0. Function pointers are among the most powerful tools in C. It can be used to implement function callback in C. C++ takes a slightly different route for callbacks.
1. Function pointer
// (1)define a function
bool lengthCompare(const string&, const string&){
return true;
}
// (2)define a function pointer and initialize it
bool (*pf) (const string&, const string&);
pf = lengthCompare;
// (3)call a function through a function pointer
cmpFcn pf = lengthCompare; // initialize the pf
pf("hi","bye"); // implicitly dereferenced
(*pf)("hi","type"); // explicitly dereferenced
// (4)define a type named cmpFcn, this type is a pointer to function.
typedef bool (*cmpFcn) (const string&, const string&);
typedef int func(int*, int); // func is a function type, not a pointer to a function.
// (5)function pointer as a parameter
void useBigger(const string&, const string&, bool (*)(const string&, const string&));
void useBigger(const string&, const string&, bool (const string&, const string&));
// (6)function pointer as a return type
int (*ff(int))(int*, int); // is the same as following codes
typedef int (*pf)(int&, int);
pf ff(int); // ff return a pointer to function
// (7) example
int main(){
cmpFcn pf1;
cmpFcn pf2 = 0;
cmpFcn pf3 = lengthCompare;
cmpFcn pf4 = &lengthCompare;
pf = lengthCompare;
cout << pf << endl; // 1
cout << pf1 << endl; // 0
cout << pf2 << endl; // 0
cout << pf3 << endl; // 1
cout << pf4 << endl; // 1
return 0;
}
2. There is no conversation between one pointer to function type and another.
A function pointer must point to the function whose type is exactly the same as this pointer points to.
( Most of the code are coming from C++ primer fourth edition )
原文地址：https://www.cnblogs.com/sarah-zhang/p/12210931.html