error: no matching function for call to [...] note: template argument deduction/substitution failed

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;
}

在 GCC 上编译此代码会产生以下错误

./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:

貌似是模板初始化的问题，实际上-操作符并没有报错。我提供了所有必要的类型来实例化函数、操作和运算符的维度。尺寸隐含在参数中，我不认为我传递了冲突的参数。
我正在尝试调用传递给它的辅助函数来执行计算（加法或减法）。我不想将算法写两次，一次用于加法，一次用于减法，因为它们仅在执行的操作上有所不同。
如何修复此错误？

Answer 1

问题是，std::plus/std::minus 是模板 class。你应该指出，你想发送 class 的哪个实例化，或者如果你可以使用 C++14 - 只是 <>，如果你不想指出，你可以使用哪个实例化编译器使用 template template parameter.

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

Live example

error: no matching function for call to [...] note: template argument deduction/substitution failed

error: no matching function for call to [...] note: template argument deduction/substitution failed

c++

templates

c++11

instantiation