Text 143, 59 rader
Skriven 2005-02-02 02:09:28 av Kurt Kuzba (1:261/38)
Ärende: [C] Resetting array pointer to 0
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From: "Kurt Kuzba" <kkuzba@centurytel.net>


From: TLewis@mcleodhealth.org
TL>  I am passing an array to a function by using a pointer.
TL>  After some processing in the function, I want to be able
TL>  to set the counter back to zero, so that I can do other
TL>  processing.  How can this be done?  I have included a very
TL>  rough example to show what I want to do.  In my example
TL>  below, in the function ListRecords, if the list is printed
TL>  again, then IC needs to be set back to zero.

    Roger answered most of the question.  In the event that your
 understanding of C is less than he believes, I'm going to go back
 further into the basics.
 C passes everything by value.  When you pass a pointer, the
 original pointer is not changed.  It remains the same.  Only the
 value of the pointer is passed, and the automatic pointer created
 by the called function is given the value of the pointer in the
 calling function.

TL>  int ListRecords(struct CardData *IC) {

 If you need to have the original pointer value for repeated
 iterations of incremental steps through an array, then you can
 just create another pointer and assign it the value of the one
 created in your function arguments.

int ListRecords(struct CardData *IC) {
   struct CardData *ICProcess;
   do {
      ICProcess = IC;
      whatever();
      while(bar)
         foo(ICProcess++);
   }  while(getkeypress());
   do {
      ICProcess = IC;
      while(whatever())
         foo(ICProcess++);
   }  while(getkeypress());
}

 If you are calling another function instead of interating through
 your data array a second time in the same function, then you don't
 need to do anything.  The original pointer in the calling function
 is still the same.  Calling the same or another function will pass
 the original pointer value to that called function, just as it did
 in the first instance.  To change the original pointer, you would
 need to have the pointer to that pointer.

]<urt

>  kkuzba@centurytel.net   http://home.centurytel.net/kkuzba
>  Governing a large country is like frying a small fish.
>  (Tao te Ching #60)

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