C Language Learning 019: function pointer, language learning 019

C Language Learning 019: function pointer, language learning 019

In C language, the function name is also a pointer variable. For example, when you create an add (int n, int m) function, you also create a pointer variable named add, therefore, we can assign a value to a function pointer as a type and pass it as a parameter.

Formula for creating function pointers in C language:
Return type (* pointer variable) (parameter type)

1 # include <stdio. h> 2 3 int add (int n, int m) {4 return n + m; 5} 6 7 int sub (int n, int m) {8 return n-m; 9} 10 11 int main () {12 int n = 10; 13 int m = 5; 14 int (* calculate) (int, int ); // create a variable named calculate 15 calculate = add; 16 int result = calculate (n, m); // equivalent to add (n, m ); 17 printf ("% I \ n", result); 18 calculate = sub; 19 result = calculate (n, m); // sub (n, m ); 20 printf ("% I \ n", result); 21 return 0; 22}

Although the function pointer is a pointer, when using it, we can omit the "*" statement, such as the calculate (n, m) above. We do not need to write (* calculate) (n, m); it should be noted that the function pointer only accepts the function address that is the same as its return value and parameter.

Function pointer Array

1 # include <stdio. h> 2 3 enum response_type {DUMP, SECOND_CHANCE, MARRIAGE}; 4 typedef struct {5 char * name; 6 enum response_type; 7} response; 8 9 void dump (response r) {10 printf ("dump % s \ n", r. name); 11} 12 13 void second_chance (response r) {14 printf ("second_chance % s \ n", r. name); 15} 16 17 void marriage (response r) {18 printf ("marriage % s \ n", r. name); 19} 20 21 int main () {22 response r [] = {"Mike", DUMP}, {"Luis", SECOND_CHANCE}, {"Matt ", SECOND_CHANCE },{ "William", MARRIAGE }}; 23 void (* replies []) (response) = {dump, second_chance, marriage }; // create a function pointer array 24 int I; 25 for (I = 0; I <4; I ++) {26 replies [r [I]. type] (r [I]); 27} 28 return 0; 29}