ex6_54_55_56.cpp

// @Yue Wang
//
// Exercise 6.54:
// Write a declaration for a function that takes two int
// parameters and returns an int, and declare a vector whose
// elements have this function pointer type.
//
// Exercise 6.55:
// Write four functions that add, subtract, multiply, and divide
// two int values. Store pointers to these functions in your
// vector from the previous exercise.
//
// Exercise 6.56:
// Call each element in the vector and print their result.
//

#include <iostream>
#include <string>
#include <vector>
using std::vector; using std::cout;

//
// @brief Exercise 6.54
// @note  define the function type fp
//
inline int f(const int, const int);
typedef decltype(f) fp;//fp is just a function type not a function pointer

//
// @brief Exercise 6.55
// @note  Store pointers to these functions in the vector
//
inline int NumAdd(const int n1, const int n2)  { return n1 + n2; }
inline int NumSub(const int n1, const int n2)  { return n1 - n2; }
inline int NumMul(const int n1, const int n2)  { return n1 * n2; }
inline int NumDiv(const int n1, const int n2)  { return n1 / n2; }

vector<fp*> v{ NumAdd, NumSub, NumMul, NumDiv };

int main()
{
    //
    // @brief Exercise 6.56
    // @note  Call each element in the vector and print their result.
    //
    for (auto it = v.cbegin(); it != v.cend(); ++it)
        cout << (*it)(2, 2) << std::endl;

    return 0;
}