C++ 定义函数指针

来源：https://www.geeksforgeeks.org/function-pointer-in-cpp/

return_type (*FuncPtr) (parameter type, ....);

// Declaring
return_type (*FuncPtr) (parameter type, ....); 

// Referencing
FuncPtr= function_name;

// Dereferencing
data_type x=*FuncPtr;