L-24 MCS 275 Mon 5 Mar 2001

Below are the listings of the program we discussed in class:

/* L-24 MCS 275 Mon 5 Mar 2001 cross-referential structures */

#include <stdio.h>

struct person
{
   char *name;
   int  age;
   struct home *h;
};

struct home
{
   char *street;
   int  number,zip;
   char *city;
   struct person *p;
};

int main()
{
   struct person bob;
   struct home bobsplace;

   bob.name = "Bob";
   bob.age = 54;
   bob.h = &bobsplace;

   bobsplace.street = "12th ST";
   bobsplace.number = 23;
   bobsplace.city = "Chicago";
   bobsplace.zip = 60607;
   bobsplace.p = &bob;

   printf("Street where %s lives is %s.\n", bob.name, bob.h->street );
   printf("Name of person living in %s %d is %s.\n",
           bobsplace.street, bobsplace.number, bobsplace.p->name);

   return 0;
}

Here is the same program, but now with typedefs :

/* L-24 MCS 275 Mon 5 Mar 2001 cross-referential structures */

#include <stdio.h>

typedef struct person PERSON;
typedef struct home   HOME;

struct person
{
   char *name;
   int  age;
   HOME *h;
};

struct home
{
   char *street;
   int  number,zip;
   char *city;
   PERSON *p;
};

int main()
{
   PERSON bob;
   HOME   bobsplace;

   bob.name = "Bob";
   bob.age = 54;
   bob.h = &bobsplace;

   bobsplace.street = "12th ST";
   bobsplace.number = 23;
   bobsplace.city = "Chicago";
   bobsplace.zip = 60607;
   bobsplace.p = &bob;

   printf("Street where %s lives is %s.\n", bob.name, bob.h->street );
   printf("Name of person living in %s %d is %s.\n",
           bobsplace.street, bobsplace.number, bobsplace.p->name);

   return 0;
}

And here is a modification, where the home contains pointers to several people living there:

/* L-24 MCS 275 Mon 5 Mar 2001 cross-referential structures */

#include <stdio.h>
#include <stdlib.h>

typedef struct person PERSON;
typedef struct home   HOME;

struct person
{
   char *name;
   int  age;
   HOME *h;
};

struct home
{
   char *street;
   int  number,zip;
   char *city;
   int  size;
   PERSON *p;
};

int main()
{
   struct person bob,anna;
   struct home bobsplace;
   int i;

   bob.name = "Bob";
   bob.age = 24;
   bob.h = &bobsplace;
   anna.name = "Anna";
   anna.age = 23;
   anna.h = &bobsplace;

   bobsplace.street = "12th ST";
   bobsplace.number = 23;
   bobsplace.city = "Chicago";
   bobsplace.zip = 60607;
   bobsplace.size = 2;
   bobsplace.p = (PERSON*)calloc(2,sizeof(PERSON));
   bobsplace.p[0] = bob;
   bobsplace.p[1] = anna;

   printf("Street where %s lives is %s.\n", bob.name, bob.h->street );
   printf("Numbers of persons living in %s %d : %d.\n",
           bobsplace.street, bobsplace.number, bobsplace.size);
   printf("Names of persons living there : \n");
   for (i = 0; i < bobsplace.size; i++)
      printf("  %s\n", bobsplace.p[i].name);

   return 0;
}

All of this leads to self-referential structures:

/* L-24 MCS 275 Mon 5 Mar 2001 self-referential structures */

#include <stdio.h>

typedef struct list LIST;

struct list
{
   int  head;
   LIST *tail;
};

int main()
{
   LIST a,b,c;

   a.head = 1;       /* filling in the data */
   b.head = 2;
   c.head = 3;

   printf("Elements in the list : %d %d %d.\n",
          a.head, b.head, c.head);

   a.tail = &b;      /* making the links in the list */
   b.tail = &c;
   c.tail = NULL;

   printf("Elements in the list : %d %d %d.\n",
          a.head, a.tail->head, a.tail->tail->head );

   return 0;
}