Recent questions tagged C++

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c++ - `auto` return type in context of class members

How can automatic type deduction be used for class members? For example, the following code struct A { auto ... and definition is separated. 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++ - Mapping array back to an existing Eigen matrix

I want to map an array of double to an existing MatrixXd structure. So far I've managed to map the Eigen ... back to the existing matrix } 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++ - Strange behavior of copy-initialization, doesn't call the copy-constructor!

I was reading the difference between direct-initialization and copy-initialization (§8.5/12): T x(a); //direct ... the behavior 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++ - How to map a bool to a 3d point struct with std::map?

How do I use the following struct: struct point { int x; int y; int z; }; as a key for std::map< ... should I define operator< for two points? 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 a Specific Digit of a Number

I'm trying to find the nth digit of an integer of an arbitrary length. I was going to convert the integer to ... any other way to do this? 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 2.3: Convert Mat to RGBA pixel array

I am attempting to use OpenCV to grab frames from a webcam and display them in a window using SFML. VideoCapture ... other than BGR. Any ideas? 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++ - Boost.Asio SSL thread safety

Do I create one strand that all of my SSL sockets share, or one strand per SSL context (shared ... in case that matters. 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++ - Create n-dimensional vector with given sizes

So, what I want is to create multidimensional vector of given type where the first dimension will have size of the ... . How do I fix that? 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++ - Protecting QML source code from plagiarism

The goal is to come up with a way to protect your QML code from plagiarism. It is a problem, since ... sources and referencing each other. 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++ - Effect of noskipws on cin>>

As I understand, the extraction operator skips the whitespace in the beginning and stops upon encountering a whitespace ... entered 0 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++ - What's the difference between boost::io_service poll_one and run_one?

io_service::poll_one Run the io_service object's event processing loop to execute one ready handler. vs io_service:: ... ASIO is very sparse. 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++ - CGAL 2D Delaunay Triangulation: How to get edges as vertex id pairs

I have a set of 2D points each with an associated id. (e.g. if the points are stored in an array, the id is ... .finite_edges_end(); ++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++ - When enabling C++11 with stdlibc++ 4.7, clang error out, while gcc compiles fine

I have been trying to get C++11 to work, after browsing different websites and Q/A, i am still having trouble ... with latest gcc 4.7 libstc++? 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++ - -O1/2/3 with -std=c++1y/11/98 - If <cmath> is included i'm getting error: '_hypot' was not declared in this scope

I've just updated MinGW using mingw-get-setup and i'm unable to build anyting that contains <cmath> header if ... any quick fix for this header? 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 I assume allocators don't hold their memory pool directly (and can therefore be copied)?

I'm writing a container and would like to permit the user to use custom allocators, but I can't tell if I ... I can rely on this assumption.) See Question&Answers more detail:os...

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

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408 views

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c++ - freopen: reverting back to original stream

I needed to forward stdout to different files to separate some prints produced and the reverting back to normal ... do? Thanks in advance See Question&Answers more detail:os...

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

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325 views

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c++ - Visual Studio 2015 - Compiler Warning (level 2) C4146

I have the following line in my code signed int test_case= -2147483648; which generates the error: C4146 unary ... "signed" assignment? 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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211 views

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c++ - gcc vs clang: inlining a function with -fPIC

Consider this code: // foo.cxx int last; int next() { return ++last; } int index(int scale) { return next() ... , or is this purely a QoI issue? 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 happens to the return value if I don't store it anywhere?

In the small sample below: #include<iostream> using namespace std; int z(){ return 5 + 10; // returns 15 } ... debugger I see that it is not. See Question&Answers more detail:os...

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

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252 views

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c++ - Do I need to delete a pointer if I haven't assigned it a new value?

Just a quick question: Do I need to delete a pointer if I haven't actually assigned a new value to it? What I've ... can I just set it to null? See Question&Answers more detail:os...

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

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189 views

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c++ - Why does std::remove not work with std::set?

The following code: #include <iostream> #include <set> #include <algorithm> std::set<int> s; int main() { s. ... (pretty simple) code not work? See Question&Answers more detail:os...

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

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153 views

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c++ - Any program or trick to find the definition of a variable?

Many times when I am watching others code I just want to find where and how a variable is defined. Normally ... the locality of the variable. See Question&Answers more detail:os...

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

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117 views

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c++ - Why is my program so slow?

Someone decided to do a quick test to see how native client compared to javascript in terms of speed. They ... the native client mailing list See Question&Answers more detail:os...

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

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218 views

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c++ - Will there be standardization of scope guard/scope exit idioms?

Running a lambda on scope exit seems like such a basic thing, I would expect it to be standardized. Things like ... know if this is coming? See Question&Answers more detail:os...

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

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610 views

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c++ - Libusb undefined reference to

I'm trying to set up libusb API on my OS. I downloaded libusb api on libusb.org. I followed the standard ... Thanks very much for 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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532 views

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c++ - C++11: template parameter redefines default argument

When compiling the following source code with gcc there are no errors / warnings: template< typename T = int > T ... point in the C++ 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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328 views

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c++ - detecting end of input with cin

I want to read a line of integers from the user. I'm not sure how to check to see if the input has ended. ... there's any more for cin to take? See Question&Answers more detail:os...

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

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338 views

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c++ - QT: socket notifiers cannot be enabled from another thread

I have a QTcpSocket and I need to control it - write + read using multiple threads. This works fine in QT4 but ... to use it from both threads. See Question&Answers more detail:os...

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

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