使用模板计算向量的平均值

Question

I made a simple function that takes 2 std::array and returns another std::array with the average values of the values in the std::arrays s.

template<typename T, std::size_t N>
std::array<T, N> average(const std::array<T, N>& a1, const std::array<T, N>& a2)
{
    std::array<T, N> array;
    for (std::size_t i = 0; i < N; ++i)
        array[i] = (a1[i] + a2[i]) / 2;

    return array;
}

Works perfectly. Now I would like to calculate the average of N vectors. So I made this

template<typename T, std::size_t N, typename... Ts>
std::array<T, N> average(const Ts&... args)
{
    std::array<T, N> result;
    for (std::size_t i = 0; i < N; ++i)
    {
        T addedValues = 0;
        for (const auto& array : { args... })
            addedValues += array[i];

        result[i] = addedValues / sizeof...(args);
    }

    return result;
}

Which also works, but I have to specify the resulting template arguments

std::array<int, 3> a{ 1, 2, 3 };
std::array<int, 3> b{ 3, 4, 5 };

auto c = average<int, 3>(a, b); //'<int, 3>' not good, possible without?

I couldn't think of another way, can somebody help me please?

Answer 1

Provided that you'd also made the necessary changes in the body of the template function. You could change the signature of your template function as follows:

template<typename T, std::size_t N, typename... Ts>
std::array<T, N> average(std::array<T, N> const &arr, const Ts&... args)

This way you wouldn't have to specify the template arguments explicitly and template argument deduction would deduce T and N and thus you could call your average template function as:

std::array<int, 3> a{ 1, 2, 3 };
std::array<int, 3> b{ 3, 4, 5 };

auto c = average(a, b);