arraybase 1
dim a = {-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20}
print formatRange(a)
print

dim b = {0,  1,  2,  4,  6,  7,  8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39}
print formatRange(b)
end

function formatRange (a)
	lb = a[?,]: ub = a[?]
	if ub = - 1 then return ""
	if lb = ub then return string(a[lb])
	rangeCount = 1
	range = string(a[lb])
	for i = lb + 1 to ub
		if a[i] = a[i - 1] + 1 then
			rangeCount += 1
		else
			if rangeCount = 1 then
				range += "," + string(a[i])
			else
				if rangeCount = 2 then
					rangeCount = 1
					range += "," + string(a[i-1]) + "," + string(a[i])
				else
					rangeCount = 1
					range += "-" + string(a[i-1]) + "," + string(a[i])
				end if
			end if
		end if
	next
	if rangeCount = 2 then
		range += "," + string(a[ub])
	else
		if rangeCount > 2 then range += "-" + string(a[ub])
	end if
	return range
end function