c++ - 通过将模板作为参数传递来简化模板函数？

Question

我写了一个小例子来说明这个问题。 solve_bs1_y 和 solve_bs2_y 的实现完全相似。唯一的区别是函数调用:solve_bs*_z。不幸的是，似乎不可能将模板作为参数传递来替换 solve_bs*_z 的函数调用。因此，我必须为每个 solve_bs*_z 实现另一个 solve_bs*_y。有没有一种方法可以简化代码，以便我只需要 solve_bs_y 的一个实现？

// Example program
#include <iostream>
#include <string>

template <int x, int y, int offs, class T>
float solve_bs1_z(T mat, float fS, float fT, float fU) {
  return 1; // to keep it simple
}

template <int x, int y, int offs, class T>
float solve_bs2_z(T mat, float fS, float fT, float fU) {
  return 2; // to keep it simple
}

// essentially the same as solve_bs2_y
template <int x, int offs, class T>
float solve_bs1_y(T mat, float fS, float fT, float fU) {
  const float bs_s = 2;

  return    ( solve_bs1_z<x, 0, offs>(mat, fS, fT, fU)
      + solve_bs1_z<x, 1, offs>(mat, fS, fT, fU)
      + solve_bs1_z<x, 2, offs>(mat, fS, fT, fU))
      * bs_s;
}
// essentially the same as solve_bs1_y
template <int x, int offs, class T>
float solve_bs2_y(T mat, float fS, float fT, float fU) {
  const float bs_s = 2;

  return    ( solve_bs2_z<x, 0, offs>(mat, fS, fT, fU)
      + solve_bs2_z<x, 1, offs>(mat, fS, fT, fU)
      + solve_bs2_z<x, 2, offs>(mat, fS, fT, fU) )
      * bs_s;
}

// these are called in the program ..
template<int offs, class T>
float solve_ffd_bs1(T mat, float fS, float fT, float fU) {
  return    solve_bs1_y<0, offs>(mat, fS, fT, fU) +
      solve_bs1_y<1, offs>(mat, fS, fT, fU) +
      solve_bs1_y<2, offs>(mat, fS, fT, fU);
}

template<int offs, class T>
float solve_ffd_bs2(T mat, float fS, float fT, float fU) {
  return    solve_bs2_y<0, offs>(mat, fS, fT, fU) +
      solve_bs2_y<1, offs>(mat, fS, fT, fU) +
      solve_bs2_y<2, offs>(mat, fS, fT, fU);
}


int main()
{
    int mat[3][3][3] = {
        {{1,2,3}, {4,5,6}, {7,8,9}},
        {{11,2,3}, {14,5,6}, {17,8,9}},
        {{21,2,3}, {24,5,6}, {27,8,9}}
        };


  solve_ffd_bs2<0>(mat, 1,2,3);

  return 0;
}

Answer 1

没有结构模板的包装器版本:

struct s1 {
    template <int x, int y, int offs, class T>
    static float solve_bs_z(T mat, float fS, float fT, float fU) {
      return 1; // to keep it simple
    }
};

struct s2 {
    template <int x, int y, int offs, class T>
    static float solve_bs_z(T mat, float fS, float fT, float fU) {
      return 2; // to keep it simple
    }
};

template <class Wrapper, int x, int offs, class T>
float solve_bs_y(T mat, float fS, float fT, float fU) {
  const float bs_s = 2;

  return    ( Wrapper::template solve_bs_z<x, 0, offs>(mat, fS, fT, fU)
      + Wrapper::template solve_bs_z<x, 1, offs>(mat, fS, fT, fU)
      + Wrapper::template solve_bs_z<x, 2, offs>(mat, fS, fT, fU))
      * bs_s;
}

然后调用:

solve_bs_y<s1, 0, 1>(...);