Recent questions tagged C++

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c++ - Macro concatenation using compiler define

This should be simple, but I'm struggling to figure it out. I have PROJECT_NAME as a compiler (g++) ... before the concatenation takes place? 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++ - Set precision with fstream to output file - format double

I cannot find an answer for how I might use an already opened fstream to output formatted doubles to a text file ... and such(2-decimal places) 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 function-definition is not allowed here before '{'

i am getting a REALLY annoying error. i literally looked everywhere for it! i even went back and changed all ... broke. fixing it now. 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++ - Floating Point Math Execution Time

What accounts for the added execution time of the first data set? The assembly instructions are the same. With DN_FLUSH ... = %dms ", duration); 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++ - Move constructor for derived class

I have 2 classes: template<typename T> class base{ T t; public: base(base &&b): t(std::move(b.t)){} }; ... Is it possible to do such a thing? 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++ - Global qualification in a class declarations class-head

We found something similar to the following (don't ask ...): namespace N { struct A { struct B; }; } ... ... or am i overlooking something? 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 my uninitialised_allocator safe?

Following from this question, I want to use an unitialised_allocator with, say, std::vector to avoid default initialisation ... safe to do so. 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++ - QMediaPlayer resource error

I'm using Qt Creator 2.7.2 (Qt 5.1) on Windows 8 Pro x64. I'm having trouble with QMediaPlayer. There ... code 80040266 Any idea what's 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++ - pragma STDC FENV_ACCESS ON is not supported

I tried to slightly modify the example from the article: #include <iostream> #include <cfenv> #pragma STDC FENV_ACCESS ... touches upon 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++ - Parameter with non-deduced type after parameter pack

There is different behaviour in clang++ and g++ for the next program: #include <type_traits> #include <utility> ... compiler to accept the code? See Question&Answers more detail:os...

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

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438 views

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c++ - normalizing a list of doubles to range -1 to 1 or 0 - 255

I have a list of doubles in the range of anywhere between -1.396655 to 1.74707 could even be higher or lower, ... 255 * (value - min)/range 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++ - linux3/gcc46: "-fnon-call-exceptions", which signals are trapping instructions?

(Environment: gcc/g++ 4.6.1 in -std=gnu++0x mode on Linux 3.0 / x86_64...) #include <stdlib. ... 30 #define SIGSYS 31 #define SIGUNUSED 31 See Question&Answers more detail:os...

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

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371 views

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c++ - Override initial value of a member variable of base class

I am very confused with the inheritance right now. I planned to simply override the initial value of a variable. In ... delete b; return 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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554 views

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c++ - toupper returns integer rather than char

for the following function void display() { for (int i = 0; i < 8; i++) { for (int j = 0; j < ... is it some sort of scope issue with toupper? See Question&Answers more detail:os...

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

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358 views

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c++ - this pointer to base class constructor?

I want to implement a derived class that should also implement an interface, that have a function that the base ... would like to avoid 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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430 views

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c++ - How to turn off beeping when pressing ENTER on a single-line EDIT control under Windows CE?

I'm developing an application targeted to a POCKET PC 2003 (Windows CE 4.2) device using C++ and native ... about 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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341 views

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c++ - Is TR2 Going to be Released in C++17?

There is lots of sweet stuff in TR2. Is that going to be in C++17? I understand that TR1 was completed in 2005 ... about TR2, but I am hoping... See Question&Answers more detail:os...

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

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481 views

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c++ - Idiomatic way to write concept that says that type is a std::vector

I have the following code that implements following type traits: that type is std::vector that type is std::vector of ... cout << func (vi); } 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 move around 1000 items in a QGraphicsScene without blocking the UI

I have around 1000 graphics item in my QGraphicsScene. I want to move all of these 1000 items to new ... looking forward to hearing 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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482 views

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c++ - Quicksort infinite loop if there are repeating values

I have a quicksort program that works great until I try to sort an array that has a repeating number. The program gets ... 1], size-lower-1); } See Question&Answers more detail:os...

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

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371 views

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c++ - Token pasting and __LINE__

I'm writing a simple macro to show TRACE information. This is what I'm using , #ifdef __DEBUG__ #define TRACE ... #endif --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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344 views

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c++ - SFINAE: checking the existence of a function breaks when the overload is moved to other namespaces

I want to check for the existence of a function in a specific namespace using SFINAE. I have found ... in a single feature_test namespace. See Question&Answers more detail:os...

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

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285 views

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c++ - How can I update code::blocks to use TDM-GCC?

I need to use unique_ptr in my C++ assignment. I downloaded a new compiler, TDM-GCC-4.7.1, and installed it. ... OS I use is Window 7. 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++ - C++11 constexpr function compiler error with ternary conditional operator (?:)

What is wrong with this piece of code? #include <iostream> template<unsigned int N, unsigned int P=0> ... :10:37: instantiated from 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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520 views

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c++ - Could not find the following Boost libraries: boost_system

I want to build this repository: https://github.com/reo7sp/tgbot-cpp. It is an API for managing Telegram bots ... success. Please, help me. See Question&Answers more detail:os...

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

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370 views

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c++ - Using LibTiff in Visual Studio 2010

I'm trying to use LibTiff in a C++ Program in Visual Studio 2010. I downloaded tiff-3.9.2.zip from ftp:// ... need help... Thank you so 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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531 views

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c++ - Check for arguments type in a variadic template declaration

I got a plain variadic template declaration, just like the classic one: template <typename... Arguments> class ... recognize where it was :P See Question&Answers more detail:os...

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

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489 views

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c++ - Compiler warning: lambda return type cannot be deduced

Consider this example: #include <algorithm> #include <iostream> int main() { std::string str = " ... say anything about 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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