Recent questions tagged C++

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c++ - CUDA: Thread ID assignment in 2D grid

Let's suppose I have a kernel call with a 2D grid, like so: dim3 dimGrid(x, y); // not important ... any detailed information on this yet.. 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++ - Strlen returns unreasonable number

If I write: char lili [3]; cout<<strlen(lili)<<endl; then what is printed is : 11 but if I write: char ... , since I allocated 3 chars for lili? 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++ - Redirecting std::cout from DLL in a separate thread to QTextEdit

The goal is to display all the application output shown in QtCreator to a QTextEdit as a debug console window ... github.com/kuwt/ToyProject.git 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++ - cv::mean for non black pixel

I want to perform cv::mean on a cv::mat on non-black pixel. It's easy to do it using masking like ... exactly; no rounding should be happening. 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++ - Qualified friend function template instantiation

Looking at C++ Templates: The Complete Guide (2nd Edition)/official site this morning I came across a section I ... one in the same class. 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++ - Eigen Indices of Dense Matrix meeting Condition

I'm looking to get the row/column indices from a dense matrix which meet a condition. In my case the ... comparisons. Thanks for any help 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 paint / deform a QImage in 2D?

I have a code that manipulates and renders a QImage onto a QWidget. Manipulation includes typical homogeneous ... tool in PhotoShop? 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 linking Boost with CMake

I am using CLion on OS X 10.10.5 (Yosemite) and trying to use the logging boost (1.58.0) library. I ... does not seem to be an issue anymore. 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++ - Templated requires-expression

I want a Functor concept in C++20. A functor is a higher-kinded type that can be mapped over. A simple ... Could it make it into the 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++ - OpenCV waitKey() should return -1 but didn't

In the doc it says that It returns the code of the pressed key or -1 if no key was pressed before the specified time ... << c << std::endl; } 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 in g++10: generator not defined

This MCVE works fine in Visual Studio. #include <experimental/generator> #include <iostream> std::experimental:: ... that uses co_yield? 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 read XML using boost xml parser and store in map

As an example I am using the XML file listed here: https://msdn.microsoft.com/en-us/library/ms256129(v=vs.110).aspx ... ] = tagvalue; } } } } 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++ garbage values in vector of pointer

When I do: for(i=0; i<size; i++){ //create objectA here vectorA.push_back(objectA); pvectorA.push_back(&vectorA[ ... is okay. Why is it happens? 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++ - Getting a window's pixel format

I have created an OpenGL application running on Windows. Is there any way I can query information about the pixel ... Depth bits Pixel type etc. See Question&Answers more detail:os...

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

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738 views

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c++ - Undefined symbols in Crypto++/iOS 64-bit project

I tried to build with github's prebuilt cryptopp but it doesn't work, too. it occur errors like below: ... member function has no definition. 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++ - Can't access members of a Template base class within a derived template class

I have a template base class.Lets say. template<class KeyF> class Base { private: int member1; char member2; .. ... can't it access its member? 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 the common idiom for resizing a widget with a large image in Qt?

This may look like premature optimization, but I want to understand what happens on the inside and how this is ... to understand how this works. See Question&Answers more detail:os...

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

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994 views

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c++ - Qt Painter outside paintEvent - impossible - workaround?

So it appears that Qt4 doesn't let you draw on windows outside of a paint event. I have a lot of code that ... says it doesn't work on Windows. 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++ - If I make a piece of code in which each thread modifies completely different parts of an array, will that maintain cache coherency?

So I am making some parallel code using OpenMP (but this question should be reasonably applicable to other frameworks), ... be sure. Thank you. See Question&Answers more detail:os...

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

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682 views

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c++ - Calculate (a^b)%c where 0<=a,b,c<=10^18

How can I calculate (a ^ b) % c, where 0 <= a, b, c <= 10^18. Here, (a ^ b) ... = 123456789012345 the expected output should be: 59212459031520 See Question&Answers more detail:os...

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

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721 views

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c++ cli - C++/CLI: how to overload an operator to accept reference types?

I am trying to create a CLI value class c_Location with overloaded operators, but I think I have an issue with ... one? I currently prefer #2. See Question&Answers more detail:os...

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

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702 views

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c++ - Implementing B=f(A), with B and A arrays and B already defined

Suppose I have an array B that has been already defined and used somewhere in a C++ code. Now, suppose ... the answers kindly provided below. 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 do I get a 'ÿ' char after every include that is extracted by my parser? - C

I have this function: /*This func runs *.c1 file, and replace every include file with its content It will save ... extracted. Can't find 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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775 views

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c++ - Converting an iterative function to recursive

I know people usually ask this question the other way round, but I have the following problem: I have this iterative ... >next; } return c; } See Question&Answers more detail:os...

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

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836 views

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c++ - Can double pointers be used as 2D arrays

Suppose I have a 2D array - int Array[2][2]; I know that I can implement an array having 4 elements with 2 ... can be used as a 2D array. See Question&Answers more detail:os...

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

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826 views

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c++ - C++same class as member in class

I have a class that should have a class of the same type as its member. My declaration is the following: class ... 't know where I went wrong. See Question&Answers more detail:os...

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

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888 views

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c++ - Vector and []-operator overloading

I have inherited my class from std::vector. Now I want to overload the []-operator. When I try to ... required as left operand of assignment See Question&Answers more detail:os...

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

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1.1k views

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c++ - Win32 WndProc as class member

Is there a way to wrap WndProc as private member? If I have this: class Window { public: Window(); virtual ~ ... 0. How can this be fixed? See Question&Answers more detail:os...

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

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