General C++ Programming - March 2023

Potentially-evaluated expressions
An expression is potentially evaluated unless it is the operand of the sizeof, noexcept, typeid, decltype etc..
[19 replies] Last: [quote=malibor] static_assert is a good trick to see if it's evaluate... (by Peter87)
parsing durations using %q or %Q??
cannot parse durations using %q or %Q...e.g. std::chrono::duration<long long, std::milli> dur{ 1200 }; std::istringstream sm{ "1000ms" }; auto str =...
[5 replies] Last: Maybe something like: #include <chrono> #include <iostream> #includ... (by seeplus)
parsing a formatted string
using the format library in C++20, and having done this: int val = 25; string str = std::format( "{0:2}", val); How can we get the val from str, somethin...
[6 replies] Last: To just obtain a number from std::string, there are the stoxxx functio... (by seeplus)
I don't understand ISO week
Please explain why Sunday jan 1, 2023 prints as 52 using %V -- why is that different to week 1? week 1 starts with Jan 1 for every year... Doesn't make...
[1 reply] : [quote=JUANDENT]week 1 starts with Jan 1 for every year... Nope. Eve... (by Peter87)
now() returns same as current_zone()->to_local(now())
Hi, system_clock::now() returns the same value as chr::current_zone()->to_local(now()); I expected now() to return UTC value and to->local(now()) to return CS...
[1 reply] : A quick search reveals: (by TheIdeasMan)
Should destructors be noexcept?
I'm working on a library which whose classes are almost all hierarchical, problem is that if upmost class destructor is declared noexcept then all destructors i...
[13 replies] Last: There is nothing in the C++ standard that demands that this should ge... (by malibor)
Need Help to find the error
I have below code, for functor. But this is giving compilation error in VS17. #include <iostream> #include <functional> template <typename T> struct less...
[3 replies] Last: Now I understand, the problem. Yes thanks to both of you for the clari... (by shekharsahoo)
where can I find trim() in std C++?
I expected std::string to have a member function trim() but it does not. How to accomplish this??
[4 replies] Last: Using ranges, then possibly something like this which will trim white-... (by seeplus)
is this object dangling?
hi, I have this code assert(ltrim_copy(str) == "ยข4,500.55"); // line 1 ltrim_copy returns a temporary object... is it ok to compare it with...
[1 reply] : it's OK and it is destroyed when assert returns. (by malibor)
Neuronal Network not working properly..
Dear Community, I'm wondering what I'm doing wrong when it comes to building neural networks and I can't come up with a solution on my own. I want to build a...
[4 replies] Last: You implementation is missing a "Neuron" class, "Layer" class, "Synaps... (by malibor)
how can a function name be an lvalue?
take this function: int abs(int a) { return a < 0 ? -a : a; } abs is supposed to be an lvalue but it cannot be assigned!! int xy(int);...
[8 replies] Last: [quote=seeplus]In my mind (and the language lawyers will probably squa... (by Peter87)
by Cplusc
blockMesh generator
Following my question regarding hexahedral mesh generation in a domain using the STL file representing the surface triangulation here
[10 replies] Last: > Actually this is not a big code at all Big enough for you to dump on... (by salem c)
Age calculation
With C++20/23 std::chrono and a birthdate as either type sys_days or year_month_day, is there any 'easy' way to obtain their age as years, months and days. It's...
[1 reply] : We've come up with this: struct Age { unsigned years {}; unsigned... (by seeplus)
by Cplusc
Building project from github
I'm trying to build this project This project has several dependencies. I have several of them installed in my system ...
[4 replies] Last: vcpkg is used with Visual Studio. step 1: install all deps with corre... (by malibor)
Force implicit conversion of a string literal in templated class?
The code below doesn't compile because string literal instead of std::string is given to constructor. #include <string> #include <type_traits> template<typ...
[3 replies] Last: C++17! (by mbozzi)
by Cplusc
generate mesh inside .STL file
I have some STL files (usually aneurysm) and I'm using Lattice Boltzmann Method for my simulation and I need to construct the mesh. As far as LBM uses cubic mes...
[18 replies] Last: I would strongly appreciate any idea on my way of generating mesh insi... (by Cplusc)
year_month_day vs sys_days
When dealing with dates - year, month, day (not times) - either year_month_day or sys_days can be used. Is there guidance as when one or the other should be use...
[9 replies] Last: [quote=seeplus]When do you get 8 for sys_days? libstdc++ (64-bit) htt... (by Peter87)
Chrono date literals
Since C++20 there has been the d and y literals defined in <chrono> - but no m. This seems to be able to be added by (for VS - based upon the code for d and ...
[4 replies] Last: I get forward thinking & future planning, but c++ has no business stan... (by jonnin)
How can I find the maximium number of decimal digits representable in a double?
What is the maximum precision of double? numeric_limits<double>::????? default precision is 6 digits after the period
[3 replies] Last: (by Peter87)
output will show only the end.
Hello everybody. I really thank you for helping me to go back to programming in C++. You know I am now 73 years old. They told me I have to stay busy to sta...
[6 replies] Last: What exactly do you want to know? Let's say your terminal/cmd has 100 ... (by Ganado)
March 2023 Pages: 12
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