funcpointret.c

#include <stdio.h>

union my_result_data {
  int integer;
  float floating;
};

enum my_result_kind {
  MY_RESULT_INTEGER,
  MY_RESULT_FLOATING,
};

struct my_result {
  enum my_result_kind kind;
  union my_result_data data;
};

struct my_result add(int a, int b)
{
  puts("add");
  return (struct my_result){
    .kind = MY_RESULT_INTEGER,
    .data = (union my_result_data){.integer = a+b},
  };
}
struct my_result subtract(int a, int b)
{
  puts("subtract");
  return (struct my_result){
    .kind = MY_RESULT_INTEGER,
    .data = (union my_result_data){.integer = a-b},
  };
}
struct my_result funny(int a, int b)
{
  puts("funny");
  return (struct my_result){
    .kind = MY_RESULT_FLOATING,
    .data = (union my_result_data){.floating = 1.0/(a*b)},
  };

  struct my_result r = {
    .kind = MY_RESULT_FLOATING,
    .data = (union my_result_data){.floating = 1.0/(a*b)},
  };

  struct my_result r;
  r.kind = MY_RESULT_FLOATING;
  r.data = (union my_result_data){.floating = 1.0/(a*b)};
}
int result;
int main()
{
  // Now declaring the array of function pointers
  struct my_result (*function_pointer[])(int, int) = {&add, &subtract, &funny};
  unsigned int choice = 0; int a=15, b=6;
  scanf(">%ud", &choice);
  if(choice>2) return 0;

  struct my_result result = (*function_pointer[choice])(a, b);
  switch (result.kind) {
    case MY_RESULT_INTEGER:
      printf("result was an integer: %d\n", result.data.integer);
      break;
    case MY_RESULT_FLOATING:
      printf("result was a floating: %f\n", result.data.floating);
      break;
    default:
      printf("I don't know what result was ...\n");
      break;
  }
  return 0;
}