错误：没有匹配的函数来调用[…]注意：模板参数推导/替换失败

Question

template <int dim = 2>
class point {
private:
    std::array<double, dim> coords;
public:
    /* Constructors, destructor, some members [...] */
    template <typename operation_aux, int dim_aux> point<dim_aux>
        plus_minus_helper(const point<dim_aux>& op1, const point<dim_aux>& op2);
};

template <typename operation, int dim> point<dim>
    plus_minus_helper(const point<dim>& op1, const point<dim>& op2)
{
    /* Do all the calculations.
     * The algorithm is very similar for both addition and subtraction,
     * so I'd like to write it once
     */
}

template <int dim>
    point<dim> operator+(const point<dim>& op1, const point<dim>& op2)
{
    return plus_minus_helper<std::plus>(op1, op2);
}

template <int dim>
    point<dim> operator-(const point<dim>& op1, const point<dim>& op2)
{
    return plus_minus_helper<std::minus>(op1, op2);
}

int main(int argc, char * argv []) {
    point<2> Pt1(1, 2), Pt2(1, 7), Pt3(0, 0);

    Pt3 = Pt1 + Pt2;
    std::cout << Pt3(0) << " " << Pt3(1) << std::endl;
}

Compiling this code on GCC produces the following error

./test.cpp: In instantiation of ‘point<dim> operator+(const point<dim>&, const point<dim>&) [with int dim = 2]’:
./test.cpp:47:17:   required from here
./test.cpp:35:49: error: no matching function for call to ‘plus_minus_helper(const point<2>&, const point<2>&)’
     return plus_minus_helper<std::plus>(op1, op2);
                                                 ^
./test.cpp:35:49: note: candidate is:
./test.cpp:26:5: note: template<class operation, int dim> point<dim> plus_minus_helper(const point<dim>&, const point<dim>&)
     plus_minus_helper(const point<dim>& op1, const point<dim>& op2)
     ^
./test.cpp:26:5: note:   template argument deduction/substitution failed:

It seems it is a problem with the instatiaton of the template, in fact the - operator does not produce any error. I provided all the necessary types to instantiate the function, an operation and the dimension of the operators. The dimension is implicit in the parameters, and I don't think I passed conflicting parameters.
I'm trying to call the helper function passing to it the calculation to execute (addition or subtraction). I don't want to write the algorithm twice one time for addition and one time for subtraction, because they only differ by for the operation performed.
How to fix this error?

Answer 1

Problem is, that std::plus / std::minus are template classes. You should point, which instantiation of class you want to send, or if you can use C++14 - just <> , if you don't want to point, which instantiation compiler should use you can use template template parameter .

return plus_minus_helper<std::plus<>>(op1, op2);

Live example