Recent questions tagged C++

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c++ - Is there a shorter way to forward declare a class in a namespace?

I can forward declare a function in a namespace by doing this: void myNamespace::doThing(); which is ... of: class myNamespace::myClass; 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++ - Would you use num%2 or num&1 to check if a number is even?

Well, there are at least two low-level ways of determining whether a given number is even or not: 1. if ... - As some comments righfuly state. 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++ - auto from const std::vector<>&; object or reference?

suppose we have an object with the following interface: struct Node_t { ... const std::vector< something >& ... or a reference to 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++ - _ITERATOR_DEBUG_LEVEL error in visual studio

I am trying to compile JRTPLIB in Visual Studio 2010 on windows 7. It's been a true nightmare... but I'm ... with the defaults I guess. Cheers 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 use of a constexpr on a non-const member function?

The accepted answer in literal class compile error with constexpr constructor and function (differ vc, g++) ... non-const member function? 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++ - pass method with template arguments to a macro

I am unable to use Google Test's ASSERT_THROW() macro in combination with multiple template arguments. Consider ... this problem? 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++ - Templates spread across multiple files

C++ seems to be rather grouchy when declaring templates across multiple files. More specifically, when working ... across multiple files? 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++ - Source line length limit

What's the maximum length of a source line all compilers are required to accept? Did it change in C++11? If ... code because of too long lines. 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 qmake put all object (.o) files to one directory?

Let's say I have a Qt application where I have two classes with the same name in two different namespaces: ... - except object files placement. 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++ - emplace_back() does not behave as expected

I wrote a simple program to play around with in-place creation of objects inside standard library containers. This ... ? 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++ - Why does the rvalue overload of `operator<<` for `basic_ostream` return an lvalue reference?

§27.7.3.9 defines the following overload for operator<<: template <class charT, class traits, class T> ... overload returns an lvalue reference? 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++ - NULL check before deleting an object with an overloaded delete

This came up as one of the code review comments. Is it a good idea to check for NULL before calling delete for ... hold good. What do you think? 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 compilers automatically use move semantics when a movable object is used for the last time?

I've been studying rvalue references lately and came to a conclusion that it's quite advantageous to use ... apply Return Value Optimization? 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++ - Creating fstream object from a FILE* pointer

The well known way of creating an fstream object is: ifstream fobj("myfile.txt"); ie. using a filename. ... * pointer involved but no filename. 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 a constructor return a NULL value?

I know constructors don't "return" anything but for instance if I call CMyClass *object = new CMyClass() is ... do that? 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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c++ - Is there a Boost.Bimap alternative in c++11?

Is there a usable alternative to Boost's bimap in C++0x? I would like to avoid Boost, but fully embrace C++11 ... are equally fine in my 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++ - Why does std::set seem to force the use of a const_iterator?

Consider the simple program below, which attempts to iterate through the values of a set using NON-const references to ... use that in 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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c++ - Ctor not allowed return type

Having code: struct B { int* a; B(int value):a(new int(value)) { } B():a(nullptr){} B(const B&); } B: ... Any idea why? P.S. I'm using VS 2010RC 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++ - Sort Anticlockwise the points of rectilinear polygon

I am given a rectilinear polygon whose coordinates are given. Please suggest to me a solution to sort ... Please provide a solution. 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++ - Two's complement binary form

In a TC++ compiler, the binary representation of 5 is (00000000000000101). I know that negative numbers are stored ... 5 -6 (1111111111111010)? 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++ - Convert FreeImage FIBITMAP format to OpenCV Mat

I've been searching on an answer but all I can find is the inverse of what I need (Mat to FIBITMAP). I have a ... I already have. How do I do? 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++ - Opengl object extrusion

I've got a 3d box drawn in opengl, can someone explain how to extrude objects in opengl? do i just translate ... the z axis for each box? 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++ - array initialisation

I'm quite certain that arrays of built in types are unitialized, whereas arrays of UDTs are default initialized. ... to confirm the above? 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++ - OpenCV (CvHaarClassifierCascade*) cvLoad doesn't load, unable to load xml file

I'm trying face detection using OpenCv 2.3. My trying to load "haarcascade_frontalface_alt_tree.xml" on my ... lib, "opencv_video230d.lib") 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++ - Collision detection between two general hexahedrons

I have 2 six faced solids. The only guarantee is that they each have 8 vertex3f's (verticies with x,y and ... find out if these are colliding? 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++ - IP camera and OPENCV

Good day! I am using Dev-C++ as my IDE and the library OpenCV. I need to fetch the video taken by my IP ... 7 64 bit. Thank you very much.. See Question&Answers more detail:os...

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

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351 views

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c++ - Partial specialization: use the primary template members

Consider enum My_Enum { x1, x2 }; template<class T, My_Enum X> class A { void f1(); void f2(); }; template<class ... A<T,x1>.g() 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++ - OpenCV convexity defects drawing

I have stored the defects using convexity defects in an 4 element vector integer array using vec4i. My convex ... format! 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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