Recent questions tagged C++

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c++ - How do I convert wchar_t* to std::string?

I changed my class to use std::string (based on the answer I got here but a function I have returns ... std::basic_string<_Elem,_Traits,_Ax>' 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++ - Argument type auto deduction and anonymous lambda functions

Lets say I have these lines of code; std::vector<int> ints; std::for_each(ints.begin(), ints.end(), [](int& val){ ... ints)& val){ val = 7; }); 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 causes a Sigtrap in a Debug Session

In my c++ program I'm using a library which will "send?" a Sigtrap on a certain operations when I'm ... understand the background. Thanks a lot. 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++ - Qt - copy a file from one directory to another

I am using QT, I am not able to find out how to copy a file from one directory to another? How can I achieve 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++ - What's the difference between "= default" destructor and empty destructor?

I want to prevent the user of my class from using it as an automatic variable, so I write code like ... " destructor and an empty destructor? 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 causes a SIGABRT fault?

Could you please tell me what could possibly cause a SIGABRT fault in 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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c++ - How to store array in one column in Sqlite3?

Is there any way to store an array of integers in one column of table? I want o/p like this: ident | value | ... i am not sure how to do 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++ - In C++11 is sqrt defined as constexpr?

In C++11 is std::sqrt defined as constexpr, i.e. can it legally be used from other constexpr functions ... about sqrt or other math functions. 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++ - Read a text file line by line in Qt

How can I read a text file line by line in Qt? I'm looking for the Qt equivalent to: std::ifstream infile; std ... (infile, line)) { ... } 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++ - Use of string_view for map lookup

The following code fails to build on recent compilers (g++-5.3, clang++-3.7). #include <map> #include ... error happens with boost::string_ref. 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 consteval?

Apparently, consteval is going to be a keyword in C++20. The cppreference page for it is currently blank. What ... does it relate to constexpr? 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++ - vector::push_back vs vector::operator[]

Below in c++ program, include<iostream> #include<vector> using namespace std; int main() { vector<int> numbers; ... or something else is there? 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++ - Casting to void* and Back to Original_Data_Type*

I have seen and used this many times is C++, specially in various thread implementations. What I wonder is if ... there are any? 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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573 views

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c++ - enum type can not accept cin command

Look t this code plz: #include <iostream> using namespace std; int main() { enum object {s,k,g}; object o, ... so what is wrong with this 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++ - Can optimizations affect the ability to debug a VC++ app using its PDB?

In order to be able to properly debug release builds a PDB file is needed. Can the PDB file become less ... - but the question is 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++ - Trying to optimize line vs cylinder intersection

My brain has been melting over a line segment-vs-cylinder intersection routine I've been working on. /// Line segment VS ... .001 || ... 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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c++ - I'm using the SDL functions without the SDL_main be defined. Is that fine?

that's my code: Lib.h #ifdef ExportLib #define Lib __declspec(dllexport) #else #define Lib __declspec(dllimport) #endif ... I lost doing 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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175 views

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c++ - Reading data from Dukascopy tick binary file

I have downloaded the Dukascopy tick data and I have decompressing it with easylzma library. The original compressed ... file. Please help me. 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++ - build tuple using variadic templates

So I have some code written before C++11 that parses a string based on template arguments. Instead of having one ... could apply to this case. 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 do I link different versions of the same library in g++?

I'm trying to figure out how to load two different versions of libstdc++.so on a SLES10 machine. My client ... What should I be doing instead? See Question&Answers more detail:os...

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

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407 views

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c++ - how to get vendor id and product id of a plugged usb device on windows

I am using Qt on windows platform. i want to get and display vendor id and product id of a plugged usb device from ... } Any ideas in 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++ - Calculate the Fibonacci number (recursive approach) in compile time (constexpr) in C++11

I wrote the program Fibonacci number calculation in compile time (constexpr) problem using the template metaprogramming ... for both programs. 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++ - Class members and member functions memory location

Here be a simple C++ class: class A { public: explicit A() : m_a(0) { } explicit A(int a) m_a(a) { } ... out if what I know is right or 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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c++ - Generating a Deck of Cards

I'm trying to make a simple blackjack program. Sadly, I'm having problems right off the bat with generating a ... code. Thanks for your 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 detect the Sun from the space sky in OpenCv?

I need to detect the Sun from the space sky. These are examples of the input images: I've got such results ... worked with big number of tests. See Question&Answers more detail:os...

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

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526 views

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c++ - Building GMP library with Visual Studio?

Is there an easy way to build the GMP (GNU Multiple Precision Arithmetic Library, http://gmplib.org) under ... /www.holoborodko.com/pavel/mpfr/ See Question&Answers more detail:os...

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

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182 views

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c++ - Getting the type of a typename or expression

Consider the following example. Somewhere in my code is a name x. I have no idea if x is a type or an object ( ... y; How can I get this done? See Question&Answers more detail:os...

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

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129 views

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c++ - c++11: How to write a wrapper function to make `std::function` objects

I am trying to write a wrapper make_function, which like std::make_pair can create a std::function object out ... /overload2 return 0; } Ideone See Question&Answers more detail:os...

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

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