Recent questions tagged c++

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c++ - How to convert signal name (string) to signal code?

I am writing a program that reads the name of the signal (e.g. SIGSTOP, SIGKILL etc) as a string from the ... more elegant way, if it exists. 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++ - Unsigned long and bit shifting

I have a problem with bit shifting and unsigned longs. Here's my test code: char header[4]; header[0] ... the correct value. 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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c++ - Problem adding std::filesystem to CMake Project

I am new to CMake projects and I want to use the file system library in my project. I am running Ubuntu ... answer as well. Thanks everyone! 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: invalid initialization of non-const reference of type ‘bool&’ from an rvalue of type ‘std::vector<bool>::reference {aka std::_Bit_reference}’

Why do I get the error: invalid initialization of non-const reference of type bool&' from an rvalue of type std:: ... I do to make it 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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c++ - Image of HSV color wheel for openCV?

I have written the code for histogram and i want to use it for SVM traning. But the fundamental problem is that i don' ... opencv (i.e. 0-180 ) 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++ - Declaring an array inside a class, and setting its size with the constructor

I haven't worked with c++ in a while, but I just started a project with it. This may not be possible ... particular build. 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++ - Scope resolution operator on enums a compiler-specific extension?

On this question, there's an answer that states: You can use typedef to make Colour enumeration type accessible without ... m not certain of 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++ - Why does gcc warn about calling a non-trivial move assignment operator with std::tuple and virtual inheritance?

In the following example gcc 7 gives a warning: defaulted move assignment for 'B' calls a non-trivial move ... to keep such a hierarchy? 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 doesn't std::string take a null pointer?

I recently passed a null pointer to a std::string constructor and got undefined behavior. I'm certain this is ... ::string(NULL) undefined is? 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++ - Thread-safe lock-free array

I have a C++ library, which supposed to do some computations on multiple threads. I made independent threads code ... 4.7 compiler 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++ - Opencv Error: no GPU support (library is compiled without CUDA support)

I am trying to work some image-process tasks with opencv on GPU with CUDA. I am using ubuntu. I setup my two ... opencv, but I still get 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++ - How to find rank of an element in stl set in O(logn)

I want to find rank of an element in stl set. I am able to traverse from beginning to that element and find out ... find the rank in O(logn). 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++ - `std::any_cast` returns a copy

I was reading the documentation for std::any_cast and I find it strange that the API has the cast either ... com/w/cpp/utility/any/any_cast 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++ - Fclose a file that is already fclose

In my programm I may close a file that is already close. What happen when I do a fclose on a file already close ... a file is closed or open ? 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 can I cleanly specify which arguments I am passing and which remain default?

Asked because of this: Default argument in c++ Say I have a function such as this: void f(int p1=1, int p2= ... there a better 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++ - How to add a library include path for NetBeans and gcc on Windows?

How to add a library include path for NetBeans and gcc on Windows? Using: NetBeans 7.1.2 MinGW (mingw-get-inst-20120426.exe) gcc 4.7.0 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++ - Concept difference between pre and post increment operator for STL

Supposedly: for (vector<int>::iterator iter = ivec.begin(); iter != ivec.end(); ++iter) {} I do ... that both yield the same result 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++ - Constant value in conditional expression

In a coding style question about infinite loops, some people mentioned they prefer the for(;;) style because the ... not be enabled in general? 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++ - Does POSIX regex.h provide unicode or basically non-ascii characters?

Hi i am using Standard Regex Library (regcomp, regexec..). But now on demand i should add unicode support to ... Any help would be appreciated.. See Question&Answers more detail:os...

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

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894 views

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c++ - How to change QPushButton icon using stylesheets in Qt app

Is it possible to set and change the icon on a QPushButton using stylesheets? I need this for a Windows- ... stylize using stylesheets. 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++ - Template detects if T is pointer or class

Considering the following code: class MyClass { ... }; template <typename Object> class List { public: void insert( ... to fix the code above? 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++ - Reference to Function syntax - with and without &

What's the difference between typedef void (&FunctionTypeR)(); vs typedef void (FunctionType)(); Is the second also ... ) when foo is invoked? 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++ - Bidirectional iterators in unordered_map?

The following minimal example: #include <iostream> #include <boost/unordered_map.hpp> int main() { boost::unordered_map<int, ... 0 and 1.43.0.) 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++ - Why does the performance of this non-matching pattern scale with the size of the search space?

I have code like the following: #include <regex> int main() { char buf[35000] = {}; auto begin = std:: ... I can work up the motivation. :) 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++ - constexpr object with mutable member

I came up with this class: class Point { public: int X, Y; mutable int Z; constexpr Point(int x, int y) ... can it call a non-constexpr method? 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++ - Abstract functions and variable arguments list

I have an abstract class an I like to know if it's possible to define an abstract function with variable ... example if it's possible. 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++ - conditional (SFINAE) override

I'm trying to do this: struct A { virtual int f() const { return 0; } }; template <typename T> struct B : A ... :f() override the member A::f()? 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++ - Android NDK Mutex

I am trying to do some multithreading using the Android Native Development Kit, so I need a mutex on the C++ ... use a mutex with Android NDK? See Question&Answers more detail:os...

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

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