Recent questions tagged C++

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c++ - Why does outputting a class with a conversion operator not work for std::string?

This works, printing 1: #include <iostream> struct Int { int i; operator int() const noexcept {return i;} }; ... with int, but not std::string? 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 all classes have a Vtable created for them by the compiler?

There are many resources online about VTables. They commonly have the same statement regarding them: "Whenever a ... 't have virtual 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++ - How does one hide a win32 app window?

I want to run the app in silent mode by passing in a parameter, otherwise I will show the window. 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++ - Virtual Functions: Iterating over a vector<Base Class> that is populated with subclass objects

Short Description: I am iterating over a vector calling a virtual function on every object in the vector in ... would be greatly 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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c++ - Is there a way to deduce the signature of a lambda as an mpl sequence?

Is there a way to deduce the signature, result- and parameter-types, of a c++0x lambda as a Boost.MPL sequence ... :mpl::vector<void,float,int>. 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 the value category of string literals?

I'm pretty sure the value category of integer, character, boolean and floating point literals is prvalue. User ... How did you determine 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++ - Undefined behaviour of operators in XOR swap algorithm?

void swap(int* a, int* b) { if (a != b) *a ^= *b ^= *a ^= *b; } As the above *a ^= *b ^= * ... matter whether I write it in C99/C11/C++98/C++11? 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 get element from std::tuple by type

I have a set of classes A, B, C and I want to have access instances of them from generic code by type, ... of newObject for each type.:-) 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 have an out-of-process COM server where a separate O/S process is used for each object instance?

I have a legacy C++ "solution engine" that I have already wrapped as an in-process COM object for use by ... object requested. Am I in luck? 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 use Boost::Spirit::Lex to lex a file without reading the whole file into memory first?

I'm looking at writing a lexer using boost::spirit::lex, but all the examples I can find seem to assume ... from lex tokens somehow? 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++ - What is MAKEWORD used for?

I have come across this macro MAKEWORD(2,2) in a piece of instructional code. I read in MSDN that it " ... procedure such as using MAKEWORD()? 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 bring global function into the overload resolution with member function?

Here is the corresponding question, what I want to know is, Is it possible to bring global function into the overload ... member foo "; } }; 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++ - libpng error: PNG unsigned integer out of range

When trying to read a PNG from memory I came across this funky error: libpng error:: PNG unsigned integer ... .com/s/m5enp9jljglhs5c/test.png 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 a derived class not access a protected member of its base class through a pointer to base?

This is the code: class TestA { protected: int test=12; public: TestA() { cout << "test a: " ... Not outside using pointer/direct declarations? 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 QThread when application is being closed without proper wait() call?

In the example below (inside Qt GUI application) a new thread is started (with an event loop in which I want ... the application to close. 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++ - error C2248: 'std::basic_ios<_Elem,_Traits>::basic_ios' : cannot access private member declared in class 'std::basic_ios<_Elem,_Traits>'

I am unable to understand this error.This error is not in the class that i am debugging . (Is it ?) ... int hisRoomNumber , string hisName ); See Question&Answers more detail:os...

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

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488 views

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c++ - How does Stroustrup's Can_Copy template work?

Stroustrup provides a Can_copy template. How does it work? template<class T1, class T2> struct Can_copy { static ... uses as an optimisation? 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++ - Setting the precision of a double without using stream (ios_base::precision)

Is there a way to do this without using the stream? For example, something like this: double a = 6. ... am curious. 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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367 views

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c++ - const CFoo &bar() const

I have a property of a class, for example, const CFoo &bar() const, what does it mean? See Question&Answers more detail:os...

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

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562 views

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c++ - Commutative operator overloading + of 2 different objects

I have 2 classes which represent a matrix: 1. RegularMatrix - O(n^2) representation 2. SparseMatrix - a matrix ... decides by itself? 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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288 views

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c++ - Why can't my object access protected members of another object defined in common base class?

The following code produces a compiler error: 'BaseTest::_protMember' : cannot access protected member declared in ... of another instance? See Question&Answers more detail:os...

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

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281 views

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c++ - How can I pass a dynamic multidimensional array to a function?

How can I pass a multidimensional array to a function in C/C++ ? The dimensions of array are not known at compile time 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 the reason of QVector's requirement for default constructor?

I can see that that classes are treated as complex objects which are required for calling default constructor: void QVector ... ~Wrapper() {} }; See Question&Answers more detail:os...

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

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384 views

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c++ - Overload of operator<< not found when called from std::ostream_iterator?

This program // main.cpp #include <iostream> #include <utility> #include <algorithm> #include <iterator> #include <map> ... , but why is 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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395 views

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c++ - Optimizing a Loop vs Code Duplication

My dilemma concerns how to best handle long heavy loops which can accept parameters. Consider the following method: ... outside of the loop. See Question&Answers more detail:os...

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

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320 views

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c++ - Sequence point from function call?

This is yet another sequence-point question, but a rather simple one: #include <stdio.h> void f(int p, int) { ... (&p) act as a sequence point? See Question&Answers more detail:os...

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

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274 views

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c++ - What does it mean when the first "for" parameter is blank?

I have been looking through some code and I have seen several examples where the first element of a for cycle ... What does this mean? 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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472 views

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c++ - No console output on cout

Good morning, I have a problem with Eclipse IDE for C/C++ Developers. I'm writting a smal tool for ... something obvious? 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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