1,467 questions
-3
votes
0
answers
42
views
Why would you advise someone "x should be implemented as an enum and not a sum type"? [closed]
I'm reading the design documentation for IPLD, and in a discussion about Kinds, it advises
Kind must be an enum, and not a sum type. Attempting to implement kind as a sum type conflates it with Node.
...
- 1,443
33
votes
2
answers
2k
views
What's the point of deleted virtual functions?
Apparently you can =delete virtual functions:
struct A
{
virtual void foo() = delete;
};
struct B : A
{
void foo() override = delete;
};
Interestingly, both functions have to be =deleted, or ...
- 98.7k
5
votes
1
answer
191
views
Is there really not cross product in std::linalg and if yes why?
I know for sure how to calculate a cross product myself, but usually I tree to use the standard library where possible.
I am aware that std::linalg is still in development so this might already be the ...
- 778
0
votes
2
answers
171
views
Why ISO C++ forbid taking the address of a bound member function to form a pointer to member function?
Here is the error in GCC (which i have already fixed):
ISO C++ forbid taking the address of a bound member function to form a pointer to member function
This is the error line of my code:
threads[i] ...
- 11
0
votes
2
answers
173
views
Why is the virtual keyword applied to methods instead of classes
When the virtual keyword is applied to a method the whole class becomes abstract.
Shouldn't the virtual or abstract keyword be applied to the class? It is a more intuitive design because it reflects ...
- 51
13
votes
1
answer
429
views
Why doesn't the C++ standard implicitly define a lambda capturing nothing as `static` by default?
C++23 allows to define a lambda as static. i.e. If a lambda captures nothing, then it can be defined as static:
// with superfluous argument `this`, less efficient.
auto fn1 = [](int a, int b) { ...
- 42.6k
4
votes
1
answer
162
views
Why doesn't std::array's operator[] retain the value category of the array?
I'd have expected that if an std::array is an rvalue, then calling operator[] returns an rvalue as well. But it doesn't seem to be the case (cppreference), there are no value-category overloads.
For ...
- 30.1k
0
votes
1
answer
80
views
A hash function that maintains mathematical equality (especially for sets)
I'm working on a little math-based programming language (written in Rust) that uses sets instead of types. In it, a variable or value belongs to a set of values (eg. x : {1, 2, 3} or msg : Str). The ...
- 5
1
vote
1
answer
78
views
How to implement ordered fan-in (proper message passing for my language)?
I'm the creator of https://github.com/nevalang/neva
It's a dataflow programming where you have nodes that do message passing through ports. I use go channels to implement that. However, I faced an ...
- 81
2
votes
2
answers
119
views
Why does `std::integral_constant` have a `::type` that refers to itself?
I'm reading the documentation on std::integral_constant, and apparently it includes using type that refers to itself.
template <typename T, T Value>
struct integral_constant
{
using type = ...
- 98.7k
4
votes
1
answer
146
views
Why does the standard require only input iterators for std::distance, rather than forward iterators?
I was perplexed to see that the template parameter requirement for std::distance is a LegacyInputIterator rather than a LegacyForwardIterator.
Since input-only iterators don't have the multi-pass ...
- 2,214
3
votes
1
answer
212
views
Why there is no std::numbers::sqrtpi_v?
I have a std::normal_distribution<RealType> normal_distribution and want to use its normalization constant in a constexpr. Unfortunately, I cannot use normal_distribution.stddev() * std::sqrt(2 *...
- 18.3k
3
votes
0
answers
46
views
Why is the overload for both the == and <=> operator required to overload all comparison operators? [duplicate]
I was going through this guide on operator overloading in C++.
If I try to implement all the comparison operators using the <=> operator:
friend auto operator<=>(const Some_class& lhs, ...
- 389
1
vote
3
answers
190
views
Why don't STL containers have methods for general funcitons?
I understand that there are general functions on iterators that accomplish everything you would want to do, such as std::find, std::count etc. but why don't the standard containers such as std::vector ...
- 86
6
votes
1
answer
583
views
Why `std::string_view` is not modifiable?
I start experiment with std::string_view.
It has a very ugly feature. You cannot say:
std::string_view<const char> and std::string_view<char> like the awesome std::span.
So, you cannot ...
- 2,187