I’m trying to use a concept that applies to both built-in and user-defined types. In my setting, it is inconvenient to forward-declare certain functions (because the functions depend indirectly on the concepts causing my problem). My problem is that concepts don’t recognize functions that were not previously declared if those functions have arguments of built-in ..
Category : argument-dependent-lookup
The program as follows compiles fine in C++20: #include <memory> struct A{ virtual ~A() = default; }; struct B: A {}; int main() { std::shared_ptr<A> p = std::make_shared<B>(); auto x = dynamic_pointer_cast<A>(p); } But in C++17 it produces an error: <source>: In function ‘int main()’: <source>:9:14: error: ‘dynamic_pointer_cast’ was not declared in this scope; did ..
I’ve declared an operator<< overload for time_point in the global namespace and also one for a::Foo in the a namespace. When I try to print a time_point in a function also defined in namespace a, I get ther error: Invalid operands to binary expression. Why is this, and what is the best solution? #include <iostream> ..
Consider // https://godbolt.org/z/z5M9b9jzx #include <memory> #include <cassert> struct B {}; struct D : B {}; int main() { std::shared_ptr<B> b = std::make_shared<D>(); auto d = static_pointer_cast<D>(b); assert(d); } I’d’ve expected the unqualified call to static_pointer_cast to resolve to std::static_pointer_cast, because b, being a std::shared_ptr, should bring namespace std in using ADL. Why doesn’t it? I ..
My use-case is as follows – within a non-std:: namespace, a class has a templated member function which takes in 2 (templated) iterators as parameters, and part of the function call involves calling distance() on those iterators. The problem is, some containers have their own overload for distance() for their iterators. So if I specify ..
I have created a stream output operator for std::vector in my namespace, and I was able to use that in my previous debug code: namespace my_company { template <typename T> std::ostream &operator<<(std::ostream &os, std::vector<T> const &vec) { os << "{"; for (int i = 0; i < vec.size(); ++i) { if (i != 0) { ..
I implement a function named make_heap() in namespace dsa. and I get error when I tried to invoke it and std::make_heap() to make comparison. GCC told me that: call of overloaded ‘make_heap(dsa::Vector::iterator&, dsa::Vector::iterator&, std::greater)’ is ambiguous The code is following, any suggestions? template<typename _Random_It> void make_heap(_Random_It first, _Random_It last) { // get true value_type from ..
I’m having issues with ADL not finding hidden friends. I’m working on a c++20 codebase that is made to run on the latest versions of msvc however I’m moving it back a bit and getting it to compile with gcc 10.2.0 on arch linux. There are a few isolated places that are complaining about these ..
In the following code, the standalone component in the namespace S has its own definitions of Big and Small types, together with a split function to split one Big into a collection of the Smalls. S also provides another function, work, which makes use of split, and is meant to be used by S itself ..
If I have a structure the overloads begin, end, etc. like the following: #include <array> template<typename T> struct Array10 { private: std::array<T, 10> m_array; public: constexpr auto begin() { return std::begin(m_array); // #1 } constexpr auto end() { return std::end(m_array); } // cbegin, cend, rbegin, rend, crbegin, crend }; int main() { Array10<int> arr; std::fill( ..
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