Most active questions
16,656 questions from the last 30 days
24
votes
5
answers
2k
views
With Clang or similar compilers, is it possible to turn only some warnings into errors?
Compiler warnings generally provide useful hints for common programming errors. It is often recommended to turn compiler warnings into errors (e.g. here). In my experience, this is useful to prevent ...
22
votes
6
answers
4k
views
Why use a mutex and not a semaphore?
Looking in cppreference, it seems to imply a std::binary_semaphore may be more efficient than a std::mutex.
Is there any reason not to use a std::binary_semaphore initialized to 1 instead of a std::...
- 21.9k
25
votes
3
answers
1k
views
Only copiable type not accepted in msvc std::vector implementation
In the following code:
struct copy_only
{
copy_only() = default;
copy_only(const copy_only&) = default;
copy_only& operator=(const copy_only&) = default;
...
- 34.3k
14
votes
5
answers
723
views
How can I negate a logical value in a base R pipeline?
Running
TRUE |> `!`()
Results in:
Error in !NULL :
function '!' not supported in RHS call of a pipe (<input>:1:9)
When using magrittr, there is a not() alias, but this does not work for ...
- 472
9
votes
7
answers
1k
views
Reformat numbers, inserting separators at fixed positions
There are many lines in a file, like the following:
000100667 ===> 000102833
005843000 ===> 005844000
011248375 ===> 011251958
I would like to insert specific separators into the numbers ...
- 135
13
votes
5
answers
599
views
How to return the results only when matching is true in R gsub()
I'm working with a character vector in R (test) where I need to extract specific parts of strings that match a pattern while discarding the original strings that don't match.
My current solution is ...
- 133
14
votes
3
answers
2k
views
How to create a uint64 whose lower and upper bits reference uint32s?
auto lo = 0u;
auto hi = 1u;
auto combined = (((std::uint64_t)hi) << 32) | lo;
But if I do combined++ then lo and hi are not changed, because combined is a copy.
How do I make the lower bits of ...
- 153
14
votes
3
answers
2k
views
Why is it ok to cast to an undeclared struct pointer in C?
Why does this code compile? struct test is not even forward declared.
int main(){
*(int*)((struct test*) 0x1234) = 0x0;
return 0;
}
- 3,038
26
votes
1
answer
906
views
How to find the Nth weekday of the month using chrono?
There are lots of SO Q/A's solving this problem in other languages, but not
so much in C++.
How do I find the Nth weekday of the month using <chrono>? For
example what is the day of the month ...
- 222k
22
votes
1
answer
1k
views
Find next weekday using chrono
Given a year, month and day, how do I find the next weekday on or after that
date? For example, If I have 2025-04-28, how can I find the Friday
following 2025-04-28, which is 2025-05-02?
What about ...
- 222k
5
votes
7
answers
2k
views
Dependency 'androidx.browser:browser:1.9.0-alpha02' requires libraries and applications that [closed]
A failure occurred while executing
com.android.build.gradle.internal.tasks.CheckAarMetadataWorkAction
Dependency 'androidx.browser:browser:1.9.0-alpha02' requires libraries and applications that ...
- 237
12
votes
2
answers
470
views
How can I disable concept evaluation result caching?
It appears that all compilers perform caching of concepts' evaluations. So if some concept was evaluated as false once, it will not be reevaluated again for the same argument:
template <typename T&...
- 22.6k
18
votes
3
answers
1k
views
Android DataStore: unresolved Reference edit, stringPreferencesKey
I'm writing an Android app that is using DataStore. I'm failing to compile even a stripped-down version of it - I always get a compilation error for the import statements saying unresolved Reference ...
- 183
10
votes
6
answers
549
views
Filter data.frame by list
I want to be able to filter a given data.frame by a dynamic list.
Lets say I have a list of filters like this
filter_list = list(filter_1 = list(vs = c(0), carb = c(1,4)),
filter_2 =...
- 2,673
7
votes
7
answers
231
views
awk to extract a block of text
I am trying to figure out an awk command/script to extract a block of text from a large file. The file subsection I am interested in is this:
Board Info: #512
Manufacturer: "Dell Inc."
...
- 371