Recent questions tagged C++

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c++ - How to select iterator type using auto variable?

I have a std::unordered_map std::unordered_map<std::string, std::string> myMap; I want to get a const iterator ... can force it to choose const? 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++ - Using a template before it's specialized?

I found out that you can specialize a template after it's first use if you use it using a wrapper template. ... T = S]' after instantiation 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 Boost.Serialization serialize differently on different platforms?

I use Boost.Serialization to serialize a std::map. The code looks like this void Dictionary::serialize(std:: ... signature exception if I try. 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++ - Compress 21 Alphanumeric Characters in to 16 Bytes

I'm trying to take 21 bytes of data which uniquely identifies a trade and store it in a 16 byte char array ... codes 32 through 125, inclusive. 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 profile a MEX-function in Matlab

I have a Mex-function (a function in c++ that you can call from Matlab) that I have written, and I want ... calling the c++ program from Matlab? 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++ continue versus break

Which statement will be executed after "continue" or "break" ? for(int i = 0; i < count; ++i) { // ... if(someTest) break; } //statement3 } 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++ - Compile error "'struct' type redefinition" although it's the first definition for it

Everything was working well untill I moved some code from the main file to a new class, then I had the following error ... , blue; }; Any idea ? 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++ - Shift masked bits to the lsb

When you and some data with a mask you get some result which is of the same size as the data/mask. What ... incredible image made in MS Paint. 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: cannot bind ‘std::basic_ostream<char>’ lvalue to ‘std::basic_ostream<char>&&’

I have already looked at a couple questions on this, specifically Overloading operator<<: cannot bind lvalue to std:: ... the end of my goal. 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++ - Do section numbers differ between the C++11 standard and the gratis draft N3337?

Does the numbering of clauses, sections, subsections, paragraphs, etc., differ between the C++11 standard ISO/ ... question with answers 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++ - inline static member variable

struct sa { struct sb { int a = 123;}; inline static sb b; }; The above code generates an error: main ... 't understand why this usage is 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++ - Is there a need to destroy char * = "string" or char * = new char[6]?

I assume that char* = "string" is the same to char* = new char[6]. I believe these strings are created ... do they get destroyed by themselves? 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++ - Include <string> not found compile error in Xcode 4.2

I'm getting include not found compile error in XCode. I have an iOS app project that i use Objective-c and ... type. Thanks much for 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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328 views

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c++ - Why is comparing against "end()" iterator legal?

According to C++ standard (3.7.3.2/4) using (not only dereferencing, but also copying, casting, whatever ... Is such comparison legal and why? 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 std::async copy its const & arguments?

I'm trying to speed up a program by using std::async. Let's say I have a function T* f (const T& t1, const ... -4.6.3 on Linux if 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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586 views

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c++ - ADL with typedefs from another namespace

I have something like this: #include <iostream> namespace N { typedef std::pair<int, double> MyPair; std::ostream& ... .g. in this case. 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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530 views

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c++ - Time complexity of removing items in vectors and deque

I have read that time complexity of adding items to end of a std::vector is amortized constant and inserting items ... any index will be zero? See Question&Answers more detail:os...

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

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275 views

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c++ - Why can't I put a "using" declaration inside a class declaration?

I understand the troubles you can get into when you put a using declaration inside a header file, so I don't ... ) if there's a workaround? 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 was Wrong with void main()?

Why has setting the entry point's return type to void in C++ always been discouraged, and was later removed by ... )? What was wrong with 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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288 views

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c++ - Move constructors and inheritance

I am trying to understand the way move constructors and assignment ops work in C++11 but I'm having problems with ... . What am I doing 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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414 views

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c++ - How to add one day to a time obtained from time()

I have a time represented as the number of seconds elapsed since midnight, January 1, 1970, UTC (the results of an ... your help and advice.... See Question&Answers more detail:os...

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

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513 views

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c++ - file name matching with wildcard

I need to implement something like my own file system. One operation would be the FindFirstFile. I need to ... this file name matching? 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++ - gdb error not in executable format: File format not recognized

I am trying to debug a simple "hello world" C++ program on Ubuntu 16.04 but gdb is not able to ... another Ubuntu 16.04 virtual machine. 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++ - map::emplace() with a custom value type

I'm having trouble using map::emplace(). Can anyone help me figure out the right syntax to use? I ... with custom types instead of primitives. See Question&Answers more detail:os...

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

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381 views

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c++ - Can we alias a class name the way we do in namespaces?

Can we alias a class name the way we do in namespaces? For example: namespace longname{ } namespace ln = ... class name aliasing, if allowed? 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++ - Return Optional value with ?: operator

I often need to use optional type for functions: std::optional<int32_t> get(const std::string& field) { auto it = map. ... ? it->second : {}; ^ See Question&Answers more detail:os...

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

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233 views

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c++ - Define variable b of the same type as variable a

Is it possible to declare a variable var_b of the same type as another variable, var_a? For example: template <class T> ... F_2 bar(T_2 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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410 views

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c++ - What is the purpose of std::byte?

Now that c++17 has std::byte, I was looking for a way to convert code that reads files to char into ... used for reading files, not characters. See Question&Answers more detail:os...

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

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