Function pointers, function pointers, and pointer Functions

Function pointers, function pointers, and pointer Functions

1. Use of function pointers

Int fun (int a, int B); // declare a function int (* p) (int, int) // define a function pointer, p is a function pointer, the int at the beginning refers to the return value type of the function, followed by the return value type of the function in brackets // assign a value to the function pointer p = fun; // p points to the function p = & fun; // and p = fun are equivalent. // Several equivalent forms of function call int a = p (1, 2 ); int B = (* p) (1, 2); int c = fun (1, 2 );

2. Several Forms of function pointer Definition

Defines the function pointer pointing to int fun (int a, int B ).

1) direct definition:

Int (* p) (int, int );

P = fun; // or p = & fun

2) use typedef to define the type alias:

// P1, p2 is a function pointer type

Typedef int (* p1) (int, int );

Typedef decltype (fun) * p2;

P1 f1 = fun; // here p1 is a function pointer type. You need to define a specific function pointer object f, and f is a pointer to the function.

P2 f2 = fun; // same as above

// Here, p1 and p2 are function types,

Typedef int p1 (int, int );

Typedef decltype (fun) p2;

P1 * f1 = fun; // f1 is a function pointer

P2 * f2 = fun; // f2 is a function pointer

3) use using to define the type alias

Using p1 = int (*) (int, int); // p1 is a function pointer type.

Using p2 = int (int, int); // p2 is a function type.

P1 f1 = fun; // f1 is a function pointer

P2 * f2 = fun; // f2 is a function pointer

3. function pointer Parameters

1) The function name is used as the form parameter, and the function name is automatically converted to the function pointer.

# Include <iostream> using namespace std; int sum (int a, int B) {return a + B;} void fun (int (* p) (int, int )) {cout <p (2, 3) <endl;} int main (int argc, char * argv []) {fun (sum ); // sum is automatically converted to function pointer return 1 ;}

 

2) define the function type alias

# Include <iostream> using namespace std; int sum (int a, int B) {return a + B;} typedef int f (int, int); void fun (f p) // f is the function type, and the form parameter is automatically converted to the function pointer type {cout <p (2, 3) <endl;} int main (int argc, char * argv []) {fun (sum); // here sum is converted to function pointer return 1 ;}

 

3) define a function pointer alias

# Include <iostream> using namespace std; int sum (int a, int B) {return a + B;} typedef int (* f) (int, int ); void fun (f p) // f is the function pointer type, and p is the function pointer {cout <p (2, 3) <endl;} int main (int argc, char * argv []) {fun (sum); // sum is automatically converted to function pointer return 1 ;}

4. returns the pointer to the function.

1) define directly

Int (* f (int) (int, int) // f (int) Is the function name and parameter list, and the return value type is int (*) (int, int)

2) Adopt the tail Return Method

auto f(int)->int(*)(int,int)                

3) Use a type alias to define the function pointer type

Tpyedef int (* p1) (int, int); using p2 = int (*) (int, int); typedef int p3 (int, int ); using p4 = int (int, int); // equivalent declaration p1 f (int); p2 f (int); p3 * f (int); p4 * f (int );