Thread: Structures in C Help Please!

Code:

/*      Complex Structures 6 Points

 Define pHead, a pointer to a structure called HEADER.
 This structure contains two fields: a counter (type int)
 and a pointer to an array of structures, called pAry.

 The base type of the pAry array is another structure called BOOK.

 This BOOK structure contains three fields: title (a dynamically allocated string),
 author (30 characters), and date of type DATE (a structure with three integers:
 month, day, and year).

       Requirements:
       1.      Type Definitions
       2.      In main(), define an array of 5 books and initialize it.
       3.      Write printBook(), a function that prints a book:
                 void printBook( const BOOK *p );
       4.      Write a function that prints the array of books using the printBook()
           function in a loop.
       5. Code a printf statement to print
                       - the title,
                       - the first letter of the author's name, and
                       - the year of the third book in the array.

       Save the output as a comment then upload the program.

 Written by:Anastasia Glyantseva
 Date: 6/5/2012

// ====================================================== */
#include <stdio.h>
#include <string.h>
#define MAX_TITLE 100

void printBook( const BOOK *p);

typedef struct
       {
       char title[MAX_TITLE];
       char author[30];
               typedef struct
                {
                       int month;
                       int day;
                       int year;
                }DATE;
       } BOOK;
typedef struct
       {
        int counter = 0;
        char *pAry = *BOOK;
       }HEADER;
int main( void )
{
//  Local definitions
BOOK list[5]=
{
       {"Title1", "Author1", {1, 26, 2001}},
       {"Title2", "Author2", {2, 27, 2002}},
       {"Title3", "Author3", {3, 28, 2003}},
       {"Title4", "Author4", {4, 29, 2004}},
       {"Title5", "Author5", {5, 30, 2005}},
};
//  Statements
       HEADER head = {5, list};
       HEADER *pHead = &head;
       pHead -> pAry[2].title;
       *(pHead -> pAry[2].author);
       pHead->pAry[2].date.year;

return ;
}
void printBook( const BOOK *p)
{


}

-So we just started learning about this stuff in class so chances are, this code is horrible... But I need to finish this assignment(the instructions are the comment portion on the top). Some of the problems that I'm having right now is my compiler not liking all of the braces that I have in my BOOK structure initialization...But I can swear it looks just like that our teacher told us to do. Another problem is the pAry. It tells me that 'HEADER' has no member named pAry. But I don't know how to fix this because I put pAry in HEADER already.
Anyway, thank you for your time and sorry if this code looks really stupid.

I can swear it looks just like that our teacher told us to do

I'm ready to believe that your teacher made a bad mistake, but he didn't tell you to do that with the structure definitions as you've posted them.

I don't know how to fix this because I put pAry in HEADER already.

The `pAry' declaration is invalid. Is a `*BOOK' (Which by the way is itself a meaningless and invalid expression.) a `char *'?

To fix all this crap, start at the top and work your way down. For example, the `DATE' label isn't a variable but a structure definition.

Soma

Originally Posted by phantomotap

I'm ready to believe that your teacher made a bad mistake, but he didn't tell you to do that with the structure definitions as you've posted them.



The `pAry' declaration is invalid. Is a `*BOOK' (Which by the way is itself a meaningless and invalid expression.) a `char *'?

To fix all this crap, start at the top and work your way down. For example, the `DATE' label isn't a variable but a structure definition.

Soma

The *BOOK was a typo. I meant for it to be &BOOK. But this still doesn't not remedy the problem. From what I understand, DATE is supposed to be a structure definition... Honestly, the part with all the braces was copied from what the teacher wrote on the board. Could you tell me what the problems are so that I could have a better chance of fixing them?

O_o

Nope, but if you post the compiler errors you are getting and the latest code that you actually have someone here will be happy to help you understand what the compiler errors say so that you may understand the problems for yourself.

Soma

I already posted the compiler errors... A bunch of them are warnings about the extra braces for BOOK list and the other one is an error that HEADER has no member named pAry. As for the code, beside the change from *BOOK to &BOOK nothing else is really changed cause I'm kind of already stuck with the errors that I have from the code already written.

Originally Posted by phantomotap

To fix all this crap, start at the top and work your way down.

Actually I would start from the bottom and work my way up: first typedef DATE, using this new type to typedef BOOK, ...

Bye, Andreas

Code:

#include <stdio.h>
#include <string.h>
#define MAX_TITLE 100

typedef struct
{
       int month;
       int day;
       int year;
}DATE;
typedef struct
{
       char title[MAX_TITLE];
       char author[30];
       DATE date;
} BOOK;
typedef struct
       {
        int counter;
        BOOK *pAry;
       }HEADER;
void printBook( const BOOK *p);
void printList( const BOOK *p, HEADER *pHead );

int main( void )
{

//  Local definitions
BOOK list[5]=
{
       {"Title1", "Author1", {1, 26, 2001}},
       {"Title2", "Author2", {2, 27, 2002}},
       {"Title3", "Author3", {3, 28, 2003}},
       {"Title4", "Author4", {4, 29, 2004}},
       {"Title5", "Author5", {5, 30, 2005}}
};
//  Statements

       BOOK *p;
       HEADER head = {5, list};
       HEADER *pHead = &head;

       printList(p, pHead);
       printf("%s %c %d\n", pHead -> pAry[2].title, pHead -> pAry[2].author[0], pHead -> pAry[2].date.year );
return ;
}
void printBook( const BOOK *p)
{

char title[MAX_TITLE];
printf("%s %s %d %d %d\n", p -> title,
                        p -> author,
                        p -> date.month,
                        p -> date.day,
                        p -> date.year);

return ;
}
void printList( const BOOK *p, HEADER *pHead )
{

       for(p = pHead->pAry; p < pHead -> pAry + pHead -> counter ; p++)
       {
       printBook(p);
       }

}
/* OUTPUT:
Title1 Author1 1 26 2001
Title2 Author2 2 27 2002
Title3 Author3 3 28 2003
Title4 Author4 4 29 2004
Title5 Author5 5 30 2005
Title3 A 2003
*/

-Here is the final version that seemed to work. Thank you everyone for your help. @claudiu: I will try to play around with just struct when I have some free time. Unfortunately, she keeps piling us with more homework, so for now, I have to move on.