A series of tests of function pointers in C language

1. Start with a simple summation-quadrature function

#include <stdio.h>int Add (int a, int b) {    return a + b;} int mul (int a, int b) {    return a * b;} int main () {    int a_count = Add (5,7);    int m_count = Mul (5,7);    printf ("A_count is%d\n", a_count);    printf ("M_count is%d\n", m_count);        return 0;}

Output:

A_count is 12

M_count is 35

Program ended with exit code:0

2. Try the function pointer

#include <stdio.h>int Add (int a, int b) {    return a + b;} int mul (int a, int b) {    return a * b;} int main () {    int (*p_add) (int,int);//Declare function pointer    p_add = add;    Int (*p_mul) (int,int);    P_mul = Mul;        int a_count = P_add (5,7);    int m_count = P_mul (5,7);    printf ("A_count is%d\n", a_count);    printf ("M_count is%d\n", m_count);        return 0;}

The result is the same

A_count is 12

M_count is 35

Program ended with exit code:0

3. Simplify the definition of function pointers

#include <stdio.h>int Add (int a, int b) {    return a + b;} int mul (int a, int b) {    return a * b;} int main () {    typedef int (*fun) (int,int);//definition type fun is a pointer to a function fun    p_add = add;    Fun P_mul = Mul;        int a_count = P_add (5,7);    int m_count = P_mul (5,7);    printf ("A_count is%d\n", a_count);    printf ("M_count is%d\n", m_count);        return 0;}

The result is the same

A_count is 12

M_count is 35

Program ended with exit code:0

4. Try using a function pointer array

#include <stdio.h>int Add (int a, int b) {    return a + b;} int mul (int a, int b) {    return a * b;} int main () {    int (*func[]) (int,int) = {add,mul};//Defines the function pointer array        int a_count = func[0] (5,7);    int m_count = func[1] (5,7);    printf ("A_count is%d\n", a_count);    printf ("M_count is%d\n", m_count);        return 0;}

The result is the same

A_count is 12

M_count is 35

Program ended with exit code:0

5. Improved function pointer array

After all, after the function is more, who can remember multiplication is in the array of the first few, subscript that is how much.

#include <stdio.h>int Add (int a, int b) {    return a + b;} int mul (int a, int b) {    return a * b;} int main () {    int (*func[]) (int,int) = {add,mul};//definition function pointer array    enum func_tpye{add, mul};  The order is aligned with the above        int a_count = Func[add] (5,7);    int m_count = Func[mul] (5,7);        printf ("A_count is%d\n", a_count);    printf ("M_count is%d\n", m_count);        return 0;}

The result is the same

A_count is 12

M_count is 35

Program ended with exit code:0

6. Adjust the different functions in the function

In the previous example, directly using a function would be better with some

#include <stdio.h>typedef  Int (*fun) (int,int); int add (int a, int b) {    return a + b;} int mul (int a, int b) {    return a * b;} int Add_mul (fun f,int a,int b) {    return F (A, b);} int main () {    int (*func[]) (int,int) = {add,mul};//definition function pointer array    enum func_tpye{add, mul};  The order is aligned with the above        printf ("A_count is%d\n", Add_mul (Func[add], 5, 7));    printf ("M_count is%d\n", Add_mul (Func[mul], 5, 7));    return 0;}

The result is the same

A_count is 12

M_count is 35

Program ended with exit code:0

7. The above example can be expanded more strongly

For example, multiply the two-number multiplication to multiply the number multiplied by the sum

#include <stdio.h> #include <stdarg.h>typedef  int (*fun) (int,int), int add (int a, int b) {    return a + b ;} int mul (int a, int b) {    return a * b;} int Add_mul (fun f,int n,...) {    va_list ap;    Va_start (ap,n);    int count = Va_arg (AP, int);    for (int i = 0; i< (n-1); ++i) {        count = f (Count,va_arg (AP, int));    }    return count;} int main () {    int (*func[]) (int,int) = {add,mul};//definition function pointer array    enum func_tpye{add, mul};  The order is aligned with the above        printf ("A_count is%d\n", Add_mul (Func[add], 5,1,2,3,4,5));    printf ("A_count is%d\n", Add_mul (Func[add], 3,7,3,6));        printf ("M_count is%d\n", Add_mul (Func[mul], 5,1,2,3,4,5));    printf ("M_count is%d\n", Add_mul (Func[mul], 3,7,3,6));    return 0;}

The first parameter is a function function, the second argument is the number of operations, followed by an indeterminate parameter.

The result is:

A_count is 15

A_count is 16

M_count is 120

M_count is 126

Program ended with exit code:0

A series of tests of function pointers in C language