Search Results

Search found 1031 results on 42 pages for 'iostream'.

Page 26/42 | < Previous Page | 22 23 24 25 26 27 28 29 30 31 32 33  | Next Page >

• SHGetFolderPath

  - by user530589

  This code works for windows 7 but doesn't work for windows XP (outputs only part of startup folder path) #include <iostream> #include <shlobj.h> using namespace std; int main() { wchar_t startupFolder[1024]; HRESULT hr = SHGetFolderPath(0, CSIDL_STARTUP, 0, 0, startupFolder); if (SUCCEEDED(hr)) wcout << L"Startup folder = " << startupFolder << endl; else cout << "Error when getting startup folder\n"; getchar(); return 0; } output is: Startup folder = C:\Documents and Settings\Admin\ <- cursor is here. Newline is not provided. Also I have russian window xp. I think this is unicode issue. when I use wprintf I got: C:\Documents and Settings\Admin\???????? ..... Thanks. As a temporary solution: After SHGetFolderPath I call GetShortPathName then I get path in msdos style: C:\DOCUME~1\Admin\5D29~1\4A66~1\60C2~1 Not really beautiful solution, but at least that is a valid path.

  Read the article

• Array Assignment

  - by Mahesh

  Let me explain with an example - #include <iostream> void foo( int a[2], int b[2] ) // I understand that, compiler doesn't bother about the // array index and converts them to int *a, int *b { a = b ; // At this point, how ever assignment operation is valid. } int main() { int a[] = { 1,2 }; int b[] = { 3,4 }; foo( a, b ); a = b; // Why is this invalid here. return 0; } Is it because, array decays to a pointer when passed to a function foo(..), assignment operation is possible. And in main, is it because they are of type int[] which invalidates the assignment operation. Doesn't a,b in both the cases mean the same ? Thanks. Edit 1: When I do it in a function foo, it's assigning the b's starting element location to a. So, thinking in terms of it, what made the language developers not do the same in main(). Want to know the reason.

  Read the article

• C++: What is the size of an object of an empty class?

  - by Ashwin

  I was wondering what could be the size of an object of an empty class. It surely could not be 0 bytes since it should be possible to reference and point to it like any other object. But, how big is such an object? I used this small program: #include <iostream> using namespace std; class Empty {}; int main() { Empty e; cerr << sizeof(e) << endl; return 0; } The output I got on both Visual C++ and Cygwin-g++ compilers was 1 byte! This was a little surprising to me since I was expecting it to be of the size of the machine word (32 bits or 4 bytes). Can anyone explain why the size of 1 byte? Why not 4 bytes? Is this dependent on compiler or the machine too? Also, can someone give a more cogent reason for why an empty class object will not be of size 0 bytes?

  Read the article

• How to determine number of function arguments dynamically

  - by Kam

  I have the following code: #include <iostream> #include <functional> class test { public: typedef std::function<bool(int)> Handler; void handler(Handler h){h(5);} }; class test2 { public: template< typename Ret2, typename Ret, typename Class, typename Param> inline Ret2 MemFn(Ret (Class::*f)(Param), int arg_num) { if (arg_num == 1) return std::bind(f, this, std::placeholders::_1); } bool f(int x){ std::cout << x << std::endl; return true;} }; int main() { test t; test2 t2; t.handler(t2.MemFn<test::Handler>(&test2::f, 1)); return 0; } It works as expected. I would like to be able to call this: t.handler(t2.MemFn<test::Handler>(&test2::f)); instead of t.handler(t2.MemFn<test::Handler>(&test2::f, 1)); Basically I need MemFn to determine in runtime what Handler expects as the number of arguments. Is that even possible?

  Read the article

• C++ const-reference semantics?

  - by Kristoffer

  Consider the sample application below. It demonstrates what I would call a flawed class design. #include <iostream> using namespace std; struct B { B() : m_value(1) {} long m_value; }; struct A { const B& GetB() const { return m_B; } void Foo(const B &b) { // assert(this != &b); m_B.m_value += b.m_value; m_B.m_value += b.m_value; } protected: B m_B; }; int main(int argc, char* argv[]) { A a; cout << "Original value: " << a.GetB().m_value << endl; cout << "Expected value: 3" << endl; a.Foo(a.GetB()); cout << "Actual value: " << a.GetB().m_value << endl; return 0; } Output: Original value: 1 Expected value: 3 Actual value: 4 Obviously, the programmer is fooled by the constness of b. By mistake b points to this, which yields the undesired behavior. My question: What const-rules should you follow when designing getters/setters? My suggestion: Never return a reference to a member variable if it can be set by reference through a member function. Hence, either return by value or pass parameters by value. (Modern compilers will optimize away the extra copy anyway.)

  Read the article

• Confusion about pointers and their memory addresses

  - by TimothyTech

  alright, im looking at a code here and the idea is difficult to understand. #include <iostream> using namespace std; class Point { public : int X,Y; Point() : X(0), Y(0) {} }; void MoveUp (Point * p) { p -> Y += 5; } int main() { Point point MoveUp(&point) cout <<point.X << point.Y; return 0; } Alright, so i believe that a class is created and X and Y are declared and they are put inside a constructor a method is created and the argument is Point * p, which means that we are going to stick the constructor's pointer inside the function; now we create an object called point then call our method and put the pointers address inside it? isnt the pointers address just a memory number like 0x255255? and why wasnt p ever declared? (int * p = Y) what is a memory addres exactly? that it can be used as an argument?

  Read the article

• Should we use p(..) or (*p)(..) when p is a function pointer?

  - by q0987

  Reference: [33.11] Can I convert a pointer-to-function to a void*? #include "stdafx.h" #include <iostream> int f(char x, int y) { return x; } int g(char x, int y) { return y; } typedef int(*FunctPtr)(char,int); int callit(FunctPtr p, char x, int y) // original { return p(x, y); } int callitB(FunctPtr p, char x, int y) // updated { return (*p)(x, y); } int _tmain(int argc, _TCHAR* argv[]) { FunctPtr p = g; // original std::cout << p('c', 'a') << std::endl; FunctPtr pB = &g; // updated std::cout << (*pB)('c', 'a') << std::endl; return 0; } Question Which way, the original or updated, is the recommended method? Thank you Although I do see the following usage in the original post: void baz() { FredMemFn p = &Fred::f; ? declare a member-function pointer ... }

  Read the article

• Something missing

  - by DHF

  The error of "} expected" appears at line 5. Why is that? I have included it at line 15. The error of "Declaration missing ;" appears at line 8. Why? There is ";" at the end of the line. #include<iostream> using namespace std; class PEmployee { public: PEmployee(); PEmployee(string employee_name, double initial_salary); void set_salary(double new_salary); double get_salary() const; string get_name() const; private: Person person_data; double salary; }; //line 15 int main() { PEmployee f("Patrick", 1000.00); cout << f.get_name() << " earns a salary of " << f.get_salary() << endl; return 0; } Newbie here, sorry for unclear question

  Read the article

• why does vector.size() read in one line too little?

  - by ace

  when running the following code, the amount of lines will read on less then there actually is (if the input file is main itself, or otherwise) why is this and how can i change that fact (besides for just adding 1)? #include <fstream> #include <iostream> #include <string> #include <vector> using namespace std; int main() { // open text file for input string file_name; cout << "please enter file name: "; cin >> file_name; // associate the input file stream with a text file ifstream infile(file_name.c_str()); // error checking for a valid filename if ( !infile ) { cerr << "Unable to open file " << file_name << " -- quitting!\n"; return( -1 ); } else cout << "\n"; // some data structures to perform the function vector<string> lines_of_text; string textline; // read in text file, line by line while (getline( infile, textline, '\n' )) { // add the new element to the vector lines_of_text.push_back( textline ); // print the 'back' vector element - see the STL documentation cout << "line read: " << lines_of_text.back() << "\n"; } cout<<lines_of_text.size(); return 0; }

  Read the article

• This program isn't asking for the predetermined 5 numbers from the array?

  - by user1801781

  Okay, so this question is difficult to state. I'm a beginner at C++, and I rarely run into problems with these simple assignments, but something is majorly wrong here and I cannot identify it. I've been trying for hours. This program is supposed to read 5 numbers from an array that the user enters, and then print the largest one. (I know it's easier to just write a for-loop, but our professor wanted us to call a function). The only problem is that instead of asking for 5 numbers, it asks for 2. It works other than that, I JUST NEED IT TO ASK FOR 5 NUMBERS. haha. Your input would be greatly appreciated. I aspire to be a programmer one day, so don't be afraid to go harsh on me. #include <iostream> using namespace std; int largest_number(int score[], int max) { for (int i=1; i<5; i++) { cin >> score[i]; if(score[i] > max) max=score[i]; return (max); } } int main () { int score[5], max, z; cout << "Enter 5 numbers: " <<endl; cin >> score[0]; max = score[0]; z = largest_number(score, max); cout << "The largest number is: " << z <<endl; system("pause"); return 0; }

  Read the article

• std::thread and class constructor and destructor

  - by toeplitz

  When testing threads in C++11 I have created the following example: #include <iostream> #include <thread> class Foo { public: Foo(void) { std::cout << "Constructor called: " << this << std::endl; } ~Foo(void) { std::cout << "Destructor called: " << this << std::endl; } void operator()() const { std::cout << "Operatior called: " << this << std::endl; } }; void test_normal(void) { std::cout << "====> Standard example:" << std::endl; Foo f; } void test_thread(void) { std::cout << "====> Thread example:" << std::endl; Foo f; std::thread t(f); t.detach(); } int main(int argc, char **argv) { test_normal(); test_thread(); for(;;); } Which prints the following: Why is the destructor called 6 times for the thread? And why does the thread report different memory locations?

  Read the article

• boost::function & boost::lambda - call site invocation & accessing _1 and _2 as the type

  - by John Dibling

  Sorry for the confusing title. Let me explain via code: #include <string> #include <boost\function.hpp> #include <boost\lambda\lambda.hpp> #include <iostream> int main() { using namespace boost::lambda; boost::function<std::string(std::string, std::string)> f = _1.append(_2); std::string s = f("Hello", "There"); std::cout << s; return 0; } I'm trying to use function to create a function that uses the labda expressions to create a new return value, and invoke that function at the call site, s = f("Hello", "There"); When I compile this, I get: 1>------ Build started: Project: hacks, Configuration: Debug x64 ------ 1>Compiling... 1>main.cpp 1>.\main.cpp(11) : error C2039: 'append' : is not a member of 'boost::lambda::lambda_functor<T>' 1> with 1> [ 1> T=boost::lambda::placeholder<1> 1> ] Using MSVC 9. My fundamental understanding of function and lambdas may be lacking. The tutorials and docs did not help so far this morning. How do I do what I'm trying to do?

  Read the article

• Operator Overloading << in c++

  - by thlgood

  I'm a fresh man in C++. I write this simple program to practice Overlaoding. This is my code: #include <iostream> #include <string> using namespace std; class sex_t { private: char __sex__; public: sex_t(char sex_v = 'M'):__sex__(sex_v) { if (sex_v != 'M' && sex_v != 'F') { cerr << "Sex type error!" << sex_v << endl; __sex__ = 'M'; } } const ostream& operator << (const ostream& stream) { if (__sex__ == 'M') cout << "Male"; else cout << "Female"; return stream; } }; int main(int argc, char *argv[]) { sex_t me('M'); cout << me << endl; return 0; } When I compiler it, It print a lots of error message: The error message was in a mess. It's too hard for me to found useful message sex.cpp: ???‘int main(int, char**)’?: sex.cpp:32:10: ??: ‘operator<<’?‘std::cout << me’????? sex.cpp:32:10: ??: ???: /usr/include/c++/4.6/ostream:110:7: ??: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostre

  Read the article

• Is this an error in "More Effective C++" in Item28?

  - by particle128

  I encountered a question when I was reading the item28 in More Effective C++ .In this item, the author shows to us that we can use member template in SmartPtr such that the SmartPtr<Cassette> can be converted to SmartPtr<MusicProduct>. The following code is not the same as in the book,but has the same effect. #include <iostream> class Base{}; class Derived:public Base{}; template<typename T> class smart{ public: smart(T* ptr):ptr(ptr){} template<typename U> operator smart<U>() { return smart<U>(ptr); } ~smart(){delete ptr;} private: T* ptr; }; void test(const smart<Base>& ) {} int main() { smart<Derived> sd(new Derived); test(sd); return 0; } It indeed can be compiled without compilation error. But when I ran the executable file, I got a core dump. I think that's because the member function of the conversion operator makes a temporary smart, which has a pointer to the same ptr in sd (its type is smart<Derived>). So the delete directive operates twice. What's more, after calling test, we can never use sd any more, since ptr in sd has already been delete. Now my questions are : Is my thought right? Or my code is not the same as the original code in the book? If my thought is right, is there any method to do this? Thanks very much for your help.

  Read the article

• How to set up a functional macro with parameters in C++?

  - by user1728737

  is there a way that I can make this work? Or do I need to use separate files? #include <iostream> // Necessary using namespace std; long double primary, secondary, tertiary; #define long double mMaxOf2(long double min, long double max) { return ((max > min) ? (max) : (min)); } #define long double mMaxOf3(long double Min, long double Max, long double Mid) { long double Mid = (long double mMaxOf2(long double Min, long double Mid)); long double Max = (long double mMaxOf2(long double Mid, long double Max)); return (Max); } int main() { cout << "Please enter three numbers: "; cin << primary << secondary << tertiary; cout << "The maximum of " << primary << " " << secondary << " " << tertiary; cout << " using mMaxOf3 is " << long double mMaxOf3(primary, secondary, tertiary); return 0; } This is the error that I am getting. |20|error: expected unqualified-id before '{' token|

  Read the article

• Usage of CRTP in a call chain

  - by fhw72

  In my widget library I'd like to implement some kind of call chain to initialize a user supplied VIEW class which might(!) be derived from another class which adds some additional functionality like this: #include <iostream> template<typename VIEW> struct App { VIEW view; void init() {view.initialize(); } }; template<typename DERIVED> struct SpecializedView { void initialize() { std::cout << "SpecializedView" << std::endl; static_cast<DERIVED*>(this)->initialize(); } }; struct UserView : SpecializedView<UserView> { void initialize() {std::cout << "UserView" << std::endl; } }; int _tmain(int argc, _TCHAR* argv[]) { // Cannot be altered to: App<SpecializedView<UserView> > app; App<UserView> app; app.init(); return 0; } Is it possible to achieve some kind of call chain (if the user supplied VIEW class is derived from "SpecializedView") such that the output will be: console output: SpecializedView UserView Of course it would be easy to instantiate variable app with the type derived from but this code is hidden in the library and should not be alterable. In other words: The library code should only get the user derived type as parameter.

  Read the article

• write a program that prompts the user to input five decimal numbers : C++

  - by user312309

  This is the question. write a program that prompts the user to input five decimal numbers. the program should then add the five decimal numbers, convert the sum to the nearest integer,m and print the result. This is what I've gotten so far: // p111n9.cpp : Defines the entry point for the console application. // #include <iostream> using namespace std; double a, b , c , d , e, f; int main(int argc, char* argv[]) { cout << "enter 5 decimals: " << endl; cin >> a >> b >> c >> d >> e; f = a + b + c + d + e; return 0; } Now I just need to convert the sum(f) to the nearest integer, m and print the result. How do I do this?

  Read the article

• Dynamic function arguments in C++, possible?

  - by Jeshwanth Kumar N K

  I am little new to C++, I have one doubt in variable argument passing. As I mentioned in a sample code below ( This code won't work at all, just for others understanding of my question I framed it like this), I have two functions func with 1 parameter and 2 parameters(parameter overloading). I am calling the func from main, before that I am checking whether I needs to call 2 parameter or 1 parameter. Here is the problem, as I know I can call two fuctions in respective if elseif statements, but I am curious to know whether I can manage with only one function. (In below code I am passing string not int, as I mentioned before this is just for others understanding purpose. #include<iostream.h> #include <string> void func(int, int); void func(int); void main() { int a, b,in; cout << "Enter the 2 for 2 arg, 1 for 1 arg\n"; cin << in; if ( in == 2) { string pass = "a,b"; } elseif ( in == 1) { string pass = "a"; } else { return 0; } func(pass); cout<<"In main\n"<<endl; } void func(int iNum1) { cout<<"In func1 "<<iNum1<<endl; } void func(int iNum1, int iNum2) { cout<<"In func2 "<<iNum1<<" "<<iNum2<<endl; }

  Read the article

• Strange output produced by program

  - by Boom_mooB

  I think that my code works. However, it outputs 01111E5, or 17B879DD, or something like that. Can someone please tell me why. I am aware that I set the limit of P instead of 10,001. My code is like that because I start with 3, skipping the prime number 2. #include <iostream> bool prime (int i) { bool result = true; int isitprime = i; for(int j = 2; j < isitprime; j++) ///prime number tester { if(isitprime%j == 0) result = false; } return result; } int main (void) { using namespace std; int PrimeNumbers = 1; int x = 0; for (int i = 3 ; PrimeNumbers <=10000; i++) { if(prime(i)) { int prime = i; PrimeNumbers +=1; } } cout<<prime<<endl; system ("pause"); return 0; }

  Read the article

• Allocating 32-bit integer arrays in 64-bit machines

  - by Shredderroy

  I have a 64-bit i7 machine. Suppose I allocate memory for n 32-bit integers. How many physical registers will actually be used in the allocation: n, or n/2? I tried to write the following simple programme to find out. #include <iostream> #include <cstdlib> using namespace std; int main (int argc, char *argv[]) { int a[4]; cout << &a[0] << "\t" << &a[3] << endl; cin.ignore (1); return 0; } // End main () The output is: 0018FA04 0018FA10 They seem further apart than they should be. Why aren't the addresses 04 and 07? And does this mean that the system is actually allocating four (or more) integers, instead of packing the four 32-bit integers into two 64-bit registers? Thanks in advance for your help.

  Read the article

• error: 'void Base::output()' is protected within this context

  - by Bill

  I'm confused about the errors generated by the following code. In Derived::doStuff, I can access Base::output directly by calling it. Why can't I create a pointer to output() in the same context that I can call output()? (I thought protected / private governed whether you could use a name in a specific context, but apparently that is incomplete?) Is my fix of writing callback(this, &Derived::output); instead of callback(this, Base::output) the correct solution? #include <iostream> using std::cout; using std::endl; template <typename T, typename U> void callback(T obj, U func) { ((obj)->*(func))(); } class Base { protected: void output() { cout << "Base::output" << endl; } }; class Derived : public Base { public: void doStuff() { // call it directly: output(); Base::output(); // create a pointer to it: // void (Base::*basePointer)() = &Base::output; // error: 'void Base::output()' is protected within this context void (Derived::*derivedPointer)() = &Derived::output; // call a function passing the pointer: // callback(this, &Base::output); // error: 'void Base::output()' is protected within this context callback(this, &Derived::output); } }; int main() { Derived d; d.doStuff(); }

  Read the article

• Is there any way to output the actual array in c++

  - by user2511129

  So, I'm beginning C++, with a semi-adequate background of python. In python, you make a list/array like this: x = [1, 2, 3, 4, 5, 6, 7, 8, 9] Then, to print the list, with the square brackets included, all you do is: print x That would display this: [1, 2, 3, 4, 5, 6, 7, 8, 9] How would I do the exact same thing in c++, print the brackets and the elements, in an elegant/clean fashion? NOTE I don't want just the elements of the array, I want the whole array, like this: {1, 2, 3, 4, 5, 6, 7, 8, 9} When I use this code to try to print the array, this happens: input: #include <iostream> using namespace std; int main() { int anArray[9] = {1, 2, 3, 4, 5, 6, 7, 8, 9}; cout << anArray << endl; } The output is where in memory the array is stored in (I think this is so, correct me if I'm wrong): 0x28fedc As a sidenote, I don't know how to create an array with many different data types, such as integers, strings, and so on, so if someone can enlighten me, that'd be great! Thanks for answering my painstakingly obvious/noobish questions!

  Read the article

• array multiplication task

  - by toby

  I am tying to get around how you will multiply the values in 2 arrays (as an input) to get an output. The problem I have is the how to increment the loops to achieve the task shown below #include <iostream> using namespace std; main () { int* filter1, *signal,fsize1=0,fsize2=0,i=0; cout<<" enter size of filter and signal"<<endl; cin>> fsize1 >> fsize2; filter1= new int [fsize1]; signal= new int [fsize2]; cout<<" enter filter values"<<endl; for (i=0;i<fsize1;i++) cin>>filter1[i]; cout<<" enter signal values"<<endl; for (i=0;i<fsize2;i++) cin>>signal[i]; /* the two arrays should be filled by users but use the arrays below for test int array1[6]={2,4,6,7,8,9}; int array2[3]={1,2,3}; The output array should be array3[9]={1*2,(1*4+2*2),(1*6+2*4+3*2),........,(1*9+2*8+3*7),(2*9+3*8),3*9} */ return 0; } This is part of a bigger task concerning filter of a sampled signal but it is this multiplication that i cant get done.

  Read the article

• QMetaMethods for regular methods missing?

  - by oleks

  Hi, I'm new in QT, and I'm just testing out the MOC. For a given class: class Counter : public QObject { Q_OBJECT int m_value; public: Counter() {m_value = 0;} ~Counter() {} int value() {return m_value;} public slots: void setValue(int value); signals: void valueChanged(int newValue); }; I want to get a list of all methods in a class, but seem to only be getting a list of signals and slots, although the documentation says it should be all methods? Here's my code: #include <QCoreApplication> #include <QObject> #include <QMetaMethod> #include <iostream> using std::cout; using std::endl; int main(int argc, char *argv[]) { QCoreApplication app(argc, argv); const QMetaObject cntmo = Counter::staticMetaObject; for(int i = 0; i != cntmo.methodCount(); ++i) { QMetaMethod qmm(cntmo.method(i)); cout << qmm.signature() << endl; } return app.exec(); } Please beware this is my best c/p, perhaps I forgot to include some headers. My output: destroyed(QObject*) destroyed() deleteLater() _q_reregisterTimers(void*) valueChanged(int) setValue(int) Does anyone know why this is happening? Does qt not recognise int value() {return m_value;} as a valid method? If so, is there a macro I've forgotten or something like that? P.S. I'm using 4.6.2 UPDATE I forgot the implementation of the setValue method, not that it makes too much a difference to my actual question. void Counter::setValue(int value) { if(value != m_value) { m_value = value; emit valueChanged(value); } }

  Read the article

• format, iomanip, c++

  - by Crystal

  I'm trying to learn to use namespaces declarations more definitive than not just say "using namespace std". I'm trying to format my data to 2 decimal places, and set the format to be fixed and not scientific. This is my main file: #include <iostream> #include <iomanip> #include "SavingsAccount.h" using std::cout; using std::setprecision; using std::ios_base; int main() { SavingsAccount *saver1 = new SavingsAccount(2000.00); SavingsAccount *saver2 = new SavingsAccount(3000.00); SavingsAccount::modifyInterestRate(.03); saver1->calculateMonthlyInterest(); saver2->calculateMonthlyInterest(); cout << ios_base::fixed << "saver1\n" << "monthlyInterestRate: " << saver1->getMonthlyInterest() << '\n' << "savingsBalance: " << saver1->getSavingsBalance() << '\n'; cout << "saver2\n" << "monthlyInterestRate: " << saver2->getMonthlyInterest() << '\n' << "savingsBalance: " << saver2->getSavingsBalance() << '\n'; } On Visual Studio 2008, when I run my program, I get an output of "8192" before the data I want. Is there a reason for that? Also, I don't think I am setting the fixed part or 2 decimal places correctly since I seem to get scientific notation once I added the setprecision(2). Thanks.

  Read the article

< Previous Page | 22 23 24 25 26 27 28 29 30 31 32 33  | Next Page >