我代碼是這樣的: #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 << "輸入兩個整數(以空格區分):"; cin >> a.x >> a.y; z = (a.x + a.y) * k; z = result(z, b); cout << "計算結果如下:" << endl; cout << "((" << a.x  << " + " << a.y << " ) * " << k << ")+" << b          << "=" << z          << endl; return 0; } 但是報錯了:Scanning dependencies of target cpp[ 50%] Building CXX object CMakeFiles/cpp.dir/main.cpp.o[100%] Linking CXX executable cppUndefined symbols for architecture x86_64:"result(int, int)", referenced from:_main in main.cpp.old: symbol(s) not found for architecture x86_64collect2: error: ld returned 1 exit statusmake[3]: *** [cpp] Error 1make[2]: *** [CMakeFiles/cpp.dir/all] Error 2make[1]: *** [CMakeFiles/cpp.dir/rule] Error 2make: *** [cpp] Error 2