;; | ---------------------------------------------------------------------------
;; | MI_mfix
;; | ---------------------------------------------------------------------------
;; | Function : Modified fix function, handles negative numbers also.
;; | Argument : 'val - Value to be fix'ed
;; | Return   : The fix'ed value (always an integer)
;; | Update   : March 24, 1998
;; | e-mail   : rakesh.rao@4d-technologies.com 
;; | Web      : www.4d-technologies.com
;; | ---------------------------------------------------------------------------


(defun MI_mfix(val)

(if (minusp val)
	(1- (fix val))
	(fix val)
)
)

; Shell Sort

(defun MI_ssort (lst / number_items partition_size number_partitions first_index last_index
 unsorted count ptr_lst sorted_list i j t1 t2)

(if lst
(progn
	(setq
		number_items (length lst)
		partition_size number_items
		ptr_lst nil						; Pointer list
		count 0
		unsorted T						; Assume list is not sorted
	)

	(while (< count number_items)
		(setq
			ptr_lst (append ptr_lst (list count))	; built pointer list
			count (1+ count)
		)
	)

	(while unsorted
		(setq
			partition_size (fix (/ (1+ partition_size) 2))
			number_partitions (fix (/ number_items partition_size))
		)

		(if (= partition_size 1)
			(setq unsorted nil)		; assume list is sorted
		)

		(if (/= (rem number_items partition_size) 0)
			(setq number_partitions (1+ number_partitions))
		)
		(setq
			first_index 0
			i 1
		)
		(while (< i number_partitions)
			(setq last_index (+ first_index partition_size))

			(if (> last_index (- number_items partition_size))
				(setq last_index (- number_items partition_size))
			)

			; Loop thru and test (j) to (j+offset) in pointer list
			(setq j first_index)
			(while (< j last_index)
				(if (> (nth (nth j ptr_lst) lst)
					(nth (nth (+ j partition_size) ptr_lst) lst)
				)

				; Then swap items in pointer list
				(setq
					t1 (nth j ptr_lst)
					t2 (nth (+ j partition_size) ptr_lst)
					ptr_lst (subst t2 -1
								(subst t1 t2
									(subst -1 t1 ptr_lst)
								)
							)
					unsorted T
				))

				(setq j (1+ j))
			)

			(setq
				first_index (+ first_index partition_size)
				i (1+ i)
			)
		)
	)

	; Build new list using sorted pointers
	(setq count 0 sorted_list nil)
	(while (< count number_items)
		(setq
			sorted_list
					(append sorted_list			; Build updated list
						(list
							(nth
								(nth count ptr_lst)  ; Pointer
								lst
							)
						)
					)
			count (1+ count)
		)
	)
sorted_list
)
nil
)
)