CODEWITHSUNDEEP
c++
Hugo
Hugo

Reputation: 13

How to fix missing default argument on parameter 'args' with clang?

I have a short and convenient code for multi-dimensional vectors, with the ability to choose size and default value during initialization.

#include <iostream>
#include <vector>
using std::vector;

template<int D, typename T>
struct Vec : public vector<Vec<D - 1, T>> {
    static_assert(D >= 1, "Vector dimension must be greater than zero!");
    template<typename... Args>
    Vec(int n = 0, Args... args) : vector<Vec<D - 1, T>>(n, Vec<D - 1, T>(args...)) {}
};
template<typename T>
struct Vec<1, T> : public vector<T> {
    Vec(int n = 0, const T& val = T()) : vector<T>(n, val) {}
};

int main() {
    int nbRow, nbCol;
    std::cin >> nbRow >> nbCol;
    Vec<2, int> grid(nbRow, nbCol, 0);
}

It works with GCC, but not with clang 10.0.0 (standard c++17 or gnu++17, both don't work).

main.cpp:15:25: error: missing default argument on parameter 'args'
        Vec(int n = 0, Args... args) : vector<Vec<D - 1, T>>(n, Vec<D - 1, T>(args...)) {}
                               ^
main.cpp:30:14: note: in instantiation of function template specialization 'Vec<2, int>::Vec<int, int>' requested here
        Vec<2, int> grid(nbRow, nbCol, 7);
                    ^
main.cpp:15:25: error: missing default argument on parameter 'args'
        Vec(int n = 0, Args... args) : vector<Vec<D - 1, T>>(n, Vec<D - 1, T>(args...)) {}

Is there a simple way to fix this? Thanks in advance!

Upvotes: 1

Views: 2170

Answers (1)

Mooing Duck
Mooing Duck

Reputation: 66991

int n = 0 an argument with a default value can't be followed by arguments without defaults. Remove the =0

Upvotes: 4

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