generic example

generics.c

/* generics.c */
#include "generics.h"
void *max(void *data[], int num, cmp_t cmp)
{
  int i;
  void *temp = data[0];
  for(i=1; i<num; i++) {
    if(cmp(temp, data[i])<0)
      temp = data[i];
  }
  return temp;
}

generics.h

/* generics.h */
#ifndef GENERICS_H
#define GENERICS_H
typedef int (*cmp_t)(void *, void *);
extern void *max(void *data[], int num, cmp_t cmp);
#endif

main.c

/* main.c */
#include <stdio.h>
#include "generics.h"

typedef struct {
  const char *name;
  int score;
} student_t;

int cmp_student(void *a, void *b)
{
  if(((student_t *)a)->score > ((student_t *)b)->score)
    return 1;
  else if(((student_t *)a)->score == ((student_t*)b)->score)
    return 0;
  else
    return -1;
}

int main(void)
{
  student_t list[4] = {{"Tom", 68}, {"Jerry", 72},{"Moby", 60}, {"Kirby", 89}};
  
  student_t *plist[4] = {&list[0], &list[1],&list[2], &list[3]};
  
  student_t *pmax = max((void **)plist, 4,cmp_student);
  
  printf("%s gets the highest score %d\n", pmax->name, pmax->score);
  
  return 0;
}