how to Increment pointers with in a structure

[Yuga]

Hi,

I have a question,....he re is my program

struct list_el {
   int val;
   TEXT *acct_no;
   struct list_el * next;
};

typedef struct list_el item;

void main() {
   item * curr, * head;
   int i;
   long j = 1000;
   char ch[4];

   head = NULL;

   for(i=1;i<=10;i++) {
      curr = (item *)malloc(sizeof(item));
      curr->val = i;
      sprintf(ch,"%ld",j);
      curr->acct_no     =       (pTEXT)ch;
      curr->next  = head;
      head = curr;

j +=    500;
   }

   curr = head;

   while(curr) {
      printf("%s \t %d\n", curr->acct_no, curr->val);
      curr = curr->next ;
   }
free(curr);
}

o/p is
5500 10
5500 9
5500 8
5500 7
5500 6
5500 5
5500 4
5500 3
5500 2
5500 1

Expected is
1000 10
1500 11

Here TEXT is 4-byte unsigned integer (Character pointers to type TEXT).

Could you please help me to figure out this error? I am just a starter in C.
Hope my question is clear....

Thanks in advance..

[DeMan]

I think (and correct me when I'm wrong) that you want

*(curr->acct_no)  = (pTEXT)ch; //you want the value at the pointer to acct_no, not the pointer itself

Although your result is interesting, because 5500 is what we would expect the LAST value to be so I probably missed something

[horace1]

in the loop

   for(i=1;i<=10;i++) {
      curr = (item *)malloc(sizeof(item));
      curr->val = i;
      sprintf(ch,"%ld",j);
      curr->acct_no     =       (pTEXT)ch;
      curr->next  = head;
      head = curr;

j +=    500;
   }

j increments from 1000 to 5500 and on exit ch[] contains the string "5500". Each element of your list contains a pointer to ch[] so they ALL point to the same string, i.e. "5500".

you can have a char array in your structure an copy the string into it

struct list_el {
   int val;
   char acct_no[5];
   struct list_el * next;
};

note ch[] should be ch[5], 4 elements for the numeric characters and one for the terminating null character '\0'.
Otherwise acct_no could be an int

[chella]

Hi,

I have a question,....he re is my program

struct list_el {
   int val;
   TEXT *acct_no;
   struct list_el * next;
};

typedef struct list_el item;

void main() {
   item * curr, * head;
   int i;
   long j = 1000;
   char ch[4];

   head = NULL;

   for(i=1;i<=10;i++) {
      curr = (item *)malloc(sizeof(item));
      curr->val = i;
      sprintf(ch,"%ld",j);
      curr->acct_no     =       (pTEXT)ch;
      curr->next  = head;
      head = curr;

j +=    500;
   }

   curr = head;

   while(curr) {
      printf("%s \t %d\n", curr->acct_no, curr->val);
      curr = curr->next ;
   }
free(curr);
}

o/p is
5500 10
5500 9
5500 8
5500 7
5500 6
5500 5
5500 4
5500 3
5500 2
5500 1

Expected is
1000 10
1500 11

Here TEXT is 4-byte unsigned integer (Character pointers to type TEXT).

Could you please help me to figure out this error? I am just a starter in C.
Hope my question is clear....

Thanks in advance..

Hi yuga,
Is this the output u expect?

1000 1
1500 2
2000 3
.
.
.
.
5500 10

Regards,
Chella

[willakawill]

Hi. This is probably closer to your expected output:

struct list_el {
   int val;
   char acct_no[5];
   struct list_el * next;
};

typedef struct list_el item;

int main() {
   item * curr, * head;
   int i;
   long j = 1000;
   char ch[5];

   head = NULL;

   for(i=1;i<=10;i++) {
      curr = (item *)malloc(sizeof(item));
      curr->val = i;
      sprintf(ch,"%d",j);
      strcpy(curr->acct_no, ch);
      curr->next  = head;
      head = curr;

		j +=    500;
   }

   curr = head;

   while(curr) {
      printf("%s \t %d\n", curr->acct_no, curr->val);
      curr = curr->next ;
   }
	free(curr);
	getchar();
	return 0;
}

I eliminated any possible errors from your TEXT declaration and use strcpy() instead of

curr->acct_no = ch

which points all of your curr->acct_no pointers to the memory space that ch points to, so they all equal the final value stored there which is 5500.
ch, by the way, needs to be able to store 5 characters; the four from j and a null terminator.. main should always return an int

Well look at that! We all answered at once :)

[Yuga]

Excellent response ....once again thanks for your time...

Is it possible to use TEXT *acct_no in the above structure instead of char acct_no[5]. Because I need to pass these values to CTree API functions which accept only TEXT data types.

[willakawill]

Excellent response ....once again thanks for your time...

Is it possible to use TEXT *acct_no in the above structure instead of char acct_no[5]. Because I need to pass these values to CTree API functions which accept only TEXT data types.

There is an easy way to find out. Suck it and see
I did not have your declaration for this data type so I avoided it.