pointer to array of structures

Basically, I have a pointer to a pointer which points to an array of structures. I want to be able to dereference the pointer for individual elements in the structure.

But the code I have written doesn't work...

Code:

printf( "Name: %s %s\n", (**cust[i]).first, (**cust[i]).last);

... Can anyone please help??

Thanks

This is the full code for the program

Code:

#define _CRT_SECURE_NO_DEPRECATE
#include "airline.h"

void display_menu()
{ 
	printf( "=========================================================\n");
	printf( " To chose a function, enter its letter label:\n\n");
	printf( "a) Show assigned seats with passenger names\n"); printf( "b) Show list of empty seats\n");
	printf( "c) Assign a customer to a seat\n"); printf( "d) Edit customer details, for a specific seat\n");
	printf( "e) Delete a seat assignment\n"); printf( "f) Quit\n");
	printf( "=========================================================\n"); 
}

void options(pass* p) 
{ 
	char choice;
	for(;;) 
	{ 
		scanf("%c", &choice);
		switch (tolower(choice)) 
		{ 
		case 'a': 
			disp_assigned(&p);
			break; 
		case 'b': 
			//empty_seat();
			break; case 'c': 
			//allocate_seat();
			break; case 'd': 
			//edit_details(); 
			break; case 'e': 
			//delete_seat(); 
			break; case 'f': 
			exit(1); 
			break; 
		default: 
			printf( "Invalid option, please try again:\n"); fflush(stdin);
			break; 
		} 
	} 
} 

void disp_assigned(pass **cust) 
{ 
	int i; 

	for (i = 0; i < LIMIT; i++) 
	{ 
		if (!(**cust).flag)		
			printf("Seat unassigned");
		else
		printf( "\nThe details of passenger %d are:\n", i+1);
		printf( "Name: %s %s\n", (**cust).first, (**cust).last); 
	}
} 



int main() 
{ 
	pass	customers[LIMIT]; // An array of 14 (LIMIT) structures
	int		i; 

	for(i=0; i<LIMIT; i++)

    {
      customers[i].row = (i/2) + 1;   /* rows from 1 to 7 */
      customers[i].label = (i%2)?'B':'A';  /* odd i B, even A */
      customers[i].flag = 0;   /* seat empty */
      strcpy(customers[i].first, "Not ");
	  strcpy(customers[i].last, "Assigned");
	}

	
	for(i=0; i<LIMIT; i++) 
	{ 
	strcpy(customers[i].first, "Unassigned");
	}

display_menu(); 

options(&customers[LIMIT]); 

}

this is my header file:

Code:

/* airline.h */ 
#define _CRT_SECURE_NO_DEPRECATE

#include<stdio.h>
#include<string.h>

#define NAME 20
#define LIMIT 14
 
struct	passenger
{
int row;     /* from 1 to 7 */
char label;  /* A or B */
int flag;  //Use as a boolean - 1 if seat taken, 0 if not takes
char first[NAME];
char last[NAME];
};

typedef struct passenger pass;

/* function prototypes */ 

void display_menu(void);
void options(pass* p); 
void disp_assigned(pass** cust);

Hopefully that will help you guys to help me


Thanks again !

(&customers[LIMIT]); access out of bounds

ok, so how do i get round this problem??

you should access only members of the array inside the bounds from 0 to LIMIT-1

so what should i do about this line???

Code:

printf( "Name: %s %s\n", (**cust[i]).first, (**cust[i]).last);

> disp_assigned(&p);
Are you doing this because you have to (for your assignment), or because you think you need to (you don't).

> options(&customers[LIMIT]);
To pass the array, it's just
options( customers );

> printf( "Name: %s %s\n", (**cust[i]).first, (**cust[i]).last);
It you must use a pointer to a pointer, then you would do this
printf( "Name: %s %s\n", (*cust)[i].first, (*cust)[i].last );

Or you can remove a level of indirection by doing something like

Code:

void disp_assigned(pass **cust) 
{ 
	int i; 
	pass *temp = *cust;

	for (i = 0; i < LIMIT; i++) 
	{ 
		if (!temp[i].flag)		
			printf("Seat unassigned");
		else
		printf( "\nThe details of passenger %d are:\n", i+1);
		printf( "Name: %s %s\n", temp[i].first, temp[i].last); 
	}
}

I get ya!!! Thanks Salem!!! :-) :-)

OK I have modified my code to thus...

Code:

#define _CRT_SECURE_NO_DEPRECATE
#include "airline.h"

void display_menu()
{ 
	printf( "=========================================================\n");
	printf( " To chose a function, enter its letter label:\n\n");
	printf( "a) Show assigned seats with passenger names\n"); 
	printf( "b) Show list of empty seats\n");
	printf( "c) Assign a customer to a seat\n");
	printf( "d) Edit customer details, for a specific seat\n");
	printf( "e) Delete a seat assignment\n");
	printf( "f) Quit\n");
	printf( "=========================================================\n"); 
}

void options(pass* p) 
{ 
	int j=0;
	char choice;
	for(;;) 
	{ 
		scanf("%c", &choice);
		switch (tolower(choice)) 
		{ 
		case 'a': 
			for(j=0; j<LIMIT; j++)
			{
			disp_assigned(p, j);
			}
			break; 
		case 'b': 
			//empty_seat();
			break; case 'c': 
			//allocate_seat();
			break; case 'd': 
			//edit_details(); 
			break; case 'e': 
			//delete_seat(); 
			break; case 'f': 
			exit(1); 
			break; 
		default: 
			printf( "Invalid option, please try again:\n"); fflush(stdin);
			break; 
		} 
	} 
} 

void disp_assigned(pass *cust, int i) 
{
		if (cust[i].flag = 0)		
			printf("Seat %d is unassigned", i+1);
		else
		printf( "\nThe details of passenger %d are:\n", i+1);
		printf( "Name: %s %s\n", cust[i].first, cust[i].last); 
} 



int main() 
{ 
	pass	customers[LIMIT]; // An array of 14 (LIMIT) structures
	int		i; 

	for(i=0; i<LIMIT; i++)

    {
      customers[i].row = (i/2) + 1;   /* rows from 1 to 7 */
      customers[i].label = (i%2)?'B':'A';  /* odd i B, even A */
      customers[i].flag = 0;   /* seat empty */
      strcpy(customers[i].first, "Not ");
	  strcpy(customers[i].last, "Assigned");
	}

display_menu(); 

options(customers); 

}

header file...

Code:

/* airline.h */ 
#define _CRT_SECURE_NO_DEPRECATE

#include<stdio.h>
#include<string.h>

#define NAME 20
#define LIMIT 14
 
struct	passenger
{
int row;     /* from 1 to 7 */
char label;  /* A or B */
int flag;  //Use as a boolean - 1 if seat taken, 0 if not takes
char first[NAME];
char last[NAME];
};

typedef struct passenger pass;

/* function prototypes */ 

void display_menu(void);
void options(pass* p); 
void disp_assigned(pass* cust, int j);

This piece of code isnt working... its not getting the value what it should be. How do i rectify this?

Code:

if (cust[i].flag = 0)

thanks

= is for assignment, == is for comparison. You're doing a comparison, so use ==.

[edit] BTW, tolower() is in <ctype.h>. [/edit]

> if (cust[i].flag = 0)
Use ==

> printf( "\nThe details of passenger %d are:\n", i+1);
> printf( "Name: %s %s\n", cust[i].first, cust[i].last);
The second line will always be printed.
Use braces to make your intention explicit.

Code:

void display_menu()
{ 
	printf( "=========================================================\n");
	printf( " To chose a function, enter its letter label:\n\n");
	printf( "a) Show assigned seats with passenger names\n"); 
	printf( "b) Show list of empty seats\n");
	printf( "c) Assign a customer to a seat\n");
	printf( "d) Edit customer details, for a specific seat\n");
	printf( "e) Delete a seat assignment\n");
	printf( "f) Quit\n");
	printf( "=========================================================\n"); 
}

You don't really need that many printf() statements. Have a look at this: http://board.theprogrammingsite.com/viewtopic.php?t=85

Thanks guys! Much appreciated!!!

I've another problem - I got that other bit working fine now - thanks!! Its with the options function - theres no way of breaking out of the loop unless you exit. This is a problem since after executing a particular option from the menu I want the program to display the menu again except for choice (f) and to keep doing so until the program is terminated.

I'm a bit stuck as what to do. Any ideas or suggestions please??

Thanks!!!!!!!!!

Put a call to display_menu() in the for(;;) loop.