class IO::Event::PriorityHeap

def bubble_up(index)
	parent_index = (index - 1) / 2 # watch out, integer division!
	
	while index > 0 && @contents[index] < @contents[parent_index]
		# if the node has a smaller value than its parent, swap these nodes
		# to uphold the minheap invariant and update the index of the 'current'
		# node. If the node is already at index 0, we can also stop because that
		# is the root of the heap.
		# swap(index, parent_index)
		@contents[index], @contents[parent_index] = @contents[parent_index], @contents[index]
		
		index = parent_index
		parent_index = (index - 1) / 2 # watch out, integer division!
	end
end