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;
}