# Display the progress bar.
	#
	# `metadata`  can be used to pass a small amount of data to display after
	# the progress bar.
	fun display(metadata: nullable String) do
		var percent = current_percentage
		var p = current_value * max_columns / max_value
		printn "\r{percent}% ["
		for i in [1..max_columns] do
			if i < p then
				printn "="
			else if i == p then
				printn ">"
			else
				printn " "
			end
		end
		printn "]"
		if metadata != null then printn " ({metadata})"
	end