Questions tagged [c++]
C++ is a general-purpose programming language. Use this tag for questions about/utilizing C++. Do not also tag questions with [c] unless you have a good reason. C and C++ are different languages. Use a versioned tag such as [c++11], [c++20] etc. for questions specific to a standard revision.
117
questions
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views
How should I modify my code so that mouse-drawn lines remain on the canvas of the window during window scrolling
I am using win32 api to make a paint program, when I try to solve that using mouse to draw lines,remain the lines in the canvas, it can't work well.
This is the Win Process Function:
LRESULT ...
- 3
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66
views
Lossy conversion between long double and double
I was cought by suprise that the following code returns false for gcc 13 and clang 18. Why does this happen? Isn't the number 8.1 representable in both formats?
#include <iostream>
#include <...
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2
votes
1
answer
72
views
Order of c++ template arguments affecting compilation
I just encountered a new compilation error in my code after a visual studio update. I have stripped my code down to what I think is a minimal example. I have two templated functions both called pow - ...
- 1,757
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2
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27
views
Strange results while trying to make matris symmetric in Eigen
In my project i work with covariance matrices and during many repetitive operation i have noticed that they gradually loose their symmetry. I put it down to numerical problems and when loss of ...
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2
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74
views
Why did std::sort use this simple strict weak ordering compare still crash? [duplicate]
Here is my code:
#include<vector>
#include<algorithm>
#include<iostream>
using namespace std;
void test()
{
vector<vector<int>> info = {{0,0,999}, {0,1,1000}, {0,2,...
- 71
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33
views
Runtime error: addition of unsigned offset in leetcode
I was solving a question on Leetcode(322. Coin Change) and I wrote my solution which is working on VScode. the code is:
int coinChange(vector<int>& coins, int amount) {
int n = coins.size(...
2
votes
0
answers
42
views
Vulkan - VK_ERROR_INCOMPATIBLE_DRIVER error in Apple M2
With this code:
#include <vulkan/vulkan.h>
#include <iostream>
#include <stdexcept>
#include <cstdlib>
#include <vector>
class HelloTriangleApplication {
public:
...
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0
answers
11
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MPI failed to run on more than one host with OFI poll failed error
I am using MPICH 4.2.2 on Ubuntu 24.04 testing with the small program cpi that calculates the value of pi using MPI. I can start on host1 to run cpi on either host1 or host2 alone and I can start on ...
- 782
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27
views
Extension of lifetime for inner fields when the type's lifetime is extended?
I am pondering about a piece of tooling code that we were using for a while here now, but which I suspect is actual undefined behaviour (at least, I got a couple of debugging sessions where it looks ...
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30
views
Issues with QGraphicsPixmapItem handling Mouse Events in QGraphicsScene
I created an object:
class Button : public QObject, public QGraphicsPixmapItem
{
Q_OBJECT
next I implemented a few functions:
Button::Button()
: m_pressed(false)
{
m_buttonPixmap = ...
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0
answers
17
views
OpenMC Statepoints and Tally
OpenMC is a C++ open-source software for neutron transport calculations.
openmc is an homonymous Python library that binds Python to OpenMC.
I have no training to OpenMC and tried to figured out from ...
- 147
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1
answer
14
views
QTableView not showing QPixmap
I'm trying to show a list of media files with Qt. For that I'm using a QTableView with a column for the preview and a column for the file name. With the following code, the file name is shown but the ...
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6
votes
3
answers
278
views
Is it safe to move object inside its destructor
I'm 99% sure the answer to my question is 'Yes'. I just want to double check my assumption is right and I want to be sure that there is nothing in the upcoming C++ standards that could change the ...
- 994
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23
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How to custom cpp var value in gdb and clion > watches
see my img, I find zoned_time can show custom str "America/New_York" 1721904914882986761ns [2024-07-25 10:55:14]
how to custom this value in my own class
I try following code but it only ...
- 4,025
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0
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32
views
Composing boost program options to get a multiline string
I am resuming C++ programming after 20 years by taking up C++ 20 standard and I try to read a multi-line configuration from an .ini file with boost's program_options. As .ini files do not support \r\n ...
- 448