C pointer 3-function pointer

Function pointer

Is a pointer to a function, which can be defined as follows:

INT (* pfunc) (INT, INT );

This statement is interpreted as follows:

First (* pfunc), so pfunc is a pointer;

In another explanation (INT, INT), pfunc points to a function. There are two parameters of this function, both of which are integer;

Finally, return value.

Therefore, if a function int max (int A, int B) is defined, we can use the function pointer as follows:

Pfunc = max; // note the return types of the two, which must be consistent.

Function pointers are different from pointer functions. The latter is a function, and its return value is a pointer, such
Char * index (const char * s, int
C );

INT (* max) (int A, int B); // function pointer

Int * max (int A, int B); // pointer Function

The following code is used for function pointers:

(1)

Int min (int A, int B) {return A> B? B: A;} int max (int A, int B) {return A> B? A: B;} int main () {int A = 12; int B = 34; int (* pfunc) (INT, INT ); // define a function pointer pfunc = min; printf ("min = % d/N", pfunc (A, B); pfunc = max; printf ("max = % d/N", pfunc (A, B); int (* P [2]) (INT, INT); P [0] = min; P [1] = max; printf ("min = % d/N", P [0] (a, B); printf ("max = % d/N ", P [1] (a, B); # define ABC minprintf ("min = % d/N", ABC (a, B )); # define EFG maxprintf ("max = % d/N", EFG (A, B); Return 0 ;}

INT (* P [2]) (INT, INT) is a function pointer array. The function pointer feels similar to # define. See the # define section in the code above.

(2)

Typedef struct point {Double X; Double Y;} Point; int CMP1 (void * a, void * B) {int * c = (int *); int * D = (int *) B; return * C-* D;} int cmp2 (void * a, void * B) {double * c = (double *); double * D = (double *) B; Double E = * C-* D; If (E> 0) return 1; else if (E <0) Return-1; else return 0;} int cmp3 (void * a, void * B) {return strcmp (char *) A, (char *) B );} int cmp4 (void * a, void * B) {point * c = (point *) A; point * D = (Point *) B; Double E = C-> X-D-> X; If (E> 0) return 1; else if (E <0) Return-1; else return 0;} void test (void * a, int N, int size, INT (* p) (void *, void *) {void * P1 =; void * P2 = a + size; // do somethingprintf ("% d/N", P (P1, P2);} int main () {int C [2]; c [0] = 12; C [1] = 34; test (C, 2, sizeof (INT), CMP1); double d [2]; d [0] = 1.2, d [1] = 3.4; test (D, 2, sizeof (double), cmp2 ); char s [2] [16] = {"Xiao", "she "}; Test (S, 2, sizeof (s [0]), cmp3); point PT [2]; Pt [0]. X = 1.8; Pt [0]. y = 1.3; Pt [1]. X = 1.4; Pt [1]. y = 1.5; test (PT, 2, sizeof (point), cmp4); Return 0 ;}in example (2), one of the test functions is a function pointer, call different comparison functions to process different types of data.

Is it similar to qsort?