Use callback functions to implement generic algorithms

Another typical function of callback functions is to implement generic algorithms similar to C ++. Such as the implementation of qsort.

The following is a generic function that I write using the features of the callback function. This function is used to find its maximum value among any group of objects. This object can be of the char type, it can also be int ...... let's just look at the program:

 

# Include <stdio. h>

 

Typedef int (* cmp_t) (void *, void *);

 

/* Callback function 1: Compares char objects */

Int cmp_char_data (void * a, void * B)

{

Char para1 = * (char *) );

Char para2 = * (char *) B );

If (para1> para2)

Return 1;

Else if (para1 = para2)

Return 0;

Else

Return-1;

}

 

/* Callback function 2: Compares int objects */

Int cmp_int_data (void * a, void * B)

{

Int para1 = * (int *) );

Int para2 = * (int *) B );

If (para1> para2)

Return 1;

Else if (para1 = para2)

Return 0;

Else

Return-1;

}

 

/* Callback function 3: Compares double objects */

Int cmp_double_data (void * a, void * B)

{

Double para1 = * (double *) );

Double para2 = * (double *) B );

If (para1> para2)

Return 1;

Else

Return-1;

}

 

/* Callback function 4: Compare struct objects */

Typedef struct student

{

Char * Name;

Int score;

} Student_t;

 

Int cmp_struct_data (void * a, void * B)

{

Student_t * para1 = (student_t *);

Student_t * para2 = (student_t *) B;

If (para1-> score> para2-> score)

Return 1;

Else if (para1-> score = para2-> score)

Return 0;

Else

Return-1;

}

 

/* Implement function max */

Void * max (void * data, int num, int size, cmp_t CMP)

{

Void * temp = data;

Int I;

For (I = 1; I <num; I ++)

{

If (CMP (temp, Data + size * I) <0)

{

Temp = Data + size * I;

}

}

Return temp;

}

 

/* Main function */

Int main ()

{

Char c_data [5] = {'A', 'n', 'k', 'P', 'C '};

Int I _data [5] = {1, 20, 50,300, 12 };

Double d_data [5] = {20.2, 130.5, 100.12, 200.23, 45.6 };

Student_t st_data [5] = {"stu1", 56 },{ "stu1", 85 },{ "stu1", 65 },{ "stu1", 96 }, {"stu1", 72 }};

Char max1 = * (char *) max (c_data, 5, sizeof (char), cmp_char_data ));

Int max2 = * (int *) max (I _data, 5, sizeof (INT), cmp_int_data ));

Double max3 = * (double *) max (d_data, 5, sizeof (double), cmp_double_data ));

Student_t * max4 = (student_t *) max (st_data, 5, sizeof (student_t), cmp_struct_data );

Printf ("% C \ t % d \ t % lf \ t % d \ n", max1, max2, max3, max4-> score );

Getchar ();

Return 0;

}

Conversion from http://hi.baidu.com/s_rlzheng/blog/item/ee99512a6cf145315243c1e4.html#0)