函数指针

t函数指针声明如下：

double (*pf) (int);                 //pt points to a function that takes one int argument and that returns type double

提示：通常，要声明指向特定类型的函数的指针，可以首先编写这种函数的原型，然后用(*pf)替换函数名。这样Pf就是这类函数的指针。

eg：

double pam(int);

double (*pf)(int);

pf=pam;

程序示例：

#include<iostream>
using namespace std;
double betsy(int);
double pam(int);
//second argument is pointer to a type double function that
//takes a type int argument
void estimate(int lines,double(*pf)(int));
int main()
{
    int code;
    cout<<"How many lines of code do you need?";
    cin>>code;
    cout<<"Here are betsy's estimate: ";
    estimate(code,betsy);
    cout<<"Here are pam's estimate: ";
    estimate(code,pam);
    return 0;
}
double betsy(int lns)
{
    return 0.05*lns;
}
double pam(int lns)
{
    return 0.03*lns+0.0004*lns*lns;
}
void estimate(int lines,double(*pf)(int))
{
    cout<<lines<<"lines will take";
    cout<<(*pf)(lines)<<"hour(s) ";
}