Recent questions tagged C++

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Intro I'm looking for a pattern to convert C++ type traits into their variadic counterparts. A methodology to ... number of type arguments ? 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 can't you do bitwise operations on pointer in C, and is there a way around this?

I read that you can't do bitmasks on pointers, how come you can't do bitwise operations on pointers? Is there any ... the same apply to 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++ - The amortized complexity of std::next_permutation?

I just read this other question about the complexity of next_permutation and while I'm satisfied with the response ( ... of such an analysis? 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++03. Test for rvalue-vs-lvalue at compile-time, not just at runtime

In C++03, Boost's Foreach, using this interesting technique, can detect at run-time whether an expression is ... -versus-rvalue at runtime.) 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 are not all Boost libraries header-only?

Why are all libraries in Boost not headers-only? Saying it differently, what makes the use of .lib/.dll ... template or has static fields? 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++ - Is Type(::x); valid?

While discussing the Type(identifier); syntax and how it's a declaration, I came across Type(::x); not working ... Is this code valid or 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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c++ - How to Apply Mask to Image in OpenCV?

I want to apply a binary mask to a color image. Please provide a basic code example with proper explanation ... operate only within the mask? 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 base class destructor if a derived class destructor throws an exception

It just happened to me I wondered how resources are freed in the following case. class Base { Resource *r; public: ... Or will there be a leak? 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++ - Iterating through a vector of pointers

I'm trying to iterate through a Players hand of cards. #include <vector> #include <iostream> class Card { int ... . How can I fix 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++ - C++11 lambdas can access my private members. Why?

Consider this piece of code: class shy { private: int dont_touch; // Private member public: static const shy object; ... this a GCC/Clang bug? 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++ - Time complexity of find() in std::map?

How efficient is the find() function on the std::map class? Does it iterate through all the elements looking for ... a hash function or what? 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 is snprintf faster than ostringstream or is it?

I read somewhere that snprintf is faster than ostringstream. Has anyone has any experiences with it? If yes why is it faster. 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++ - Name resolution for recursive trailing return type

I found a weird difference between explicit and automatic trailing return types. In the following code, we define a ... for the name lookup? 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 a value of an enum with a fixed underlying type of char resolve to fct(int) instead of fct(char)?

This problem came up when answering this question about overload resolution with enums. While the case for long long ... I see mandates 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++ - A value of type "const char*" cannot be used to initialize an entity of type "char *"

I have a code like this but I keep receiving this error : A value of type "const char*" cannot be ... I am using Visual Studio Community 2017 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 assert() without using abort()?

If I use assert() and the assertion fails then assert() will call abort(), ending the running program ... chance to handle them gracefully? 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++ - Get member of __m128 by index?

I've got some code, originally given to me by someone working with MSVC, and I'm trying to get it to work ... 't yet found an appropriate one. 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++ - Is it possible to map string to int faster than using hashmap?

I understand that I should not optimize every single spot of my program so please consider this question to be ... 20-charachters long tickers. 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 Execute external program

I want to start an external program out of my QT-Programm. The only working solution was: system("start ... But nothing happened. 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++ - Optimizing very often used anagram function

I have written a function that determines whether two words are anagrams. Word A is an anagram of word B if ... how to speed this function up? 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: "dependent name is not a type". When use typedef type in class as return value, with template

template <class Item> class bag { public: //TYPEDEF typedef size_t size_type; typedef Item value_type; ... } ... anybody show me why? 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++ - Is a class with deleted copy-constructor trivially copyable?

Is this class: class A { public: A() = default; A(const A&) = delete; }; trivially copyable? (At least ... proven wrong] plus its comment tree. 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++ - Static variable inside template function

In C++, if you define this function in header.hpp void incAndShow() { static int myStaticVar = 0; std: ... my implementation that is doing 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++ - Constructor conditionally marked explicit

Update: conditional explicit has made it into the C++20 draft. more on cppreference The cppreference std::tuple constructor ... S(T t) {} 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 if a pointer was deleted and securely delete it?

In C++ How to decide or know if a pointer was deleted before?? when i tried to delete a pointer that was ... given was - Never use raw pointers. 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++ - CMake on Windows

I am trying to run CMake on Windows, and I get the following error: -- The C compiler ... C:Anaconda2MinGWx86_64-w64-mingw32ingcc.exe 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 LNK2005: _DllMain@12 already defined in MSVCRT.lib

I am getting this linker error. mfcs80.lib(dllmodul.obj) : error LNK2005: _DllMain@12 already defined in MSVCRT. ... VS 2005 with Platform SDK 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++ - String representation of time_t?

time_t seconds; time(&seconds); cout << seconds << endl; This gives me a timestamp. How can I get that epoch ... s = seconds; does 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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