Recent questions tagged C++

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c++ - Is it bad practice for a child object to have a pointer to its parent?

In a C++ application, let's say I have a window class, which has several instances of a control class. ... to the vector would be infrequent). See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why is volatile keyword not needed for thread synchronisation?

I am reading that the volatile keyword is not suitable for thread synchronisation and in fact it is not needed for ... wrong in here. But why? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Private function member called outside of class

In the example below, why is B::f() called even though it is private? I know this fact that : Access is checked at the ... () { B b; C(b); } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to detect -stdlib=libc++ in the preprocessor?

I think this is part of the problem at No type named 'unique_ptr' in namespace 'std' when compiling ... other external libraries or frameworks. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Cast from unsigned long long to double and vice versa changes the value

When writing a C++ code I suddenly realised that my numbers are incorrectly casted from double to unsigned long long. ... == 8 for my system. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why isn't operator[] overloaded for lvalues and rvalues?

The standard C++ containers offer only one version of operator[] for containers like vector<T> and deque<T>. ... standard containers in C++14? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Disabling precompiled headers for a specific file in a VC++ 2010 project

As the title says. I have a C++ project, and added 1 C .h file and a C .c source file, but they ... .c source files) and disable PCH? Thanks. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - is `warning C4127` (conditional expression is constant) ever helpful?

While answering this post, I suggested using do {...} while(0) for multiline macros. On MSVC, I found ... warning ever help writing better code? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Should the name of my classes begin with 'Q' in Qt?

When I first started working with Qt, it was extremely annoying that every class has a name beginning with 'Q', ... beginning with 'Q'. Nice! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Multiple Inheritance: same variable name

class A { protected: string word; }; class B { protected: string word; }; class Derived: public A, public B ... Derived? How would I resolve it? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - What is a Delphi DCU file?

What is a Delphi DCU file? I believe it stands for "Delphi Compiled Unit". Am I correct in assuming it contains ... C/C++ source code file? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Is it possible to random_shuffle an array of int elements?

I was reading up on this : http://www.cplusplus.com/reference/algorithm/random_shuffle/ and wondered if its ... What does my error mean? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - g++ rejects, clang++ accepts: foo(x)("bar")("baz");

Somebody had asked the other day why something compiles with clang, but not with gcc. I intuitively understood what was ... .3, clang-3.5.1 See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - get<string> for variants fail under clang++ but not g++

The following code: variant<string> x = "abc"; cout << get<string>(x) << " "; works fine under g++ ( ... or is my code illegal in any way? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - emplace_back not working with std::vector<std::map<int, int>>

I am trying to do emplace_back into a std::vector<std::map<int, int>>, but could not find the right ... How can I get emplace_back working? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Designated initializers in C++20

I've got a question about one of the c++20 feature, designated initializers (more info about this feature ... Could someone explain me why ? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ cli - How to associate constants with an interface in C#?

Some languages let you associate a constant with an interface: A Java example A PhP example The W3C abstract ... associated with an interface? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Using a variable with the same name in different spaces

This code compiles, but I have a run time error in Visual Studio: Run-time check failure #3 - the variable 'x' is being ... ,2,3,4}; return 0; } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Output ASCII value of character

#include <iostream> using namespace std; int main() { char x; cout << "enter a character:"; cin >> x; cout ... : 2 errors, 0 warnings ===| See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Finding whether a number has P^Q form or not?

I have recently appeared online coding Test. I was struck one question i.e A number N is given finding the ... : yes Constraints: 2<N<100000 See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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626 views

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c++ - Macro in class definition

class is defined using Macro. Not sure what is the significance of MACRO DEBUG_API here. [I understand #define is used ... methods here. */ }; See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Delete and invalid pointer

int main() { char* a=new char[20]; cin>>a; cout<<" character at 7-th position."<<a[6]; delete a ... case how come all the elements are deleted? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Store details of a binary image consisting simple polygons

This question relates to somewhat practice and experienced based process. I have an Mat binary image which ... efficiency of the program. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - C++20 std::atomic<float>- std::atomic<double>.specializations

C++20 includes specializations for atomic<float> and atomic<double>. Can anyone here explain for what practical purpose ... the C++20 standard. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - R G B element array swap

I'm trying to create this c++ program to perform the description below. I am pretty certain the issue is in the ... << endl; pca++; } } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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476 views

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c++ - Plot Spectrum in real time?

I would like to add and plot the spectrum of signal on Qwt Oscillocope's example. My Idea is to create ... Advice would be appreciated. Thanks See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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565 views

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c++ - Pass tuple's content as variadic function arguments

I play with C++0x for some time and now I want to use variadic templates and tuple to implement class "Task". ... way to solve my problem... See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Error with passing a pointer using threads

Updated code: 3/7/11 : 9:29pm using namespace std; void * matrixACreate(void * param); void *status; struct a { ... >Arow << endl; return 0; } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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