Union, Structs and the Soviet.

#include <stdio.h>


typedef struct
{
  char *leader;
  char *capital;
} Nation;

typedef struct
{
  char *plan_name;
  float time_left;
} Plan;

typedef struct
{
  Plan   five_plan;
  Nation republic;
} Union;

int
main (void)
{
  Union soviet;

  soviet.five_plan.time_left = 4.7f;
  soviet.five_plan.plan_name = "The great steelovertake";
  soviet.republic.leader     = "General Secretary";
  soviet.republic.capital    = "Moscow";

  printf ("Remaining: %.1f years\n", soviet.five_plan.time_left);
  printf ("What:      %s\n", soviet.five_plan.plan_name);
  printf ("Leader:    %s\n", soviet.republic.leader);
  printf ("Capital:   %s\n", soviet.republic.capital);

  return 0;
}

#include <stdio.h>


typedef struct {
  const char *plan_name;
  float time_left;
} plan_t;

typedef struct {
  const char *leader;
  const char *capital;
} nation_t;

typedef enum { KPLAN, KNATION } Kind;

typedef struct {
  Kind kind;
  union {
    plan_t  plan;
    nation_t  nation;
  } u;
} Record;

int main(void) {
  Record r1 = { .kind = KPLAN, .u.plan = { "The great steelovertake", 4.7f } };
  Record r2 = { .kind = KNATION, .u.nation = { "General Secretary", "Moscow" } };

  if (r1.kind == KPLAN) {
    printf("plan_t: %s, %.1f years left\n", r1.u.plan.plan_name, r1.u.plan.time_left);
  }
  if (r2.kind == KNATION) {
    printf("nation_t: %s, capital %s\n", r2.u.nation.leader, r2.u.nation.capital);
  }
}