🚀 go-pugleaf

In article <1992Jul22.225838.13892@vlsisj.uucp>  
smadsen@leland.Stanford.EDU (Steve Madsen) writes:
> Here's an easy one. . .I'm stumped by the double asterisk declaration, 
> for example:
> 
> (int **)
> 
> I've tried to locate it in Chapter 3, 6 and 7 of NextStep Concepts, as 
> well as two different C manuals, so it's not a pure RTFM question (I 
> hope). . .

It's a double pointer.  (i.e. A pointer to another pointer.)  If you were  
to write:

	int	**temp;

It can be referenced several ways though.

	temp[x] would give you the x'th element of the pointer array.
		(which would be another pointer)

	temp would give you the first element (pointer)
		(such that temp has not been changed)

When mallocing one of these structures by yourself you will have to first  
malloc for the first pointer to the array and then malloc off all of the  
pointers to fill the array:

extern struct foo;
extern int numElements;
struct foo **fooItems;

{
	int i;

	fooItems = (struct foo **) malloc(sizeof(struct foo *) *  
numElements);
	for (i = 0; i < numElements; i++)
		fooItems[i] = (struct foo *) malloc(sizeof(struct foo));
}

You can procede down the pointer path a long ways.  The most I have ever  
used are five and I am not sure if there is a limitation as to how many  
one can have.

It happens to be referenced on pages 107-110 in K&R but they do not use a  
terribly good example to show a double pointer.

Mike Barthelemy
msb@chromagrafx.com