CODEWITHSUNDEEP
c++c++11templates
Ch3shire
Ch3shire

Reputation: 1106

C++: template class/function with any number of initializing arguments

I'm trying to create template class of a vector in geometry of arbitrary number of dimensions. I would like to create an intuitive constructor where I can pass number of initializers equal to dimension number. For example:

template<int dim = 3, typename float_t=double> class Vec{
    float_t x[dim];
public:
    Vec(...) {
        //some template magic
    }
};


int main() {
    typedef Vec<3> Vec3d;
    typedef Vec<2> Vec2d;

    double x=1,y=2,z=3;
    Vec3d v(x,y,z);
    Vec2d w(x,y);
}

Now I lack the knowledge of black magic - I mean the C++ templates. How I should write this example to get my goal? Of course I don't want to write every exact constructor for every case, that's not the spirit of C++ templates - and I'm really interested how to accomplish that in the smart way.

Upvotes: 2

Views: 171

Answers (1)

O&#39;Neil
O&#39;Neil

Reputation: 3849

You need a parameter pack:

template <typename... Args>
Vec(Args... args) : x{args...} {
    static_assert(sizeof...(Args) == dim, "Number of parameters should match dimension");
}

I'm also using static_assert to make sure the user enters the right number of parameters matching the dimension.

Upvotes: 6

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