going backward

[jk81]

this function suppose to move cusor to one space backward, but it gives me error. it compiles, but would not run...

definitions

typedef struct node{
   char chdata;
   struct node *link;
   struct node *prev;
   struct node *next;
}  node;
typedef struct node *position;

typedef struct bufferType{
   node *head;
   node *cursor;
   node *clipboard;
} bufferType;

typedef bufferType *bufferT;

backward function

void MoveCursorBackward(bufferT buffer)
{
position temp;

if(buffer -> head)
{
	while(temp -> next != buffer->cursor->next)
	{
		temp = temp -> next ;
	}
	buffer->cursor = temp;
}
}

[Cshot]

You didn't initialize temp

[Prelude]

You realize that your function returns sets buffer->cursor to the same spot it was originally, right? The implementation would work better like this:

void MoveCursorBackward(bufferT buffer)
{
  if(buffer->head)
  {
    position temp = buffer->head;

    while(temp->next != buffer->cursor)
    {
      temp = temp->next;
    }

    buffer->cursor = temp;
  }
}

Now it will work, but now you have to cover for problems such as when buffer->cursor is the same as buffer->head. While we're on the subject, since the list is double linked, why not just do this instead:

void MoveCursorBackward(bufferT buffer)
{
  if(buffer->head)
  {
    if(buffer->cursor->prev)
    {
      buffer->cursor = buffer->cursor->prev;
    }
  }
}

-Prelude