How do i assign internal error flags?

[kaniblu]

int dequeue() {
	int extracted_int;

	if ( tail_index == -1 ) {
		return NULL; // this is the part where i am stuck
	}
	else {
		extracted_int = queue[tail_index];
		tail_index = tail_index - 1;
	}
}

Hi. I'm a noob so even if this sounds ridiculous please don't be mad . I am trying to make a "dequeue" function that returns last element in the queue in int type. The problem is it needs to return some error flag when the queue is empty. The error flag must return internally so that it does not disrupt the entire program. It will only handled by the function that calls it. Assigning a very unlikely integer as an error flag could be done, or i can add another 'if' statement whenever i call the function, but it is too messy and repetitive. What is the clean way to do it? Thanks in advance

[Salem]

int dequeue ( int *errors ) {
  if ( ... ) {
    *errors = value;
  } else {
    *errors = 0;
  }
}

Pass an additional parameter, where you want the error result stored.

OR

static int lastError = 0;
int dequeue ( ) {
  if ( ... ) {
    lastError = value;
  } else {
    lastError = 0;
  }
}
int getError ( ) {
  return lastError;
}

Store an internal error state flag, and provide an additional function (or global variable like errno) for the external callers to use as they wish.

[CommonTater]

int dequeue() {
	int extracted_int;

	if ( tail_index == -1 ) {
		return NULL; // this is the part where i am stuck
	}
	else {
		extracted_int = queue[tail_index];
		tail_index = tail_index - 1;
	}
}

Hi. I'm a noob so even if this sounds ridiculous please don't be mad . I am trying to make a "dequeue" function that returns last element in the queue in int type. The problem is it needs to return some error flag when the queue is empty. The error flag must return internally so that it does not disrupt the entire program. It will only handled by the function that calls it. Assigning a very unlikely integer as an error flag could be done, or i can add another 'if' statement whenever i call the function, but it is too messy and repetitive. What is the clean way to do it? Thanks in advance

You almost had it....

int dequeue() {
	int extracted_int;

	if ( tail_index == -1 ) {
		return -1; 
	}
	else {
		extracted_int = queue[tail_index];
		tail_index = tail_index - 1;
                                return extracted_int;
	}
}



// call from main code
NextInt = dequeue();
if (NextInt < 0 )
  { 
     puts("queue is empty") 
     // deal with error here. 
}

The thing is to return the value you're after OR return some impossible value that you can watch for if it fails...