I want to make my own struct for a 3×3 Matrix. I want to allow construction via components/elements or by "rows". So either you provide a std::array<float, 9> or a std::array<std::array<float, 3>, 3> However when defining the struct like this with the following constructors: struct Matrix3x3 { Matrix3x3(std::array<float, 9> components) { } Matrix3x3(std::array<std::array<float, 3>, 3> ..
Category : aggregate-initialization
I want to make my own struct for a 3×3 Matrix. I want to allow construction via components/elements or by "rows". So either you provide a std::array<float, 9> or a std::array<std::array<float, 3>, 3> However when defining the struct like this with the following constructors: struct Matrix3x3 { Matrix3x3(std::array<float, 9> components) { } Matrix3x3(std::array<std::array<float, 3>, 3> ..
I have a problem compiling this simple aggregate named initialization with g++ struct A { int a; }; struct B { int b; }; struct C { A a; B b; }; void fun() { A a{0}; B b {12} ; // g++ is OK with this C c{ .a=a , .b=b }; // g++ ..
I always thought that aggregate initialization was to save coders from writing custom constructors. However, this seems to have "sneaked in" a "security by-pass" for private constructors. Say I have class A which I only want to be created by class B. struct A { friend class B; const int i, k; private: A () ..
See this example: https://godbolt.org/z/5PqYWP How come this array of pairs can’t be initialized in the same way as a vector of pairs? #include <vector> #include <array> int main() { std::vector<std::pair<int,int>> v{{1,2},{3,4},{5,6}}; // succeeds std::array <std::pair<int,int>, 3> a{{1,2},{3,4},{5,6}}; // fails to compile } Source: Windows Que..
I want to make it possible to pass brace-enclosed initializer list to my constructor of my class which represents a matrix of fixed dimension. This is the code what I have: #include <cstddef> #include <array> template <typename T, size_t N, size_t M> using array2d = std::array<std::array<T, N>, M>; template <typename T, size_t N, size_t M> ..
I was reading on template deduction then tried to create one. as follows:- #include <iostream> #include <array> using namespace std; template<int i,typename A,typename… B> struct deducted{ }; //Deduction guide template<typename A,typename… B> deducted(A a,B… b)->deducted<0,A,B…>; // int main(){ deducted a={"","",""}; deducted b={0,0,0}; array c={0,0,0}; } what supprises me is the test fails with error: too ..
With C++20, it is possible to have deduction guidelines generated for an alias template (See section "Deduction for alias templates at https://en.cppreference.com/w/cpp/language/class_template_argument_deduction"). Yet, I could not make them work with aggregate initialization syntax. It looks like in this case the deduction guidelines for the alias is not generated. See this example: #include <array> template <size_t ..
I have a need to compare triplets of doubles that were calculated using different processes which causes them to differ by small amounts but should be considered equivalent. One approach that appears to work is to inherit std::array in such a way that the values can be compared within some delta of each other. This ..
When using aggregate / designated initialization of a struct it is possible to refer to another field like this: #include <stdio.h> int main() { struct { int a; int b; } s = { .a = 3, .b = s.a + 1, }; return 0; } We use s.a in the initialization of s.b. However, ..
Recent Comments