Recent questions tagged C++

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c++ - What is the difference between string::at and string::operator[]?

I was taught string::at in school, but by exploring the string library I saw string::operator[], which I was ... differences I'm not aware of? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Can we omit the double-braces for std::array in C++14?

I'm reading through the draft standard for C++14 right now, and perhaps my legalese is a bit rusty, but I can't find any ... }}, {{ 3, 4 }} }; See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Different compiler behavior for expression: auto p {make_pointer()};

Which is the correct behaviour for the following program? // example.cpp #include <iostream> #include <memory> struct ... example.cpp (code 2) See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - When can we omit the return type in a C++11 lambda?

As far as I know, in standard C++11 (not C++14), when omitting the return type of a lambda, its ... here? Am I interpreting the standard wrong? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - What happens when a function that returns an object ends without a return statement

In C++, what happens when a function that is supposed to return an object ends without a return statement? What gets ... . std::string func() {} See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why are the return values of these doubles -1.#IND?

I have : double score = cvMatchContourTrees( CT1, CT2, CV_CONTOUR_TREES_MATCH_I1, 0.0 ); cout<<score<<endl; There are ... ? How do I solve it? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Where should non-member operator overloads be placed?

I want to overload operator<< for my class. Should I add this overloaded definition to the std namespace? ( ... in advance for your responses. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Constructor of type int

Considering the cost, are these cases the same? // case 1 int a = 5; // case 2 int a (5); // case 3 int a; a = 5 See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to convert Platform::String to char*?

How do I convert the contents of a Platform::String to be used by functions that expect a char* based string? ... just can't find them. Thanks! See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why must initializer list order match member declaration order?

Why does gcc throw a hissy fit if the initializer list order doesn't match variable order in the class? class ... where it may backfire maybe?) See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Initializer-list-constructing a vector of noncopyable (but movable) objects

One can push_back rvalues of a noncopyable-but-movable type into a vector of that type: #include <vector> struct S ... handy at the moment... See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why "not all control paths return a value" is warning and not an error?

I was trying to answer this question. As suggested by the accepted answer, the problem with that code is ... dreaded undefined behavior again? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Delete calling destructor but not deleting object?

So I have been working with c++ and pointers for a year and a half now, and i thought i had them succeed. I ... for it not to give me the error? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - ReleaseSemaphore does not release the semaphore

(In short: main()'s WaitForSingleObject hangs in the program below). I'm trying to write a piece of code that ... Done "); getc(stdin); } See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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508 views

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c++ - parsing complete messages from serial port

I am trying to read complete messages from my GPS via serial port. The message I am looking for starts with: ... can also read in the length See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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687 views

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c++ - OpenCV on ubuntu 11.10

I've just updated my system from ubuntu 11.04 to 11.10 and now I can't compile anymore any C program that ... lm hello.c Anyone can help me? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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625 views

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c++ - Disabling TDR for CUDA in Windows 8

I recently found this article for C++AMP where you can temporaly disable TDR in Windows 8. Is there any way to apply this solution for CUDA? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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575 views

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c++ - Why does sizeof(int) vary across different operating systems?

I wounder why size of int depends on which OS one is using ,in C & C++. It's ok if size of pointer varies, ... (int) = 4 byte. Why so? Thanks. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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780 views

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c++ - OpenCV on Mac is not opening USB web camera

I have been unsuccessful using OpenCV's VideoCapture.open(int) to get video capture from a USB web cam in my ... How can I fix this problem? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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778 views

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c++ - How to pause a pthread ANY TIME I want?

recently I set out to port ucos-ii to Ubuntu PC. As we know, it's not possible to simulate the "process" ... the older solution. Thanks a lot. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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832 views

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c++ - writing a matrix into a single txt file with mpi

I have a huge matrix that I divided it into some sub matrices and I make some computation on it. After those ... matrix into a single text file. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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859 views

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c++ - cmake - Global linker flag setting (for all targets in directory)

I want to pass linker flags to all sub-projects (sub-directory CMakeList) in my project. Before ... Makefiles" -DCMAKE_BUILD_TYPE=Release . See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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569 views

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c++ - Does boost::bind() copy parameters by reference or by value?

Why does valgrind's DRD tool complaines "Conflicting load by thread ... at size 4": about such code: void ... values by reference or value? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Qt macro keywords cause name collisions

I am building an NCurses interface for my Qt project. I want to use CDK but I think the signals member of this ... I get CDK to work with Qt? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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727 views

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c++ - Mutually recursive classes

How do I implement mutually recursive classes in C++? Something like: /* * Recursion.h * */ #ifndef RECURSION_H_ ... ; #endif /* RECURSION_H_ */ See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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541 views

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c++ - Copy constructor vs. return value optimization

In a previous question, it appeared that a plain return-by-value function always copies its return argument into the variable ... f( 1, 2 ); } See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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584 views

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c++ - Why does sqrt() work fine on an int variable if it is not defined for an int?

In chapter 3 of Programming: Principles and Practice using C++ (sixth printing), Stroustrup states (p.68): ... the program above fail somehow? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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615 views

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c++ - Why does cin command leaves a ' ' in the buffer?

This is related to: cin and getline skipping input But they don't answer the why it happens just the how to ... but it does with cin.getline? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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