函数符

 1 int add(int a, int b)
 2 {
 3     return (a + b);
 4 }
 5 
 6 int main()
 7 {
 8     int a = 100, b = 200;
 9     int c = add(a, b);  // add，即函数名，为函数符一种范畴
10     return 0;
11 }

 1 int add(int a, int b)
 2 {
 3     return (a + b);
 4 }
 5 
 6 int main()
 7 {
 8     typedef int(*funcPtr)(int, int);
 9     funcPtr fpAdd = add;
10 
11     int a = 100, b = 200;
12     int c = fpAdd(a, b);  // fpAdd，即函数指针的对象，为函数符的另一种范畴
13     return 0;
14 }

 1 #include <iostream>
 2 
 3 class Linear
 4 {
 5 
 6 private:
 7     double slope;
 8     double y0;
 9 public:
10     //构造函数
11     Linear(double sl_ = 1, double y_ = 0) :slope(sl_), y0(y_) {}
12     //重载()运算符
13     double operator()(double x)
14     {
15         return (y0 + slope * x);
16     }
17 };
18 
19 int main()
20 {
21     Linear f1;
22     Linear f2(2.5, 10.0);
23 
24     //在此处Linear类的对象f1和f2利用重载的（）运算符以函数的方式实现了 y0 +slope*x 功能
25     //因此f1和f2可以成为函数符（或函数对象）的另一种范畴
26     double y1 = f1(12.5);
27     double y2 = f2(0.4);
28 
29     std::cout << "y1: " << y1 << std::endl; // 0 + 12.5 * 1 = 12.5
30     std::cout << "y2: " << y2 << std::endl; // 10.0 + 2.5 * 0.4 = 11
31 
32     return 0;
33 }