Weitere Beispiele zur "Tier-Datenbank"-Aufgabe

20221212/tier-datenbank-15.c

+#include <stdio.h>
+#include <stdlib.h>
+
+#define ANIMAL     0
+#define WITH_WINGS 1
+#define WITH_LEGS  2
+
+typedef struct animal
+{
+  int type;
+  char *name;
+} animal;
+
+typedef struct with_wings
+{
+  int type;
+  char *name;
+  int wings;
+} with_wings;
+
+typedef struct with_legs
+{
+  int type;
+  char *name;
+  int legs;
+} with_legs;
+
+typedef union object
+{
+  animal a;
+  with_wings w;
+  with_legs l;
+} object;
+
+object *new_wings (char *pname, int pwings)
+{
+  object *o = malloc (sizeof (with_wings));
+  o->a.type = WITH_WINGS;
+  o->a.name = pname;
+  o->l.legs = pwings;
+  return o;
+}
+
+object *new_legs (char *pname, int plegs)
+{
+  object *o = malloc (sizeof (with_legs));
+  o->a.type = WITH_LEGS;
+  o->a.name = pname;
+  o->l.legs = plegs;
+  return o;
+}
+
+int main (void)
+{
+  object *a[2] = { new_wings ("duck", 2), new_legs ("cow", 4) };
+
+  for (int i = 0; i < 2; i++)
+    {
+      if (a[i]->a.type == WITH_LEGS)
+        printf ("A %s has %d legs.\n", a[i]->a.name, a[i]->l.legs);
+      else if (a[i]->a.type == WITH_WINGS)
+        printf ("A %s has %d wings.\n", a[i]->a.name,  a[i]->w.wings);
+      else
+        printf ("Error in animal: %s\n", a[i]->a.name);
+    }
+
+  return 0;
+}