data structures C programs

				function head=sl_free(sl)
				% SL_FREE
				%
				%  head=SL_FREE(sl) frees the memory allocated to the singly linked
				%  list head.
				
				% Copyright (c) MathWorks Inc. 1998-2001. All rights reserved.
				
				if nargin				  error('one input argument required.');
				end
				if nargout				  error('one output argument required.');
				end
				
				head=sl.head;
				while head~=0
				  headnext=head.next;
				  free(head);
				  head=headnext;
				end
				sl.head=0;
				sl.tail=0;