Recent questions tagged C++

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c++ - How do I portably add a large number of seconds to a time_t object?

Well I think the title sums it up. Suppose I have an object of type double which I obtained from running std:: ... Surely there's a better way!? 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++ - Share an object between QML files

I'm new to coding in QML and I'm trying to write my first Sailfish OS app. For the backend I have ... same object in the separate QML 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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286 views

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c++ - Difference between clock() and MPI_Wtime()

Quick Question . for MPI implementation of my code ,i am getting a huge difference in both. I know MPI_Wtime ... wants to add some assertion ? 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 any way of detecting arbitrary template classes that mix types and non-types?

Is there any way of detecting whether a class is a normal type or is an instantiation of a template type ( ... templates just by an identifier? 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 set console font to Raster Font, programmatically?

How do I make sure that the command prompt's current font is the default Raster Font, at runtime? I'm using ... font does not change, though. See Question&Answers more detail:os...

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

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313 views

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c++ - Using (or not using) parentheses when initializing an array

In the c++ code that I am reading through there are some arrays initialised like int *foo = new int[length] ... look at the answers for details 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 am I getting a different result from std::fmod and std::remainder

In the below example app I calculate the floating point remainder from dividing 953 by 0.1, using std::fmod What I was ... , fmod: 0.1, rem: 0 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 make 'send' non-blocking in winsock

I am making a program which sends UDP packets to a server at a fixed interval, something like this: while ( ... into a non-blocking operation? 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++ - "Invalid covariant return type" errors in nested classes with methods returning template-based objects

The following C++ code gives me these errors when compiled: covariant.cpp:32:22: error: invalid covariant return type for ... <B> test() {} }; 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 find the shortest path that covers all nodes in a directed cyclic graph?

I need an example of the shortest path of a directed cyclic graph from one node (it should reach to all nodes of ... in C++, or the algorithm. 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++ - Sign extension with bitwise shift operation

following this Q&A I tried to exam the answer so I wrote: #include <stdio.h> int main () { int t;int ... 0xFFFFFFFF if t declared as integer ? 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++ - Visual Studio error: LNK1104: cannot open file 'kernel32.lib' - only in WP8 projects / Win32 builds

I ran into this problem recently (few days ago everything was working fine): Visual Studio 2012 started to refuse ... no problem. Is it normal? See Question&Answers more detail:os...

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

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238 views

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c++ - MSVCP110D.dll and Visual Studio 2013

I am trying to run a program I compiled in Visual Studio 2013. However, I get the error The program can't ... Release mode using an x64 build. See Question&Answers more detail:os...

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

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251 views

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c++ - Performance of Dijkstra's algorithm implementation

Below is an implementation of Dijkstra's algorithm I wrote from the pseudocode in the Wikipedia article. For a graph ... to prev for output } } See Question&Answers more detail:os...

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

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460 views

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c++ - Why do non-const, non-int/enum static data members have to be initialized outside the definition?

I understand that only data members which are static, const and int/enum (pre c++11) can be initialized ... scope relevant to their class? See Question&Answers more detail:os...

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

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262 views

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c++ - Trivial Destructibility and Necessity of Calling Destructor

Suppose there exists a type T such that std::is_trivially_destructable<T>::value == true, and suppose further that ... ? 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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196 views

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c++ - Close all File Handles when Calling posix_spawn

I'd like to spawn a collection of processes using posix_spawn(...) (or something very similar). This ... this problem would be preferable. See Question&Answers more detail:os...

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

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259 views

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c++ - What is the difference between infinite while loops and for loops?

I see the different conventions used in many books I had read, where you would create infinite loops with either ... ? which one is better? See Question&Answers more detail:os...

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

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378 views

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c++ - Proper casting for fstream read and write member functions

Although there was a lot of lines written on the topic of reinterpret_cast, and how bad it is, I'm ... as standard-conforming as possible. See Question&Answers more detail:os...

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

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338 views

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c++ - Can multiple threads write the same value to the same variable at the same time safely?

Can multiple threads write the same value to the same variable at the same time safely? For a specific ... necessary for this specific 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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192 views

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c++ - Can the main function be a template? (safe command line argument parsing)

Can the main function be declared like so : template<typename T1, typename T2> int main(T1 argc, T2 *argv[]) ... I invented the wheel 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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337 views

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c++ - SEGFAULT in -O3 mode?

I summarized my problem to the following short program. It causes SEGFAULT in -O3 mode only (-O2 works fine). ... , 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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264 views

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c++ - .dll Plugin that uses functions defined in the main executable

I have a Main executable that loads .dll/.so Plugins, which works just fine in Linux but on windows(Visual ... without a million #ifdef's? See Question&Answers more detail:os...

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

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355 views

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c++ - Move semantics in Eigen

I have couple of question about Eigen: Does anyone know if there is any plan to support move semantics in Eigen ... bet is to use swap()? See Question&Answers more detail:os...

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

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225 views

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c++ - Correct way of checking if threads are done?

I'm using multithreading in my application with _beginthread and right now to wait until all threads are done I ... way of doing this? 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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350 views

1 answer

c++ - How does behave linux buffer cache when an application is crashing down?

Let's say I am using c++ files stream asynchronously. I mean never using std::flush nor std::endl. My ... disk, or discarded (and lost)? See Question&Answers more detail:os...

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

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253 views

1 answer

c++ - Fast code for searching bit-array for contiguous set/clear bits?

Is there some reasonably fast code out there which can help me quickly search a large bitmap (a few megabytes) ... (for defragmentation, etc.). See Question&Answers more detail:os...

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

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565 views

1 answer

c++ - OpenCV: Using Hough Circle Transformation to detect iris

I am newbie to openCV, but I want to create iris recognition program. Although the system with webcam can detect ... ( "circles", capturedImg ); See Question&Answers more detail:os...

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

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