Recent questions tagged C++

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c++ - How to set non-selectable default text on QComboBox?

Using a regular QComboBox populated with items, if currentIndex is set to -1, the widget is empty. It ... any previous questions with answers. 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 find the width of a String (in pixels) in WIN32

Can you measure the width of a string more exactly in WIN32 than using the GetTextMetrics function and using tmAveCharWidth*strSize? 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++ - Vector vs string

What is the fundamental difference, if any, between a C++ std::vector and std::basic_string? 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++ - boost::variant - why is "const char*" converted to "bool"?

I have declared a boost::variant which accepts three types: string, bool and int. The following code is showing ... to string a higher priority? 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++ - Passing int&& to f(int&&)

What is exactly happening here? Why is this an error? void f(int &&); int && i = 5; f(i); Isn ... is not an rvalue reference after declaration? 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 reuse stringstream

These threads do NOT answer me: resetting a stringstream How do you clear a stringstream variable? std:: ... szLine); szBuffer>>szKeyWord; 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 32 bit and 64 bit work together?

Can 64 bit library work in a 32 bit application? For example, my application GUI uses 32 bit Qt. And my ... they work together and how? 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++ - "g++" is not recognized as an internal or external command, MinGW

On my computer I have Windows 7 x86. I installed MinGW, I wrote the path but when I go in cmd.exe and write ... (I saw it must be installed). 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++ - Engineered bool compares equal to both true and false, why?

The example bellows compiles, but the output is rather strange : #include <iostream> #include <cstring> struct A { int a; ... am using g++ 4.3.0 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++ - Partial specialization of a method in a templated class

Given: struct A { virtual bool what() = 0; }; template<typename T, typename Q> struct B : public A { ... on a user defined type, not float. 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++ - Is there a way to check if an istream was opened in binary mode?

I'm using an istream which could be stringstream, ifstream or a user-defined stream type and I need to know ... stream was opened in text mode? 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++ - Calling a const function from a non-const object

I need to call a const function from a non-const object. See example struct IProcess { virtual bool doSomeWork() ... time. Please keep on topic. 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++ - Build project with "experimental/filesystem" using cmake

I need to add a "experimental/filesystem" header to my project #include <experimental/filesystem> int main() { auto ... .a Where is my mistake? 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++ - const T{}; works, const T; fails when T is a non-POD,

To start with, I have a struct with one value with a default value struct S { int a = 1; }; This type can ... type is not a POD or an aggregate? 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 increase error limit in Visual Studio?

When building an application in Visual Studio. It shows the following error when exceeding the error count fatal ... increase the error limit? See Question&Answers more detail:os...

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

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220 views

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c++ - Why can't I increment a variable of an enumerated type?

I have a enumerated type StackID, and I am using the enumeration to refer to an index of a particular vector ... want to link to this question. 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++ - Undefined reference error for static constexpr member

Consider this code: #include <vector> struct A { static constexpr int kDefaultValue = -1; std::vector<int> v; A ... another way to make it link? 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++ - Is there any technical reason why std::lower_bound is not specialized for red-black tree iterators?

I have always assumed that std::lower_bound() runs in logarithmic time if I pass a pair of red-black tree ... and accepting Yakk's answer. 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 get the current time zone?

In most of the examples I had seen: time_zone_ptr zone( new posix_time_zone("MST-07") ); But I just want to ... hard code the time zone name. 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++ - Difference between regex_match and regex_search?

I was experimenting with regular expression in trying to make an answer to this question, and found that while regex_match ... in GCC 4.7.1? See Question&Answers more detail:os...

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

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266 views

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c++ - Performance 32 bit vs. 64 bit arithmetic

Are native 64 bit integer arithmetic instructions slower than their 32 bit counter parts (on x86_64 machine with 64 bit ... Duo, i5/i7 etc. See Question&Answers more detail:os...

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

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264 views

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c++ - Proper way (move semantics) to return a std::vector from function calling in C++11

I want to fill std::vector (or some other STL container): class Foo { public: Foo(int _n, const ... redundant copying and constructor calls? See Question&Answers more detail:os...

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

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286 views

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c++ - Could not load Spatialite extension in qSqlite ( QT 5.9)

I am trying to load Spatialite as extension in qSqlite ( Qt 5.9), I have done that before with Qt4.8, ... about this problem? Thanks in advance. 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++ - Loop every 10 second

How to load a loop every 10 second and add +1 to the count and print it? like: int count; while(true) { ... know how, please help me out guys See Question&Answers more detail:os...

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

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299 views

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c++ - Simulating key press with PostMessage only works in some applications?

My approach to this problem turned out to be correct only in several programs. Why it isn't universal? Works ... this, nothing has changed. See Question&Answers more detail:os...

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

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167 views

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c++ - Using boost parse datetime string: With single digit hour format

I am working on code which needs to compile on NDK toolchain. Unfortunately, latest version only supports till ... help will be appreciated. See Question&Answers more detail:os...

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

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191 views

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c++ - How to stop TensorFlow from multi-threading

I am writing code for NIST FRVT. NIST wants the program to run at max 2 threads(Only CPU, No GPU). I am using TensorFlow ... .8.5 g++ -std=c++11 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++ - Static and global variable in memory

Are static variables stored on the stack itself similar to globals? If so, how are they protected to ... multi process/ thread enviornment? See Question&Answers more detail:os...

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

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