cpp/CPPlusV6/Chapter 7/arfupt.cpp

// arfupt.cpp -- an array of function pointers
#include <iostream>
// various notations, same signatures
const double * f1(const double ar[], int n);
const double * f2(const double [], int);
const double * f3(const double *, int);

int main()
{
    using namespace std;
    double av[3] = {1112.3, 1542.6, 2227.9};

    // pointer to a function
    const double *(*p1)(const double *, int) = f1;
    auto p2 = f2;  // C++0x automatic type deduction
    // pre-C++0x can use the following code instead
    // const double *(*p2)(const double *, int) = f2;
     cout << "Using pointers to functions:\n";
    cout << " Address  Value\n";
    cout <<  (*p1)(av,3) << ": " << *(*p1)(av,3) << endl;
    cout << p2(av,3) << ": " << *p2(av,3) << endl;

    // pa an array of pointers
    // auto doesn't work with list initialization
    const double *(*pa[3])(const double *, int) = {f1,f2,f3};
    // but it does work for initializing to a single value
    // pb a pointer to first element of pa
    auto pb = pa;
    // pre-C++0x can use the following code instead
    // const double *(**pb)(const double *, int) = pa;
    cout << "\nUsing an array of pointers to functions:\n";
    cout << " Address  Value\n";
    for (int i = 0; i < 3; i++)
        cout << pa[i](av,3) << ": " << *pa[i](av,3) << endl;
    cout << "\nUsing a pointer to a pointer to a function:\n";
    cout << " Address  Value\n";
    for (int i = 0; i < 3; i++)
        cout << pb[i](av,3) << ": " << *pb[i](av,3) << endl;

    // what about a pointer to an array of function pointers
    cout << "\nUsing pointers to an array of pointers:\n";
    cout << " Address  Value\n";
    // easy way to declare pc 
    auto pc = &pa; 
     // pre-C++0x can use the following code instead
    // const double *(*(*pc)[3])(const double *, int) = &pa;
   cout << (*pc)[0](av,3) << ": " << *(*pc)[0](av,3) << endl;
    // hard way to declare pd
    const double *(*(*pd)[3])(const double *, int) = &pa;
    // store return value in pdb
    const double * pdb = (*pd)[1](av,3);
    cout << pdb << ": " << *pdb << endl;
    // alternative notation
    cout << (*(*pd)[2])(av,3) << ": " << *(*(*pd)[2])(av,3) << endl;
    // cin.get();
    return 0;
}

// some rather dull functions

const double * f1(const double * ar, int n)
{
    return ar;
}
const double * f2(const double ar[], int n)
{
    return ar+1;
}
const double * f3(const double ar[], int n)
{
    return ar+2;
}