OpenEuphoria

Re: gets() and "string" variable type

• Posted by Pete Lomax <petelomax at blue?onder.co?uk> Sep 15, 2007
• 595 views

Andy Drummond wrote:
> 
> What I would like to see addressed too is the possibility
> of a type "string", which is a string of bytes rather than
> a sequence of 32-bit words. The memory saving is significant,
> and the possibility of strings containing non-characters is
> completely removed.
>
> So - comments?
The s[i] op is of critical importance, which I now know from practical
experience, and supporting both 8-bit strings and 4-byte sequences would
inevitably lead to an overhead of about 20%. Still want?

Regards,
Pete
PS [OT] Can someone explain the last line of this snippet from be_execute.e:

    case L_RHS_SUBS_CHECK:
	if (!IS_SEQUENCE(*(object_ptr)pc[1])) {
	    goto subsfail;
	}
	/* FALL THROUGH */
    case L_RHS_SUBS: /* rhs subscript of a sequence */
	top = *(object_ptr)pc[2];  /* the subscript */
	obj_ptr = (object_ptr)SEQ_PTR(*(object_ptr)pc[1]);/* the sequence */
	if ((unsigned long)(top-1) >= ((s1_ptr)obj_ptr)->length) {
	    tpc = pc;
	    top = recover_rhs_subscript(top, (s1_ptr)obj_ptr);
	}
	top = (object)*(top + ((s1_ptr)obj_ptr)->base);

My grasp of C is limited and I do not actually understand how it knows to get
"top" from "base+top*4" rather than just "base+top". Not that it does not seem
logical, more "how does it know?"  Specifically, which parts of

   typedef long object;
   typedef object *object_ptr;

are applied/applicable when and where? Is it the earlier *(object_ptr) or the
latter (object)* or both or what?