bubblesort.lua

--! Bubblesort has quadratic time complexity and should not be used in practice
return function(
	-- list to be sorted in-place
	list,
	-- function(a, b) -> truthy value if a < b
	less_than
)
	less_than = less_than or function(a, b)
		return a < b
	end
	for _ = 1, #list do
		for next = 2, #list do
			local previous = next - 1
			if less_than(list[next], list[previous]) then -- wrong order: previous > next
				list[next], list[previous] = list[previous], list[next]
			end
		end
	end
end