export sub shell_sort(x())
// Shell sort based on insertion sort

   local gap, i, j, first, last, tempi, tempj

   last = arraysize(x(),1)
   gap = int(last / 10) + 1
   while(TRUE)
	first = gap + 1
	for i = first to last
	   	tempi = x(i)
	    	j = i - gap
	    	while(TRUE)
			tempj = x(j)
			if tempi >= tempj then
		    		j = j + gap
		    		break
			end if
			x(j+gap) = tempj
			if j <= gap then
		    		break
			end if
			j = j - gap
	    	wend
	    	x(j) = tempi
	next i
	if gap = 1 then
	   	return
	else
	   	gap = int(gap / 3.5) + 1
	end if
   wend
end sub

if peek$("library") = "main" then

	clear screen
	
	ITEMS = 100
	dim numeros(ITEMS)
	
	for n = 1 to ITEMS
		numeros(n) = ran(ITEMS + 1)
	next n
	
	print time$
	shell_sort(numeros())
	print time$
	print "Press a key to see ordered numbers."
	inkey$
	
	for n = 1 to ITEMS
		print numeros(n),", ";
	next n

end if