学习c++的新手遇到问题,求大神帮个忙

Question

我代码是这样的:
#include <iostream>
using namespace std;
int result(int, int);
const int k = 2;
struct  Point{
    int x , y;
};

int main() {
    int z(0), b(50);
Point a;
cout << "输入两个整数(以空格区分):";
cin >> a.x >> a.y;

z = (a.x + a.y) * k;
z = result(z, b);
cout << "计算结果如下:" << endl;
cout << "((" << a.x  << " + " << a.y
<< " ) * " << k << ")+" << b
         << "=" << z
         << endl;
return 0;
}
但是报错了:

Scanning dependencies of target cpp
[ 50%] Building CXX object CMakeFiles/cpp.dir/main.cpp.o
[100%] Linking CXX executable cpp
Undefined symbols for architecture x86_64:
"result(int, int)", referenced from:
_main in main.cpp.o
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status
make[3]: *** [cpp] Error 1
make[2]: *** [CMakeFiles/cpp.dir/all] Error 2
make[1]: *** [CMakeFiles/cpp.dir/rule] Error 2
make: *** [cpp] Error 2

Answer 1

你 result 函数定义呢？只有声明没有定义，怎么调用