Entity*> t; for(int i = 0; i < num; i++) { Monster m; Entity * e; e = &m; t.push_back(e); } for(int i = 0; i < num; i++) { Buddha b; Entity * e; e = &b; t.push_back(e); } for(int i = 0; i < t.size(); i++) { t[i]->func(); } return 0; } However, when I run it, instead of each class printing out its own message, they all print the "Buddha" message. I want each object to print its own message: Monsters print the monster message, Buddhas print the Buddha message. What have I done wrong?

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  • C++ Newbie: Passing an fstream to a function to read data

    - by vgm64
    I have a text file named num.txt who's only contents is the line 123. Then I have the following: void alt_reader(ifstream &file, char* line){ file.read(line, 3); cout << "First Time: " << line << endl; } int main() { ifstream inFile; int num; inFile.open("num.txt"); alt_reader(inFile, (char*)&num); cout << "Second Time: " << num << endl; } The output is: First Time: 123 Second Time: 3355185 Can you help me figure out how to get an fstream that is read in a function still assign the variable in main? I'm doing this because alt_reader really has a lot more to it, but this is the part I'm stuck on. Thanks a lot for the help.

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  • Singleton with inheritance, Derived class is not able to get instantiated in parent?

    - by yesraaj
    Below code instantiates a derived singleton object based on environment variable. The compiler errors saying error C2512: 'Dotted' : no appropriate default constructor. I don't understand what the compiler is complaining about. #include <stdlib.h> #include <iostream> #include <string> using namespace std; class Dotted; class Singleton{ public: static Singleton instant(){ if (!instance_) { char * style = getenv("STYLE"); if (!style){ if (strcmp(style,"dotted")==0) { instance_ = new Dotted(); return *instance_; } } else{ instance_ = new Singleton(); return *instance_; } } return *instance_; } void print(){cout<<"Singleton";} ~Singleton(){}; protected: Singleton(){}; private: static Singleton * instance_; Singleton(const Singleton & ); void operator=(const Singleton & ); }; class Dotted:public Singleton{ public: void print(){cout<<"Dotted";} protected: Dotted(); }; Dotted::Dotted():Singleton(){} int main(){ Singleton::instant().print(); cin.get(); }

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  • I'm having trouble with using std::stack to retrieve the values from a recursive function.

    - by Peter Stewart
    Thanks to the help I received in this post: http://stackoverflow.com/questions/2761918/how-do-i-use-this-in-a-member-function I have a nice, concise recursive function to traverse a tree in postfix order: void Node::postfix() { if (left != __nullptr) { left->postfix(); } if (right != __nullptr) { right->postfix(); } cout<<cargo<<"\n"; return; }; Now I need to evaluate the values and operators as they are returned. My problem is how to retrieve them. I tried the std::stack: #include <stack> stack <char*> s; void Node::postfix() { if (left != __nullptr) { left->postfix(); } if (right != __nullptr) { right->postfix(); } s.push(cargo); return; }; but when I tried to access it in main() while (!s.empty()) { cout<<s.top<<"\n"; s.pop; } I got the error: 'std::stack<_Ty::top': function call missing argument list; use '&std::stack<_Ty::top' to create a pointer to member' I'm stuck. Another question to follow shortly.

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  • Function that prints something to std::ostream and returns std::ostream?

    - by dehmann
    I want to write a function that outputs something to a ostream that's passed in, and return the stream, like this: std::ostream& MyPrint(int val, std::ostream* out) { *out << val; return *out; } int main(int argc, char** argv){ std::cout << "Value: " << MyPrint(12, &std::cout) << std::endl; return 0; } It would be convenient to print the value like this and embed the function call in the output operator chain, like I did in main(). It doesn't work, however, and prints this: $ ./a.out 12Value: 0x6013a8 The desired output would be this: Value: 12 How can I fix this? Do I have to define an operator<< instead? UPDATE: Clarified what the desired output would be. UPDATE2: Some people didn't understand why I would print a number like that, using a function instead of printing it directly. This is a simplified example, and in reality the function prints a complex object rather than an int.

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  • Catching a nested-in-template exception [C++]

    - by Karol
    Hello, I have a problem with writing a catch clause for an exception that is a class nested in a template. To be more specific, I have a following definition of the template and exception: /** Generic stack implementation. Accepts std::list, std::deque and std::vector as inner container. */ template < typename T, template < typename Element, typename = std::allocator<Element> > class Container = std::deque > class stack { public: class StackEmptyException { }; ... /** Returns value from the top of the stack. Throws StackEmptyException when the stack is empty. */ T top() const; ... } I have a following template method that I want exception to catch: template <typename Stack> void testTopThrowsStackEmptyExceptionOnEmptyStack() { Stack stack; std::cout << "Testing top throws StackEmptyException on empty stack..."; try { stack.top(); } catch (Stack::StackEmptyException) { // as expected. } std::cout << "success." << std::endl; } When I compile it (-Wall, -pedantic) I get the following error: In function ‘void testTopThrowsStackEmptyExceptionOnEmptyStack()’: error: expected type-specifier error: expected unqualified-id before ‘)’ token === Build finished: 2 errors, 0 warnings === Thanks in advance for any help! What is interesting, if the stack implementation was not a template, then the compiler would accept the code as it is.

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  • How to determine the data type of a CvMat

    - by Chris
    When using the CvMat type, the type of data is crucial to keeping your program running. For example, depending on whether your data is type float or unsigned char, you would choose one of these two commands: cvmGet(mat, row, col); cvGetReal2D(mat, row, col); Is there a universal approach to this? If the wrong data type matrix is passed to these calls, they crash at runtime. This is becoming an issue, since a function I have defined is getting passed several different types of matrices. How do you determine the data type of a matrix so you can always access its data? I tried using the "type()" function as such. CvMat* tmp_ptr = cvCreateMat(t_height,t_width,CV_8U); std::cout << "type = " << tmp_ptr->type() << std::endl; This does not compile, saying "term does not evaluate to a function taking 0 arguments". If I remove the brackets after the word type, I get a type of 1111638032 EDIT minimal application that reproduces this... int main( int argc, char** argv ) { CvMat *tmp2 = cvCreateMat(10,10, CV_32FC1); std::cout << "tmp2 type = " << tmp2->type << " and CV_32FC1 = " << CV_32FC1 << " and " << (tmp2->type == CV_32FC1) << std::endl; } Output: tmp2 type = 1111638021 and CV_32FC1 = 5 and 0

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  • Problem Linking Boost Filesystem Library in Microsoft Visual C++

    - by Scott
    Hello. I am having trouble getting my project to link to the Boost (version 1.37.0) Filesystem lib file in Microsoft Visual C++ 2008 Express Edition. The Filesystem library is not a header-only library. I have been following the Getting Started on Windows guide posted on the official boost web page. Here are the steps I have taken: I used bjam to build the complete set of lib files using: bjam --build-dir="C:\Program Files\boost\build-boost" --toolset=msvc --build-type=complete I copied the /libs directory (located in C:\Program Files\boost\build-boost\boost\bin.v2) to C:\Program Files\boost\boost_1_37_0\libs. In Visual C++, under Project Properties Additional Library Directories I added these paths: C:\Program Files\boost\boost_1_37_0\libs C:\Program Files\boost\boost_1_37_0\libs\filesystem\build\msvc-9.0express\debug\link-static\threading-multi I added the second one out of desperation. It is the exact directory where libboost_system-vc90-mt-gd-1_37.lib resides. In Configuration Properties C/C++ General Additional Include Directories I added the following path: C:\Program Files\boost\boost_1_37_0 Then, to put the icing on the cake, under Tools Options VC++ Directories Library files, I added the same directories mentioned in step 3. Despite all this, when I build my project I get the following error: fatal error LNK1104: cannot open file 'libboost_system-vc90-mt-gd-1_37.lib' Additionally, here is the code that I am attempting to compile as well as a screen shot of the aformentioned directory where the (assumedly correct) lib file resides: #include "boost/filesystem.hpp" // includes all needed Boost.Filesystem declarations #include <iostream> // for std::cout using boost::filesystem; // for ease of tutorial presentation; // a namespace alias is preferred practice in real code using namespace std; int main() { cout << "Hello, world!" << endl; return 0; } Can anyone help me out? Let me know if you need to know anything else. As always, thanks in advance.

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  • Changing associativity

    - by Sorush Rabiee
    Hi... The associativity of stream insertion operator is rtl, forgetting this fact sometimes cause to runtime or logical errors. for example: 1st- int F() { static int internal_counter c=0; return ++c; } in the main function: //....here is main() cout<<”1st=”<<F()<<”,2nd=”<<F()<<”,3rd=”<<F(); and the output is: 1st=3,2nd=2,3rd=1 that is different from what we expect at first look. 2nd- suppose that we have an implementation of stack data structure like this: // //... a Stack<DataType> class …… // Stack<int> st(10); for(int i=1;i<11;i++) st.push(i); cout<<st.pop()<<endl<<st.pop()<<endl<<st.pop()<<endl<<st.pop()<<endl; expected output is something like: 10 9 8 7 but we have: 7 8 9 10 There is no internal bug of << implementation but it can be so confusing... and finally[:-)] my question: is there any way to change assocativity of an operator by overloading it?

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  • C++ Returning a Reference

    - by Devil Jin
    Consider the following code where I am returning double& and a string&. The thing works fine in the case of a double but not in the case of a string. Why is this difference in the behavior? In both the cases compiler does not even throws the Warning: returning address of local variable or temporary as I am returning a reference. #include <iostream> #include <string> using namespace std; double &getDouble(){ double h = 46.5; double &hours = h; return hours; } string &getString(){ string str = "Devil Jin"; string &refStr = str; return refStr; } int main(){ double d = getDouble(); cout << "Double = " << d << endl; string str = getString(); cout << "String = " << str.c_str() << endl; return 0; } Output: $ ./a.exe Double = 46.5 String =

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  • Is it possible to use boost::bind to effectively concatenate functions?

    - by Catskul
    Assume that I have a boost::function of with an arbitrary signature called type CallbackType. Is it possible to use boost::bind to compose a function that takes the same arguments as the CallbackType but calls the two functors in succession? Hypothetical example using a magic template: Template<typename CallbackType> class MyClass { public: CallbackType doBoth; MyClass( CallbackType callback ) { doBoth = bind( magic<CallbackType>, protect( bind(&MyClass::alert, this) ), protect( callback ) ); } void alert() { cout << "It has been called\n"; } }; void doIt( int a, int b, int c) { cout << "Doing it!" << a << b << c << "\n"; } int main() { typedef boost::function<void (int, int, int)> CallbackType; MyClass<CallbackType> object( boost::bind(doIt) ); object.doBoth(); return 0; }

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  • Alright, I'm still stuck on this homework problem. C++

    - by Josh
    Okay, the past few days I have been trying to get some input on my programs. Well I decided to scrap them for the most part and try again. So once again, I'm in need of help. For the first program I'm trying to fix, it needs to show the sum of SEVEN numbers. Well, I'm trying to change is so that I don't need the mem[##] = ####. I just want the user to be able to input the numbers and the program run from there and go through my switch loop. And have some kind of display..saying like the sum is?.. Here's my code so far. #include <iostream> #include <iomanip> #include <ios> using namespace std; int main() { const int READ = 10; const int WRITE = 11; const int LOAD = 20; const int STORE = 21; const int ADD = 30; const int SUBTRACT = 31; const int DIVIDE = 32; const int MULTIPLY = 33; const int BRANCH = 40; const int BRANCHNEG = 41; const int BRANCHZERO = 42; const int HALT = 43; int mem[100] = {0}; //Making it 100, since simpletron contains a 100 word mem. int operation; //taking the rest of these variables straight out of the book seeing as how they were italisized. int operand; int accum = 0; // the special register is starting at 0 int counter; for ( counter=0; counter < 100; counter++) mem[counter] = 0; // This is for part a, it will take in positive variables in //a sent-controlled loop and compute + print their sum. Variables from example in text. mem[0] = 1009; mem[1] = 1109; mem[2] = 2010; mem[3] = 2111; mem[4] = 2011; mem[5] = 3100; mem[6] = 2113; mem[7] = 1113; mem[8] = 4300; counter = 0; //Makes the variable counter start at 0. while(true) { operand = mem[ counter ]%100; // Finds the op codes from the limit on the mem (100) operation = mem[ counter ]/100; //using a switch loop to set up the loops for the cases switch ( operation ){ case READ: //reads a variable into a word from loc. Enter in -1 to exit cout <<"\n Input a positive variable: "; cin >> mem[ operand ]; counter++; break; case WRITE: // takes a word from location cout << "\n\nThe content at location " << operand << " is " << mem[operand]; counter++; break; case LOAD:// loads accum = mem[ operand ];counter++; break; case STORE: //stores mem[ operand ] = accum;counter++; break; case ADD: //adds accum += mem[operand];counter++; break; case SUBTRACT: // subtracts accum-= mem[ operand ];counter++; break; case DIVIDE: //divides accum /=(mem[ operand ]);counter++; break; case MULTIPLY: // multiplies accum*= mem [ operand ];counter++; break; case BRANCH: // Branches to location counter = operand; break; case BRANCHNEG: //branches if acc. is < 0 if (accum < 0) counter = operand; else counter++; break; case BRANCHZERO: //branches if acc = 0 if (accum == 0) counter = operand; else counter++; break; case HALT: // Program ends break; } } return 0; } part B int main() { const int READ = 10; const int WRITE = 11; const int LOAD = 20; const int STORE = 21; const int ADD = 30; const int SUBTRACT = 31; const int DIVIDE = 32; const int MULTIPLY = 33; const int BRANCH = 40; const int BRANCHNEG = 41; const int BRANCHZERO = 41; const int HALT = 43; int mem[100] = {0}; int operation; int operand; int accum = 0; int pos = 0; int j; mem[22] = 7; // loop 7 times mem[25] = 1; // increment by 1 mem[00] = 4306; mem[01] = 2303; mem[02] = 3402; mem[03] = 6410; mem[04] = 3412; mem[05] = 2111; mem[06] = 2002; mem[07] = 2312; mem[08] = 4210; mem[09] = 2109; mem[10] = 4001; mem[11] = 2015; mem[12] = 3212; mem[13] = 2116; mem[14] = 1101; mem[15] = 1116; mem[16] = 4300; j = 0; while ( true ) { operand = memory[ j ]%100; // Finds the op codes from the limit on the memory (100) operation = memory[ j ]/100; //using a switch loop to set up the loops for the cases switch ( operation ){ case 1: //reads a variable into a word from loc. Enter in -1 to exit cout <<"\n enter #: "; cin >> memory[ operand ]; break; case 2: // takes a word from location cout << "\n\nThe content at location " << operand << "is " << memory[operand]; break; case 3:// loads accum = memory[ operand ]; break; case 4: //stores memory[ operand ] = accum; break; case 5: //adds accum += mem[operand];; break; case 6: // subtracts accum-= memory[ operand ]; break; case 7: //divides accum /=(memory[ operand ]); break; case 8: // multiplies accum*= memory [ operand ]; break; case 9: // Branches to location j = operand; break; case 10: //branches if acc. is < 0 break; case 11: //branches if acc = 0 if (accum == 0) j = operand; break; case 12: // Program ends exit(0); break; } j++; } return 0; }

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  • sizeof continues to return 4 instead of actual size

    - by Guest
    #include <iostream> using namespace std; int main() { cout << "Do you need to encrypt or decrypt?" << endl; string message; getline(cin, message); int letter2number; for (int place = 1; place < sizeof(message); place++) { letter2number = static_cast<int>(message[place]); cout << letter2number << endl; } } Examples of problem: I type fifteen letters but only four integers are printed. I type seven letters but only four integers are printed. The loop only occurs four times on my computer, not the number of characters in the string. This is the only problem I am having with it, so if you see other errors, please don't tell me. (It is more fun that way.) Thank you for your time.

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  • error C3662: override specifier 'new' only allowed on member functions of managed classes

    - by William
    Okay, so I'm trying to override a function in a parent class, and getting some errors. here's a test case #include <iostream> using namespace std; class A{ public: int aba; void printAba(); }; class B: public A{ public: void printAba() new; }; void A::printAba(){ cout << "aba1" << endl; } void B::printAba() new{ cout << "aba2" << endl; } int main(){ A a = B(); a.printAba(); return 0; } And here's the errors I'm getting: Error 1 error C3662: 'B::printAba' : override specifier 'new' only allowed on member functions of managed classes c:\users\test\test\test.cpp 12 test Error 2 error C2723: 'B::printAba' : 'new' storage-class specifier illegal on function definition c:\users\test\test\test.cpp 19 test How the heck do I do this?

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  • Internal "Tee" setup

    - by RadlyEel
    I have inherited some really old VC6.0 code that I am upgrading to VS2008 for building a 64-bit app. One required feature that was implemented long, long ago is overriding std::cout so its output goes simultaneously to a console window and to a file. The implementation depended on the then-current VC98 library implementation of ostream and, of course, is now irretrievably broken with VS2008. It would be reasonable to accumulate all the output until program termination time and then dump it to a file. I got part of the way home by using freopen(), setvbuf(), and ios::sync_with_stdio(), but to my dismay, the internal library does not treat its buffer as a ring buffer; instead when it flushes to the output device it restarts at the beginning, so every flush wipes out all my accumulated output. Converting to a more standard logging function is not desirable, as there are over 1600 usages of "std::cout << " scattered throughout almost 60 files. I have considered overriding ostream's operator<< function, but I'm not sure if that will cover me, since there are global operator<< functions that can't be overridden. (Or can they?) Any ideas on how to accomplish this?

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  • Can operator<< in derived class call another operator<< in base class in c++?

    - by ivory
    In my code, Manager is derived from Employee and each of them have an operator<< override. class Employee{ protected: int salary; int rank; public: int getSalary()const{return salary;} int getRank()const{return rank;} Employee(int s, int r):salary(s), rank(r){}; }; ostream& operator<< (ostream& out, Employee& e){ out << "Salary: " << e.getSalary() << " Rank: " << e.getRank() << endl; return out; } class Manager: public Employee{ public: Manager(int s, int r): Employee(s, r){}; }; ostream& operator<< (ostream& out, Manager& m){ out << "Manager: "; cout << (Employee)m << endl; //can not compile, how to call function of Employee? return out; } I hoped cout << (Employee)m << endl; would call ostream& operator<< (ostream& out, Employee& e), but it failed.

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  • BN_hex2bn magically segfaults in openSSL

    - by xunil154
    Greetings, this is my first post on stackoverflow, and i'm sorry if its a bit long. I'm trying to build a handshake protocol for my own project and am having issues with the server converting the clients RSA's public key to a Bignum. It works in my clent code, but the server segfaults when attempting to convert the hex value of the clients public RSA to a bignum. I have already checked that there is no garbidge before or after the RSA data, and have looked online, but i'm stuck. header segment: typedef struct KEYS { RSA *serv; char* serv_pub; int pub_size; RSA *clnt; } KEYS; KEYS keys; Initializing function: // Generates and validates the servers key /* code for generating server RSA left out, it's working */ //Set client exponent keys.clnt = 0; keys.clnt = RSA_new(); BN_dec2bn(&keys.clnt->e, RSA_E_S); // RSA_E_S contains the public exponent Problem code (in Network::server_handshake): // *Recieved an encrypted message from the network and decrypt into 'buffer' (1024 byte long)* cout << "Assigning clients RSA" << endl; // I have verified that 'buffer' contains the proper key if (BN_hex2bn(&keys.clnt->n, buffer) < 0) { Error("ERROR reading server RSA"); } cout << "clients RSA has been assigned" << endl; The program segfaults at BN_hex2bn(&keys.clnt->n, buffer) with the error (valgrind output) Invalid read of size 8 at 0x50DBF9F: BN_hex2bn (in /usr/lib/libcrypto.so.0.9.8) by 0x40F23E: Network::server_handshake() (Network.cpp:177) by 0x40EF42: Network::startNet() (Network.cpp:126) by 0x403C38: main (server.cpp:51) Address 0x20 is not stack'd, malloc'd or (recently) free'd Process terminating with default action of signal 11 (SIGSEGV) Access not within mapped region at address 0x20 at 0x50DBF9F: BN_hex2bn (in /usr/lib/libcrypto.so.0.9.8) And I don't know why it is, Im using the exact same code in the client program, and it works just fine. Any input is greatly appriciated!

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  • Why do pure virtual base classes get direct access to static data members while derived instances do

    - by Shamster
    I've created a simple pair of classes. One is pure virtual with a static data member, and the other is derived from the base, as follows: #include <iostream> template <class T> class Base { public: Base (const T _member) { member = _member; } static T member; virtual void Print () const = 0; }; template <class T> T Base<T>::member; template <class T> void Base<T>::Print () const { std::cout << "Base: " << member << std::endl; } template <class T> class Derived : public Base<T> { public: Derived (const T _member) : Base<T>(_member) { } virtual void Print () const { std::cout << "Derived: " << this->member << std::endl; } }; I've found from this relationship that when I need access to the static data member in the base class, I can call it with direct access as if it were a regular, non-static class member. i.e. - the Base::Print() method does not require a this- modifier. However, the derived class does require the this-member indirect access syntax. I don't understand why this is. Both class methods are accessing the same static data, so why does the derived class need further specification? A simple call to test it is: int main () { Derived<double> dd (7.0); dd.Print(); return 0; } which prints the expected "Derived: 7"

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