将大括号括起来的初始值设定项列表和向量的组合传递给可变参数模板

Question

我想编写一个

table

类，它以多列作为参数来创建表。这是我的尝试。

template <typename T = double>
class table
{
private:
    using type = std::remove_reference_t<std::remove_cv_t<T>>;
    static_assert(std::is_arithmetic_v<type>);
    using coltype = std::vector<type>;

    std::vector<coltype> m_data;

public:
    template <typename... Args>
    table(Args &&...args)
    {
        static_assert(sizeof...(args) >= 2);
        static_assert((std::is_constructible_v<coltype, Args &&> && ...));
        (m_data.push_back(std::forward<Args>(args)), ...);
    }
    ~table() = default;
    
    // ... other stuff
};

但是，目前这不适用于大括号括起来的初始值设定项列表。我打算按如下方式使用它：

std::vector<double> vec1{1.,2.,3.};
std::vector<double> vec2{4.,5.,6.};
table t1(vec1,vec2); //works
table t2({1.,2.,3.},{4.,5.,6.}); //doesn't compile as brace-enclosed initializers doesn't have a type
table t3({1,2,3},vec1,vec2) // also possibly combinations

如何实现这一目标？是否可以使用

std::initializer_list

进行一些实施？

Answer 1

您似乎想使用

std::initializer list<T>

。

#include <initializer_list>
#include <vector>

template <typename T = double>
class table {
 private:
  using type = std::remove_reference_t<std::remove_cv_t<T>>;
  static_assert(std::is_arithmetic_v<type>);
  using coltype = std::vector<type>;

  std::vector<coltype> m_data;

 public:
  table(std::initializer_list<std::vector<T>> args) { m_data = args; }
  ~table() = default;

  // ... other stuff
};

int main() {
  std::vector<double> vec1{1., 2., 3.};
  std::vector<double> vec2{4., 5., 6.};
  table t1{vec1, vec2};  // works
  table t{{1., 2., 3.}, {4., 5., 6.}};
  table t3{{1, 2, 3}, vec1, vec2};  // also possibly combinations
}